If you want to do something about “wasted” space in an index what are the differences that you need to consider between the following three options (for the purposes of the article I’m ignoring “rebuild” and “rebuild online”):
alter index xxx coalesce;
alter index xxx shrink space compact;
alter index xxx shrink space;
Looking at the notes in a script I wrote a “few” years ago it seems that I haven’t looked at a comparison between the coalesce option and the shrink space options since 10.2.0.3 and I suspect things may have changed since then, so I’ve discarded the results that I had recorded (in 2012) and started again with 19.11.0.0
Background
I’ve been looking at the “deferred global index maintenance” in the last couple of weeks which is why I was toying with the idea of writing something about shrinking indexes and how it differs from coalescing them when an Oracle Forum question (needs MOS account) produced the (slightly surprising) suggestion to use coalesce – so I decided it was time to (re-)test, write and publish.
RTFM
First a few bullet points from the 19c SQL reference manual under “alter index”, or following the links from there to the “shrink clause”, or the database administration reference
- Specify
COALESCE
to instruct Oracle Database to merge the contents of index blocks where possible to free blocks for reuse.
- Use this [shrink] clause to compact the index segments. Specifying
ALTER
INDEX
… SHRINK SPACE
COMPACT
is equivalent to specifying ALTER
INDEX
… COALESCE
.
- If you specify
COMPACT
, then Oracle Database only defragments the segment space … The database does not readjust the high water mark and does not release the space immediately.
- Can’t shrink space for bitmap join indexes or function-based indexes.
- Segment shrink is an online, in-place operation. DML operations and queries can be issued during the data movement phase of segment shrink. Concurrent DML operations are blocked for a short time at the end of the shrink operation when the space is deallocated.
- Shrink operations can be performed only on segments in locally managed tablespaces with automatic segment space management (ASSM).
- As with other DDL operations, segment shrink causes subsequent SQL statements to be reparsed because of invalidation of cursors unless you specify the
COMPACT
clause.
As with many little features of Oracle it’s quite hard to pick up a complete and cohesive statement of what something does and what impact it might have. Some of the bullet points above are generic about shrinking segments, and may not be totally accurate for shrinking only an index – will it invalidate cursors, or does that happen only when you shrink a table used by the cursor, or only when you shrink an index that’s used by the cursor.
If you do read through the links you also notice that I’ve omitted several points from the generic shrink details that are not relevant for indexes (for example the requirement to enable row movement), and have only mentioned the restrictions which are explicitly referenced in the “shrink clause” for indexes.
What do we need to know?
Some of the fairly typical bits of information we might need to know about a “house-keeping” task like coalesce/shrink are:
- How much work does it do, and of what type?
- What exactly is the benefit we might get for the work done
- What side-effects do we have to consider (locking, cursor invalidation etc.)
- What side effects might show up if the process fails in mid-stream.
In the case of coalesce/shrink for indexes, a few specific questions would be:
- Is “shrink space compact” really equivalent to “coalesce”
- Are the operations “online” or only “nearly online”.
- If shrink/coalesce is moving index entries around and moving index blocks around what happens if a session wants to insert an index entry into a leaf block that’s currently being “transferred” into another leaf block.
- If it’s a big index that needs several minutes (or more) to shrink/coalesce, could ongoing transactions cause index leaf block splits that produce unexpected effects when Oracle tried to drop the highwater mark.
- How big an index, and how long would the test have to take, and what degree of concurrency, and how (un)lucky would you have to be to hit a moment when something “strange” happened.
Finally – what tools would be helpful. Initially we might just look at:
- session stats – to see what work we do
- the dbms_space package – to check segment space usage pre and post.
- the treedump event – to get a detailed picture of the index
Based on what we see we might feel the need to dig a little deeper with:
- v$enqueue_stats
- v$rollstat (rollback (undo) segment usage)
- SQL tracing with wait states
- Enqueue (lock) tracing
- redo dumps
The basic model
Here’s a little script to create a model that we can use for testing. Because of the stated requirement of the shrink space command I’ll just point out that the default tablespace should be using automatic segment space management (ASSM), my tablespace is also defined to use 1MB uniform extents:
rem
rem Script: shrink_coalesce.sql
rem Author: Jonathan Lewis
rem Dated: May 2012
rem
rem Last tested:
rem 19.11.0.0
rem
execute dbms_random.seed(0)
create table t1 (
v1 varchar2(7)
);
create index t1_i1 on t1(v1);
begin
for i in 1..1e6 loop
insert into t1(v1) values(
to_char(1e6 + trunc(dbms_random.value(0,100000)))
);
end loop;
end;
/
commit;
column ind_id new_value m_ind_id
select object_id ind_id
from user_objects
where object_name = 'T1_I1'
;
alter session set tracefile_identifier = 'creation';
alter session set events 'immediate trace name treedump level &m_ind_id';
alter system flush buffer_cache;
pause Check the tree dump and pick a leaf block to dump
-- alter system dump datafile &&datafile block &&block_id;
alter system dump datafile 36 block 5429;
prompt ========================
prompt Deleting 4 rows out of 5
prompt ========================
delete from t1
where mod(v1,5) != 0
;
commit;
alter session set tracefile_identifier = 'deletion';
alter session set events 'immediate trace name treedump level &m_ind_id';
alter system flush buffer_cache;
-- pause Check the tree dump and pick a leaf block to dump
-- alter system dump datafile &&datafile block &&block_id;
alter system dump datafile 36 block 5429;
begin
dbms_stats.gather_table_stats(
ownname => user,
tabname =>'T1',
method_opt => 'for all columns size 1',
cascade => true
);
end;
/
select
rows_per_block,
count(*) block_count
from (
select
/*+
dynamic_sampling(0)
index_ffs(t1,t1_i1)
noparallel_index(t,t1_i1)
*/
sys_op_lbid( &m_ind_id ,'L',t1.rowid) as block_id,
count(*) as rows_per_block
from
t1
group by
sys_op_lbid( &m_ind_id ,'L',t1.rowid)
)
group by
rows_per_block
order by
rows_per_block
;
@@dbms_space_use_assm_embedded test_user t1_i1 index
Unusually (for me) I’ve created the data by inserting rows one at a time after creating the index. This is to avoid starting from a “perfect” index i.e. one where the physical ordering of the leaf blocks is closely correlated with the logical ordering of the leaf blocks, and where the leaf blocks are very well packed.
With a single session inserting rows there will be a visible pattern to the choice that Oracle makes for “the next avilable free block” when it needs to do a leaf block split, but with the random value insertions there won’t be a pattern in “which block just split” so when you walk the index in key order the steps from one leaf block to the next will jump fairly randomly around the segment.
The table starts at 1,000,000 rows, but ends up with about 200,000 after deletion and an index where roughly 80% of the rows in each leaf block have been deleted. So that we know what state the tests start from I’ve done a treedump of the index before and after the delete (and included a pause in the script to allow you to find a dump to block from the treedump if you want to) with the following results:
Before:
----- begin tree dump
branch: 0x9000104 150995204 (0: nrow: 8, level: 2)
branch: 0x9000438 150996024 (-1: nrow: 401, level: 1)
leaf: 0x900016d 150995309 (-1: row:222.222 avs:3778)
leaf: 0x900154e 151000398 (0: row:218.218 avs:3854)
leaf: 0x9000abd 150997693 (1: row:219.219 avs:3835)
leaf: 0x900153e 151000382 (2: row:209.209 avs:4025)
leaf: 0x900058d 150996365 (3: row:230.230 avs:3626)
leaf: 0x90013a8 150999976 (4: row:229.229 avs:3645)
leaf: 0x9000ae1 150997729 (5: row:411.411 avs:187)
leaf: 0x900031c 150995740 (6: row:227.227 avs:3683)
leaf: 0x90014d3 151000275 (7: row:229.229 avs:3645)
leaf: 0x9000aec 150997740 (8: row:226.226 avs:3702)
leaf: 0x90014f3 151000307 (9: row:226.226 avs:3702)
leaf: 0x9000593 150996371 (10: row:219.219 avs:3835)
leaf: 0x9001559 151000409 (11: row:223.223 avs:3759)
leaf: 0x9000a9d 150997661 (12: row:210.210 avs:4006)
leaf: 0x900152e 151000366 (13: row:215.215 avs:3911)
leaf: 0x900018a 150995338 (14: row:258.258 avs:3094)
...
After:
----- begin tree dump
branch: 0x9000104 150995204 (0: nrow: 8, level: 2)
branch: 0x9000438 150996024 (-1: nrow: 401, level: 1)
leaf: 0x900016d 150995309 (-1: row:222.47 avs:3778)
leaf: 0x900154e 151000398 (0: row:218.52 avs:3854)
leaf: 0x9000abd 150997693 (1: row:219.44 avs:3835)
leaf: 0x900153e 151000382 (2: row:209.43 avs:4025)
leaf: 0x900058d 150996365 (3: row:230.44 avs:3626)
leaf: 0x90013a8 150999976 (4: row:229.45 avs:3645)
leaf: 0x9000ae1 150997729 (5: row:411.88 avs:187)
leaf: 0x900031c 150995740 (6: row:227.50 avs:3683)
leaf: 0x90014d3 151000275 (7: row:229.42 avs:3645)
leaf: 0x9000aec 150997740 (8: row:226.46 avs:3702)
leaf: 0x90014f3 151000307 (9: row:226.57 avs:3702)
leaf: 0x9000593 150996371 (10: row:219.46 avs:3835)
leaf: 0x9001559 151000409 (11: row:223.54 avs:3759)
leaf: 0x9000a9d 150997661 (12: row:210.33 avs:4006)
leaf: 0x900152e 151000366 (13: row:215.30 avs:3911)
leaf: 0x900018a 150995338 (14: row:258.52 avs:3094)
...
leaf: 0x900077f 150996863 (398: row:356.64 avs:1232)
leaf: 0x9000d67 150998375 (399: row:327.62 avs:1783)
branch: 0x9000e45 150998597 (0: nrow: 378, level: 1)
leaf: 0x900047a 150996090 (-1: row:342.86 avs:1498)
leaf: 0x9000d46 150998342 (0: row:357.60 avs:1213)
...
...
leaf: 0x9000607 150996487 (492: row:369.80 avs:985)
leaf: 0x9000c60 150998112 (493: row:395.70 avs:491)
branch: 0x9000c68 150998120 (6: nrow: 503, level: 1)
leaf: 0x90001b2 150995378 (-1: row:235.60 avs:3531)
leaf: 0x9001323 150999843 (0: row:230.54 avs:3626)
The “before” section is just the first few lines of 3,538 and shows us that we have a root block with 8 branch blocks (numbered from -1 to +6), and the first branch block holds 401 leaf blocks(numbered from -1 to 399), and the first leaf block starts with 222 index entries (in its row directory) of which, we learn from the “after” section, 47 (i.e. roughly 20%) are still “in use” after the delete. The “after” section adds in a few extra lines from the treedump, around branch block 0 and branch block 6.
In passing, if I were to execute a new transaction that inserted a new index entry into the first leaf block Oracle would tidy its directory and the start of the tree dump would look like the following:
branch: 0x9000104 150995204 (0: nrow: 8, level: 2)
branch: 0x9000438 150996024 (-1: nrow: 401, level: 1)
leaf: 0x900016d 150995309 (-1: row:48.48 avs:7084)
leaf: 0x900154e 151000398 (0: row:218.52 avs:3854)
After the initial big insert many of the leaf blocks hold around 220 rows but we can see one leaf block of the initial 16 holding 411 rows. Allowing for the 9 blocks that aren’t leaf blocks we can calculate that we should see an average of approximately 1,000,000/3,529 = 283 rows per leaf block; the variation is the result of leaf block “50/50” splits. When a leaf block is full the next attempted insert causes Oracle to attach a new leaf block to the structure and share the existing entries fairly evenly between the two blocks (although there is one special case, the so-called “90/10” split that can happen when you insert a new high value into the highest value leaf block). The shares are not exactly equal because Oracle has to insert a new pointer in the parent branch block at the same time and may be able to reduce the size of this pointer by moving the split point some way from the “fair share” 50/50 point.
Of course, there’s also some variation in the content of the leaf blocks because they tend to start refilling shortly after they’ve split, so it can be quite instructive (when your system reaches “steady state” to produce a “histogram” of leaf contents – which is what the last SQL statement in my setup script is about, with the following results:
Click here to expand the index histogram report
ROWS_PER_BLOCK BLOCK_COUNT
-------------- -----------
24 1
26 1
27 1
28 5
29 5
30 7
31 11
32 11
33 26
34 23
35 28
36 28
37 49
38 47
39 43
40 49
41 62
42 73
43 81
44 92
45 98
46 91
47 117
48 104
49 124
50 124
51 117
52 114
53 106
54 123
55 109
56 104
57 96
58 84
59 70
60 95
61 57
62 73
63 77
64 74
65 66
66 56
67 52
68 54
69 59
70 44
71 56
72 49
73 47
74 51
75 27
76 34
77 29
78 27
79 25
80 27
81 28
82 26
83 16
84 23
85 16
86 18
87 11
88 19
89 16
90 10
91 11
92 5
93 5
94 2
95 3
96 4
97 3
99 3
100 4
103 1
107 1
119 1
78 rows selected.
The result (because it’s randomly arriving values) is fairly close to the bell curve of the Normal distribution centred at around 50 rows. There’s a fairly long tail up to 119 rows, but that’s probably there in this case because the index state hadn’t quite reached steady state before I did the big delete.
Having dumped a leaf block I know that a completely packed leaf block could hold 420 rows, and at pctfree 10 that would mean 378 rows, and at 70% utilisation (which is what I expect with random arrival) an average of 294 rows generating an index of 3,400 leaf blocks rather than the 3,529 I got. (Again, I think the divergence from expectation are probably related to needing more time to get to steady state.)
The final call in the script is to a stripped down version of some code I published a few years back; the relevance of the numbers when applied to indexes is described in this blog note and the numbers were as follows:
Unformatted : 62 / 507,904
Freespace 1 ( 0 - 25% free) : 0 / 0
Freespace 2 ( 25 - 50% free) : 45 / 368,640
Freespace 3 ( 50 - 75% free) : 0 / 0
Freespace 4 ( 75 - 100% free) : 0 / 0
Full : 3,545 / 29,040,640
PL/SQL procedure successfully completed.
Segment Total blocks: 3,712
Object Unused blocks: 0
PL/SQL procedure successfully completed.
Freespace 2 is the label given to the set of blocks that are available for use (empty) whether or not they are in the index structure. Given the pattern of work so far it’s fairly safe to assume that in this case they are “formatted but not yet attached to the index structure”.
A quick arithmetic check highlights an apparent discrepancy: 62 + 45 + 3,545 = 3,652, which is 60 blocks short of the number in the segment; but that’s okay because I have 29 uniform extents of 1MB in the segment, which means 2 space management level 1 bitmap blocks per extent plus one level 2 bitmap block, plus the segment header / level 3 bitmap block – for a total of 60 space management blocks.
The thing I’m not keen on is that the space management blocks are reporting 3,545 Full blocks, when the treedump showed 3,538 blocks – where did the extra 7 come from. But I’m not going to worry about that for this blog note.
Tests and results
The following block of code shows the full set of logging and tracing that I did – though I didn’t use every single diagnostic in every single run – for each of the three options. The code in this case is wrapped around a call to coalesce:
alter session set tracefile_identifier = 'coalesce';
alter session set events 'immediate trace name treedump level &m_ind_id';
execute snap_enqueues.start_snap
execute snap_rollstats.start_snap
execute snap_my_stats.start_snap
execute snap_redo.start_snap
alter session set events 'trace[ksq] disk=medium';
column current_scn new_value start_scn
select to_char(current_scn,'9999999999999999') current_scn from v$database;
alter index t1_i1 coalesce;
column current_scn new_value end_scn
select to_char(current_scn,'9999999999999999') current_scn from v$database;
alter session set events 'trace[ksq] off';
execute snap_redo.end_snap
execute snap_my_stats.end_snap
execute snap_rollstats.end_snap
execute snap_enqueues.end_snap
alter session set events 'immediate trace name treedump level &m_ind_id';
alter session set tracefile_identifier='coalesce_redo';
alter system dump redo scn min &start_scn scn max &end_scn ;
alter session set tracefile_identifier='';
@@dbms_space_use_assm_embedded test_user t1_i1 index
@@index_histogram_embedded t1 t1_i1 &m_ind_id
Working from the top down:
- Set an identifier to include in the trace file name.
- take a starting treedump (which will go to that trace file)
- take starting snapshots of
- system level enqueue stats
- system leve rollback stats
- my session activity stats
- a subset of session stats relating to redo
- enable tracing of Enqueues (locks)
- capture the current SCN in a define variable
- coalesce the index
- capture the final SCN in a define variable
- report the change in the 4 sets of stats listed above
- save the ending treedump to the trace file
- set a new identifier for the tracefile name
- dump all the redo generated while the coalesce was going on to the new tracefile
- Call a script to report the space usage for the index segment
- Call a script to report the histogram of leaf block usage again
The starting treedump will match the “post-delete” treedump above, of course, but it’s just a convenience for each test to have its before and after treedumps in the same trace file; and the redo dump (which will include redo from every active session) is so large – about 275MB – that it’s a good idea to keep it separate from the treedumps and enqueue trace.
The histogram script is just a wrapper for the two sys_op_lbid() queries shown earlier on. The space usage script is one we’ve already met.
A test run takes only a couple of minutes – and most of the time is spent inserting 1M rows into an indexed table one at a time. (The time it took to analyze the logs, traces and dumps is much longer, and the time to summarize and write up the results is longer still!)
Here, then, are the most interesting details from the three tests. Some of the comments I make are not immediately “proved” by the results I’m showing, but the volume of data required to supply corroborative evidence would become excessive and very boring.
Coalesce
The first “big picture” item to look at after the coalesce is the space usage:
Unformatted : 62 / 507,904
Freespace 1 ( 0 - 25% free) : 0 / 0
Freespace 2 ( 25 - 50% free) : 3,037 / 24,879,104
Freespace 3 ( 50 - 75% free) : 0 / 0
Freespace 4 ( 75 - 100% free) : 0 / 0
Full : 553 / 4,530,176
PL/SQL procedure successfully completed.
Segment Total blocks: 3,712
Object Unused blocks: 0
The index segment is 3,712 blocks, of which 553 are “Full”, and 3,037 are in the “Freespace 2” state which, for indexes, means they are empty and available for reuse. The coalesce hasn’t released space back to the tablespace but we can’t tell from these figures whether the 553 blocks full blocks are packed into the “bottom end” of the segment or scattered across the entire length of the segment. Or, to view it another way, the figues don’t tell us whether Oracle has been shuffling rows without completely re-arranging the block linkages or whether it’s also been moving rows so that it can reconnect leaf blocks in a way that leaves all the empty blocks above a notional highwater mark.
We can dig a little deeper by looking at the treedump:
branch: 0x9000104 150995204 (0: nrow: 8, level: 2)
branch: 0x9000438 150996024 (-1: nrow: 64, level: 1)
leaf: 0x900016d 150995309 (-1: row:377.377 avs:833)
leaf: 0x90014d3 151000275 (0: row:377.377 avs:833)
leaf: 0x900118c 150999436 (1: row:377.377 avs:833)
leaf: 0x9000370 150995824 (2: row:377.377 avs:833)
...
leaf: 0x9000d2f 150998319 (61: row:377.377 avs:833)
leaf: 0x9000d67 150998375 (62: row:114.114 avs:5830)
branch: 0x9000e45 150998597 (0: nrow: 59, level: 1)
leaf: 0x900047a 150996090 (-1: row:377.377 avs:833)
leaf: 0x9000725 150996773 (0: row:377.377 avs:833)
...
...
leaf: 0x9000a05 150997509 (67: row:377.377 avs:833)
leaf: 0x900030d 150995725 (68: row:376.376 avs:852)
branch: 0x9000c68 150998120 (6: nrow: 76, level: 1)
leaf: 0x90001b2 150995378 (-1: row:60.60 avs:6856)
leaf: 0x9001323 150999843 (0: row:377.377 avs:833)
The root block is still reporting the same number of level 1 branch blocks, but the branch blocks report far fewer leaf blocks each. Most of the leaf blocks report 377 index entries, but the first and last leaf blocks of each branch tend to show fewer.
I pointed out earlier on that with pctfree 10 we’d get 378 rows per leaf block if we recreated the index, but it looks like there’s a little overhead I didn’t allow for and we’ve actually got 377 from the coalesce. You’ll notice that a coalesce will actually reduce the number of index entries in a leaf block if it exceeds the limit set by pctfree (remember how the original treedump extracts showed one leaf block with 411 entries).
Coalesce does not act “across” branch blocks, which is why (a) the number of branch blocks is unchanged, and (b) why the number of rows in the last leaf block of a branch block may have fewer rows than the typical leaf blocks – coalesce will not move rows from the first leaf block of the next branch.
I’ve included a few lines from around the branches numbered 0 and 6 in this extract. If you compare them with the treedump taken just after the delete you’ll see that the coalesce has copied rows back from the second (0th) leaf of branch 0 into the first (-1th) leaf , but not from the second (0th) leaf into the first (-1th) leaf of branch 6. I don’t know why this is but perhaps it’s something to do with the relative number of rows in the first and second (-1th and 0th) leaf blocks – the same behaviour showed up at the start of branch 3 where the two leaf blocks had 58 and 63 rows respectively.
Getting back to the question of whether the “Freespace 2” blocks reported by the space usage procedure are still in the structure or whether they have been unlinked – the number of leaf blocks reported per branch block is fairly convincing – the empty leaf blocks have been detached from the structure and are simply flagged as free blocks in the space management level 1 bitmap. We could do a quick check of all the branch blocks (grep ” branch” from the trace file):
branch: 0x9000104 150995204 (0: nrow: 8, level: 2)
branch: 0x9000438 150996024 (-1: nrow: 64, level: 1)
branch: 0x9000e45 150998597 (0: nrow: 59, level: 1)
branch: 0x90007d1 150996945 (1: nrow: 61, level: 1)
branch: 0x9000e8a 150998666 (2: nrow: 66, level: 1)
branch: 0x900043c 150996028 (3: nrow: 70, level: 1)
branch: 0x9000e18 150998552 (4: nrow: 70, level: 1)
branch: 0x900073d 150996797 (5: nrow: 70, level: 1)
branch: 0x9000c68 150998120 (6: nrow: 76, level: 1)
Add up the nrow for the level 1 branches and you get 536; add 9 for the branch blocks themselves and you get 545 – and the space usage report says 553 (an unexplained error of 8 which I’ll get round to worrying about one day; I wonder if there’s any significance in how close it is to the error of 7 that we had before the coalesce).
We can learn more from the tree dump by walking the leaf blocks in order and checking their block addresses.
- The first leaf block of the first level 1 branch block is 0x900016d before and after the coalesce.
- The second leaf block of the this branch block is 0x90014d3 after the coalesce, but that was the address of leaf block number 7 before the coalesce.
- The third leaf block is 0x900118c after the coalesce but was leaf block number 15 before the coalesce.
The coalesce has been walking the index in order, copying rows back to earlier leaf blocks and unlinking the block it’s working on if it becomes empty. The ultimate effect of this is that the final set of index leaf blocks isn’t compacted into the smallest contiguous space possible, it’s scattered just as widely and randomly across the whole segment as it was before the coalesce.
We could go one step further to demonstrate this scattering. Extract all the lines for leaf blocks from the treedump and sort them into order. Since I’m using 1MB exents I’d like to see (nearly) 128 consecutive block addresses in order before a possible jump to a block in the next extent but here are first few addresses when I do the experiment:
leaf: 0x9000105 150995205 (59: row:377.377 avs:833)
leaf: 0x9000108 150995208 (3: row:377.377 avs:833)
leaf: 0x900010a 150995210 (52: row:377.377 avs:833)
leaf: 0x9000115 150995221 (12: row:377.377 avs:833)
leaf: 0x9000117 150995223 (63: row:377.377 avs:833)
leaf: 0x900011e 150995230 (3: row:377.377 avs:833)
leaf: 0x900011f 150995231 (53: row:377.377 avs:833)
leaf: 0x900012b 150995243 (34: row:377.377 avs:833)
leaf: 0x9000137 150995255 (34: row:377.377 avs:833)
leaf: 0x900013a 150995258 (63: row:377.377 avs:833)
leaf: 0x900013d 150995261 (43: row:377.377 avs:833)
You don’t have to be skilled at reading hex numbers to see all the gaps between the used block addresses.
Coalesce – Transactions
We now know where the index has got to, so the next question is how did it get there. The snapshot showing the change in rollback statistics (v$rollstat) is revealing.
USN Ex Size K HWM K Opt K Writes Gets Waits Shr Grow Shr K Act K
---- -- ------ ----- ----- ------ ---- ----- --- ---- ----- ------
0 0 0 0 0 0 1 0 0 0 0 0
1 5 5120 0 0 5101714 1199 0 0 5 0 -28446
2 6 6144 0 0 5278032 1245 0 0 6 0 275
3 7 7168 0 0 5834744 1365 0 0 7 0 -1492
4 1 8192 0 0 5944580 1378 0 0 1 0 -17281
5 6 6144 0 0 5126248 1203 0 0 6 0 303
6 4 4096 0 0 5076808 1189 0 0 4 0 -72
7 6 6144 0 0 5244984 1239 0 0 6 0 127
8 7 7168 0 0 5818394 1363 0 0 7 0 263
9 7 7168 0 0 6017230 1401 0 0 7 0 213
10 1 8192 8192 0 5060154 1178 0 0 1 0 -54488
My session was the only one active on the system, and it’s only a small play system so the only undo segments it has are the basic 10 that appear when you create the database (plus the one rollback segment in the SYSTEM tablespace).
The critical numbers are the writes (bytes) and gets (blocks), which tell us that our single operation has behaved as a number of individual transactions that have been starting in different undo segments.
Given the fairly even spread of bytes written it’s a good bet that we’re seeing a fairly large number of fairly small transactions. We can corroborate this by looking at the snapshot of enqueue (lock) stats (v$enqueue_stats):
Type Requests Waits Success Failed Wait m/s Reason
---- -------- ----- ------- ------ -------- ------
CF 2 0 2 0 0 contention
XR 1 0 1 0 0 database force logging
TM 1 0 1 0 0 contention
TX 3,051 0 3,051 0 0 contention
HW 50 0 50 0 0 contention
TT 50 0 50 0 0 contention
CU 24 0 24 0 0 contention
OD 1 0 1 0 0 Serializing DDLs
JG 126 0 126 0 0 queue lock
JG 12 0 12 0 0 q mem clnup lck
JG 126 0 126 0 0 contention
The enqueue we’re interested in is the TX (transaction) enqueue – and Oracle reports more than 3,000 of them in the interval. (That’s interestingly close to the number of blocks in the index or, to be even fussier, the number of leaf blocks that have been emptied – but that might be a coincidence.)
You’ll notice, though, that there’s only 1 TM (table) lock request. Whatever else we’re doing we’re not locking and unlocking the table on every single transaction – so we need to find out what that lock is and whether it might be a threat to our application (a TM lock in mode 4, 5, or 6, held for the duration would be a disaster). And that’s why I enabled the ksq (enqueue) trace – here’s the extract from the trace file showing the acquisition of the TM lock.
2022-09-02 11:36:57.645*:ksq.c@9175:ksqgtlctx(): *** TM-000230A3-00000000-0039DED3-00000000 mode=2 flags=0x401 why=173 timeout=0 ***
2022-09-02 11:36:57.645*:ksq.c@9183:ksqgtlctx(): xcb=0x9bbeec68, ktcdix=2147483647 topxcb=0x9bbeec68 ktcipt(topxcb)=0x0
2022-09-02 11:36:57.645*:ksq.c@9203:ksqgtlctx(): ksqgtlctx: Initializing lock structure
2022-09-02 11:36:57.645*:ksq.c@9324:ksqgtlctx(): DID DUMP START
2022-09-02 11:36:57.645*:ksq.c@9328:ksqgtlctx(): ksqlkdid: 0001-0029-0000013C
2022-09-02 11:36:57.645*:ksq.c@9333:ksqgtlctx(): tktcmydid: 0001-0029-0000013C
2022-09-02 11:36:57.645*:ksq.c@9337:ksqgtlctx(): tksusesdi: 0000-0000-00000000
2022-09-02 11:36:57.645*:ksq.c@9341:ksqgtlctx(): tksusetxn: 0001-0029-0000013C
2022-09-02 11:36:57.645*:ksq.c@9343:ksqgtlctx(): DID DUMP END
2022-09-02 11:36:57.645*:ksq.c@9517:ksqgtlctx(): ksqgtlctx: did not find link
2022-09-02 11:36:57.645*:ksq.c@9687:ksqgtlctx(): ksqgtlctx: updated ksqlrar1, ksqlrar:0x9e7f7cb8, ksqlral:(nil)
2022-09-02 11:36:57.645*:ksq.c@9841:ksqgtlctx(): ksqgtlctx: updated ksqlral, ksqlral:0x9bac7bc0, res:0x9e7f7cb8
2022-09-02 11:36:57.645*:ksq.c@9851:ksqgtlctx(): ksqgtlctx: updated lock mode, mode:2 req:0
2022-09-02 11:36:57.645*:ksq.c@9960:ksqgtlctx(): SUCCESS
I’ve highlighted the line where the TM lock appears, reporting an “id1” of 000230A3, which is the object_id of the table t1. Take note of the other highlighted line which gives the address of the resource element used (res: 0x9e7f7cb8) because we can use this to find where the lock is released:
2022-09-02 11:36:58.735*:ksq.c@10367:ksqrcli_int(): ksqrcli_int: updated ksqlral, ksqlral:0x9bac7bc0, res:0x9e7f7cb8
2022-09-02 11:36:58.735*:ksq.c@10501:ksqrcli_int(): returns 0
This appears in the last few lines of the ksq trace, after the appearance of several thousand (brief) TX locks that have been acquired and released. So there is a low-impact table lock held for the duration of the coalesce that is not going to stop other sessions from updating the table (and its indexes).
There was one other lock released after the TM lock:
2022-09-02 11:36:58.769*:ksq.c@10367:ksqrcli_int(): ksqrcli_int: updated ksqlral, ksqlral:0x9e6b2370, res:0x9e7f0788
2022-09-02 11:36:58.769*:ksq.c@10501:ksqrcli_int(): returns 0
Working backwards using the resource address we find that this was an OD lock, taken immediately after the TM lock:
2022-09-02 11:36:57.645*:ksq.c@9175:ksqgtlctx(): *** OD-000230A4-00000000-0039DED3-00000000 mode=4 flags=0x10001 why=277 timeout=0 ***
2022-09-02 11:36:57.645*:ksq.c@9183:ksqgtlctx(): xcb=0x9bbeec68, ktcdix=2147483647 topxcb=0x9bbeec68 ktcipt(topxcb)=0x0
2022-09-02 11:36:57.645*:ksq.c@9203:ksqgtlctx(): ksqgtlctx: Initializing lock structure
2022-09-02 11:36:57.645*:ksq.c@9324:ksqgtlctx(): DID DUMP START
2022-09-02 11:36:57.645*:ksq.c@9328:ksqgtlctx(): ksqlkdid: 0001-0029-0000013C
2022-09-02 11:36:57.645*:ksq.c@9333:ksqgtlctx(): tktcmydid: 0001-0029-0000013C
2022-09-02 11:36:57.645*:ksq.c@9337:ksqgtlctx(): tksusesdi: 0000-0000-00000000
2022-09-02 11:36:57.645*:ksq.c@9341:ksqgtlctx(): tksusetxn: 0001-0029-0000013C
2022-09-02 11:36:57.645*:ksq.c@9343:ksqgtlctx(): DID DUMP END
2022-09-02 11:36:57.645*:ksq.c@9517:ksqgtlctx(): ksqgtlctx: did not find link
2022-09-02 11:36:57.645*:ksq.c@9687:ksqgtlctx(): ksqgtlctx: updated ksqlrar1, ksqlrar:0x9e7f0788, ksqlral:(nil)
2022-09-02 11:36:57.645*:ksq.c@9841:ksqgtlctx(): ksqgtlctx: updated ksqlral, ksqlral:0x9e6b2370, res:0x9e7f0788
2022-09-02 11:36:57.645*:ksq.c@9851:ksqgtlctx(): ksqgtlctx: updated lock mode, mode:4 req:0
2022-09-02 11:36:57.645*:ksq.c@9960:ksqgtlctx(): SUCCESS
Checking v$lock_type we see that the OD lock is the “Online DDLs” lock, with the description “Lock to prevent concurrent online DDLs” and its first parameter is the object_id of the object that is the target of the DDL. The value in the trace file (000230A4) identifies the index that we are coalescing; at mode 4 the lock mode is fairly aggressive, but I’m surprised that it isn’t 6 – if we were to interpret the value the way we would for TM locks it would suggest that two sessions could coalesce the index at the same time!
Apart from 50 pairs of TT/HW locks (tablespace DDL / Segment Highwater mark) due to undo segments growing and shrinking, the rest of the ksq trace was taken up by 3,051 TX locks, typically reporting their acquisition and release on adjacent lines of the trace, e.g.:
2022-09-02 11:36:57.650*:ksq.c@9100:ksqgtlctx(): ksqtgtlctx: PDB mode
2022-09-02 11:36:57.650*:ksq.c@9175:ksqgtlctx(): *** TX-0004001C-00002F83-0039DED3-00000000 mode=6 flags=0x401 why=176 timeout=0 ***
2022-09-02 11:36:57.650*:ksq.c@9183:ksqgtlctx(): xcb=0x9bd37110, ktcdix=2147483647 topxcb=0x9bbeec68 ktcipt(topxcb)=0x0
2022-09-02 11:36:57.650*:ksq.c@9203:ksqgtlctx(): ksqgtlctx: Initializing lock structure
2022-09-02 11:36:57.650*:ksq.c@9324:ksqgtlctx(): DID DUMP START
2022-09-02 11:36:57.650*:ksq.c@9328:ksqgtlctx(): ksqlkdid: 0001-0029-0000013C
2022-09-02 11:36:57.650*:ksq.c@9333:ksqgtlctx(): tktcmydid: 0001-0029-0000013C
2022-09-02 11:36:57.650*:ksq.c@9337:ksqgtlctx(): tksusesdi: 0000-0000-00000000
2022-09-02 11:36:57.650*:ksq.c@9341:ksqgtlctx(): tksusetxn: 0001-0029-0000013C
2022-09-02 11:36:57.650*:ksq.c@9343:ksqgtlctx(): DID DUMP END
2022-09-02 11:36:57.650*:ksq.c@9517:ksqgtlctx(): ksqgtlctx: did not find link
2022-09-02 11:36:57.650*:ksq.c@9687:ksqgtlctx(): ksqgtlctx: updated ksqlrar1, ksqlrar:0x9e80b098, ksqlral:(nil)
2022-09-02 11:36:57.650*:ksq.c@9841:ksqgtlctx(): ksqgtlctx: updated ksqlral, ksqlral:0x9bd37148, res:0x9e80b098
2022-09-02 11:36:57.650*:ksq.c@9851:ksqgtlctx(): ksqgtlctx: updated lock mode, mode:6 req:0
2022-09-02 11:36:57.650*:ksq.c@9960:ksqgtlctx(): SUCCESS
2022-09-02 11:36:57.650*:ksq.c@10367:ksqrcli_int(): ksqrcli_int: updated ksqlral, ksqlral:0x9bd37148, res:0x9e80b098
2022-09-02 11:36:57.650*:ksq.c@10501:ksqrcli_int(): returns 0
Coalesce – Workload
We’ve examined the end result of a coalesce, and seen something of the mechanism that Oracle adopts to get to that result, but what does it cost (in terms of work done)? In many cases it’s sufficient to limit the analysis to:
- how much I/O
- how much CPU
- how much undo and redo generated
The obvious I/O comes from the requirement to walk the index in leaf block order, and the dbwr will eventually have to write back every block (including the empty ones). But that I/O, and the inevitable CPU usage is not particularly interesting, what’s more interesting (and more of a threat) is the impact of the undo and redo. This is where the snapsthos of session stats and redo stats give us the information we need to know, and all I’m going to look at are the redo-related stats for the test:
Name Value
---- -----
messages sent 92
calls to kcmgcs 81
calls to kcmgas 6,118
calls to get snapshot scn: kcmgss 3,075
redo entries 34,810
redo size 76,475,936
redo buffer allocation retries 39
redo subscn max counts 1,049
redo synch time 3
redo synch time (usec) 33,207
redo synch time overhead (usec) 159
redo synch time overhead count ( 2ms) 1
redo synch writes 1
redo write info find 1
undo change vector size 55,062,672
rollback changes - undo records applied 287
Bearing in mind that this index started at roughly 3,600 blocks / 28MB and coalesced to roughly 560 blocks / 4.5MB I want to draw your attention to just three of the figures (highlighted): the number and total size of redo records generated, and the volume of undo generated. 23,810 redo records, 75MB of redo, of which 55MB was due to undo.
It’s nice to see that the undo figure is consistent with the sum of the writes we saw in the snapshot of v$rollstat. But the numbers warn us that there’s a lot of work going into a coalesce – and it could have a big impact on other users.
My session is generating a lot of undo, and it’s cycling through every undo segment as it does so – that means other sessions that need to create read-consistent images of recently changed data blocks that are completely unrelated to my index may have to work backwards through a large number of undo blocks trying to find upper bound SCNs (check for statistics like: ‘transaction tables consistent read%’)
You’ll notice that I’ve also reported “rollback changes – undo records applied”; these are appearing because of “DML restarts” that make a statement roll back and try again the first time it triggers an undo segment extension. Luckily all my transactions are very small so each individual transaction won’t suffer much if it has to restart, but if you have a long running DML statement and I keep filling and extending undo segments (possibly shrinking other undo segments to do so) that’s going to increase your chances of finding your undo segment full and doing a huge rollback and restart of your statement. Be very careful about timing your coalesce commands.
Since I’ve dumped all the redo generated during the test run I’ll finish by showing a little analysis of the results. The trace file for this 28MB index was over 250MB so it’s not something you’d dump on a production size coalesce.
All I’m going to do is use grep to pull out the redo OP codes of every change vector in the file and show you a couple of extracts from the results. First a commonly occurring pattern:
CHANGE #1 CON_ID:3 TYP:2 CLS:1 AFN:36 DBA:0x090014d3 OBJ:143528 SCN:0x00000000024f686d SEQ:1 OP:4.1 ENC:0 RBL:0 FLG:0x0000
CHANGE #1 CON_ID:3 TYP:2 CLS:1 AFN:36 DBA:0x0900152e OBJ:143528 SCN:0x00000000024f686d SEQ:1 OP:4.1 ENC:0 RBL:0 FLG:0x0000
CHANGE #1 CON_ID:3 TYP:0 CLS:31 AFN:17 DBA:0x04402750 OBJ:4294967295 SCN:0x00000000024f685d SEQ:1 OP:5.2 ENC:0 RBL:0 FLG:0x0000
CHANGE #2 CON_ID:3 TYP:1 CLS:32 AFN:17 DBA:0x0440ec96 OBJ:4294967295 SCN:0x00000000024f686e SEQ:1 OP:5.1 ENC:0 RBL:0 FLG:0x0000
CHANGE #3 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x0900152e OBJ:143528 SCN:0x00000000024f686e SEQ:1 OP:10.6 ENC:0 RBL:0 FLG:0x0000
CHANGE #1 CON_ID:3 TYP:0 CLS:32 AFN:17 DBA:0x0440ec96 OBJ:4294967295 SCN:0x00000000024f686e SEQ:2 OP:5.1 ENC:0 RBL:0 FLG:0x0000
CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x090014d3 OBJ:143528 SCN:0x00000000024f686e SEQ:1 OP:10.6 ENC:0 RBL:0 FLG:0x0000
CHANGE #1 CON_ID:3 TYP:0 CLS:32 AFN:17 DBA:0x0440ec96 OBJ:4294967295 SCN:0x00000000024f686e SEQ:3 OP:5.1 ENC:0 RBL:0 FLG:0x0000
CHANGE #2 CON_ID:3 TYP:2 CLS:1 AFN:36 DBA:0x0900018a OBJ:143528 SCN:0x00000000024f67c1 SEQ:1 OP:10.11 ENC:0 RBL:0 FLG:0x0000
CHANGE #1 CON_ID:3 TYP:2 CLS:1 AFN:36 DBA:0x09000438 OBJ:143528 SCN:0x00000000024f686d SEQ:1 OP:4.1 ENC:0 RBL:0 FLG:0x0000
CHANGE #1 CON_ID:3 TYP:0 CLS:32 AFN:17 DBA:0x0440ec96 OBJ:4294967295 SCN:0x00000000024f686e SEQ:4 OP:5.1 ENC:0 RBL:0 FLG:0x0000
CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x09000438 OBJ:143528
SCN:0x00000000024f686e SEQ:1 OP:10.39 ENC:0 RBL:0 FLG:0x0000
CHANGE #1 CON_ID:3 TYP:0 CLS:31 AFN:17 DBA:0x04402750 OBJ:4294967295 SCN:0x00000000024f686e SEQ:1 OP:5.2 ENC:0 RBL:0 FLG:0x0000
CHANGE #2 CON_ID:3 TYP:1 CLS:32 AFN:17 DBA:0x0440ec97 OBJ:4294967295 SCN:0x00000000024f686e SEQ:1 OP:5.1 ENC:0 RBL:0 FLG:0x0000
CHANGE #3 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x090014d3 OBJ:143528 SCN:0x00000000024f686e SEQ:2 OP:10.8 ENC:0 RBL:0 FLG:0x0000
CHANGE #1 CON_ID:3 TYP:0 CLS:31 AFN:17 DBA:0x04402750 OBJ:4294967295 SCN:0x00000000024f686e SEQ:2 OP:5.2 ENC:0 RBL:0 FLG:0x0000
CHANGE #2 CON_ID:3 TYP:1 CLS:32 AFN:17 DBA:0x0440ec98 OBJ:4294967295 SCN:0x00000000024f686e SEQ:1 OP:5.1 ENC:0 RBL:0 FLG:0x0000
CHANGE #3 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x0900152e OBJ:143528 SCN:0x00000000024f686e SEQ:2 OP:10.34 ENC:0 RBL:0 FLG:0x0000
CHANGE #1 CON_ID:3 TYP:0 CLS:8 AFN:36 DBA:0x09001500 OBJ:143528 SCN:0x00000000024f685a SEQ:1 OP:13.22 ENC:0 RBL:0 FLG:0x0000
CHANGE #1 CON_ID:3 TYP:0 CLS:31 AFN:17 DBA:0x04402750 OBJ:4294967295 SCN:0x00000000024f686e SEQ:3 OP:5.4 ENC:0 RBL:0 FLG:0x0000
The last line is Op Code 5.4, a commit (or rollback), and I picked a batch of rows between one commit and the next, so this entire set of 20 change vectors is a single transaction taking place in the coalesce. I’ve placed gaps before every “Change #1” to show the boundaries between redo records. As you can see, my “common pattern” transaction is 11 redo records; that’s another sanity check: we saw roughly 3,000 TX enqueues, and 34,800 redo entries: 11 * 3,000 = 33,000, which is a good enough match.
Op Code 5.2 is “get next undo block”, Op Code 5.1 is “create undo record”, so I’m going to simplify the list by removing those codes. Removing some of the irrelevant material from the start and end of each line the example reduces to:
DBA:0x090014d3 OBJ:143528 SCN:0x00000000024f686d SEQ:1 OP:4.1
DBA:0x0900152e OBJ:143528 SCN:0x00000000024f686d SEQ:1 OP:4.1
DBA:0x0900152e OBJ:143528 SCN:0x00000000024f686e SEQ:1 OP:10.6
DBA:0x090014d3 OBJ:143528 SCN:0x00000000024f686e SEQ:1 OP:10.6
DBA:0x0900018a OBJ:143528 SCN:0x00000000024f67c1 SEQ:1 OP:10.11
DBA:0x09000438 OBJ:143528 SCN:0x00000000024f686d SEQ:1 OP:4.1
DBA:0x09000438 OBJ:143528 SCN:0x00000000024f686e SEQ:1 OP:10.39
DBA:0x090014d3 OBJ:143528 SCN:0x00000000024f686e SEQ:2 OP:10.8
DBA:0x0900152e OBJ:143528 SCN:0x00000000024f686e SEQ:2 OP:10.34
DBA:0x09001500 OBJ:143528 SCN:0x00000000024f685a SEQ:1 OP:13.22
Translating the OP Codes (and adding in a little information I have about which blocks the block addresses (DBA) correspond to) this is what the transaction does
- block cleanout of leaf block 0x090014d3 (4.1)
- block cleanout of leaf block 0x0900152e (4.1)
- lock leaf block 0x0900152e (10.6)
- lock leaf block 0x090014d3 (10.6)
- change the “pointer to previous” of leaf block 0x0900018a (10.11)
- block cleanout of branch block 0x09000438 (4.1)
- update branch block 0x09000438, delete one leaf entry (10.39)
- create new version of leaf block 0x090014d3 (10.8)
- create empty version of leaf block 0x0900152e (10.34)
- update space management level 1 bitmap block (13.22)
So where does the huge amount of redo appear. If we looked at the 11 Redo Record Headers for the extract we could use the LEN information to point us to the cirtical bits:
REDO RECORD - Thread:1 RBA: 0x000391.000174dc.01c0 LEN: 0x0058 VLD: 0x01 CON_UID: 3792595
REDO RECORD - Thread:1 RBA: 0x000391.000174dd.0028 LEN: 0x0060 VLD: 0x01 CON_UID: 3792595
REDO RECORD - Thread:1 RBA: 0x000391.000174dd.0088 LEN: 0x0164 VLD: 0x01 CON_UID: 3792595
REDO RECORD - Thread:1 RBA: 0x000391.000174de.0010 LEN: 0x00e4 VLD: 0x01 CON_UID: 3792595
REDO RECORD - Thread:1 RBA: 0x000391.000174de.00f4 LEN: 0x00ec VLD: 0x01 CON_UID: 3792595
REDO RECORD - Thread:1 RBA: 0x000391.000174de.01e0 LEN: 0x0058 VLD: 0x01 CON_UID: 3792595
REDO RECORD - Thread:1 RBA: 0x000391.000174df.0048 LEN: 0x0104 VLD: 0x01 CON_UID: 3792595
REDO RECORD - Thread:1 RBA: 0x000391.000174df.014c LEN: 0x3a88 VLD: 0x01 CON_UID: 3792595
REDO RECORD - Thread:1 RBA: 0x000391.000174fd.01b4 LEN: 0x20bc VLD: 0x01 CON_UID: 3792595
REDO RECORD - Thread:1 RBA: 0x000391.0001750e.0180 LEN: 0x0064 VLD: 0x01 CON_UID: 3792595
REDO RECORD - Thread:1 RBA: 0x000391.0001750e.01e4 LEN: 0x0058 VLD: 0x01 CON_UID: 3792595
I’ve highlighted the two big ones – records 8 and 9, which are the ones holding the 10.8 (create new leaf) and 10.34 (make block empty). Why are they so big at 14,984 bytes and 8,380 bytes respectively?
Record 8 includes a change vector (5.1) for the undo of the replaced block which is a block image at 8,032 bytes, and a change vector for the new version of the block in a format similar to an array insert which happened to have 344 rows at this point for a size of roughly 6,500 bytes.
Record 9 includes a change vector (5.1) for the undo of the emptied block, again a block image of 8,032 bytes. But the 10.34 itself is only a few tens of bytes.
This test highlights a particularly nasty threat from coalesce and its “pairwise” clean-up. Checking the “post-delete” tree dump I can see I’ve emptied leaf block 0x0900152e by copying 30 rows back into leaf block 0x090014d3, and I can see that this is the fifth leaf block that I’ve emptied into 0x090014d3, and I can see that I’ll be doing one more pass to get that block full; and each time I do this I dump two block images, and an “array-update” redo change vector that gets bigger and bigger on each pass until it’s nearly the full 8KB. The operation generates a lot of undo and a lot of redo.
Coalesce – concurrency
As a quick test of what happens when other work is going on on the table I ran a little script to insert an extra 100 rows (without committing) into the table just after the big delete but just before the coalesce, generating random values from the same range as the original values.
The coalesce didn’t seem to take any extra time and I didn’t see any enqueue waits or buffer busy waits (though a different test of 3,000 rapid single row inserts with commits while the coalesce was running manage to get one buffer busy wait on a branch block).
The final result, though was not very good. With 100 uncommitted inserts getting in the way the index report 687 “full” blocks rather than the 553 that we saw originally. That’s an increase of more than one block per row inserted.
Basically when Oracle hits a block with an uncommitted change it looks as if it says – “I can’t copy those rows backwards so I’ll have to leave the current block wherever I’ve got to, skip the modified block and restart the coalesce in the next block along” So every block with an uncommitted change could result in two extra blocks ultimately not being packed as well as they could be.
Click here if you want to see the full treedump
----- begin tree dump
branch: 0x9000104 150995204 (0: nrow: 8, level: 2)
branch: 0x9000438 150996024 (-1: nrow: 78, level: 1)
leaf: 0x900016d 150995309 (-1: row:377.377 avs:833)
leaf: 0x90014d3 151000275 (0: row:377.377 avs:833)
leaf: 0x900118c 150999436 (1: row:377.377 avs:833)
leaf: 0x9000370 150995824 (2: row:377.377 avs:833)
leaf: 0x900011e 150995230 (3: row:120.120 avs:5716)
leaf: 0x9000a0e 150997518 (4: row:49.49 avs:7065)
leaf: 0x9001258 150999640 (5: row:377.377 avs:833)
leaf: 0x9000658 150996568 (6: row:377.377 avs:833)
leaf: 0x9000b8b 150997899 (7: row:377.377 avs:833)
leaf: 0x9000155 150995285 (8: row:377.377 avs:833)
leaf: 0x9000ba1 150997921 (9: row:377.377 avs:833)
leaf: 0x900063c 150996540 (10: row:377.377 avs:833)
leaf: 0x9000d3b 150998331 (11: row:377.377 avs:833)
leaf: 0x9000469 150996073 (12: row:114.114 avs:5830)
leaf: 0x9000bfb 150998011 (13: row:51.51 avs:7027)
leaf: 0x900155d 151000413 (14: row:377.377 avs:833)
leaf: 0x9000ba2 150997922 (15: row:377.377 avs:833)
leaf: 0x9001512 151000338 (16: row:377.377 avs:833)
leaf: 0x9000d74 150998388 (17: row:377.377 avs:833)
leaf: 0x90005be 150996414 (18: row:377.377 avs:833)
leaf: 0x90005b4 150996404 (19: row:377.377 avs:833)
leaf: 0x9000c24 150998052 (20: row:377.377 avs:833)
leaf: 0x90001a7 150995367 (21: row:377.377 avs:833)
leaf: 0x9001563 151000419 (22: row:377.377 avs:833)
leaf: 0x9000a68 150997608 (23: row:377.377 avs:833)
leaf: 0x90011a7 150999463 (24: row:377.377 avs:833)
leaf: 0x90001b9 150995385 (25: row:327.327 avs:1783)
leaf: 0x9000ab6 150997686 (26: row:52.52 avs:7008)
leaf: 0x900149f 151000223 (27: row:377.377 avs:833)
leaf: 0x900123d 150999613 (28: row:328.328 avs:1764)
leaf: 0x900033c 150995772 (29: row:89.89 avs:6305)
leaf: 0x9000b9d 150997917 (30: row:45.45 avs:7141)
leaf: 0x90014ad 151000237 (31: row:377.377 avs:833)
leaf: 0x9000d40 150998336 (32: row:377.377 avs:833)
leaf: 0x9000166 150995302 (33: row:377.377 avs:833)
leaf: 0x9000c70 150998128 (34: row:377.377 avs:833)
leaf: 0x90014e9 151000297 (35: row:377.377 avs:833)
leaf: 0x9000d32 150998322 (36: row:377.377 avs:833)
leaf: 0x9001546 151000390 (37: row:377.377 avs:833)
leaf: 0x900018b 150995339 (38: row:377.377 avs:833)
leaf: 0x9000b8a 150997898 (39: row:377.377 avs:833)
leaf: 0x9000c4c 150998092 (40: row:169.169 avs:4785)
leaf: 0x9000a89 150997641 (41: row:69.69 avs:6685)
leaf: 0x9000335 150995765 (42: row:306.306 avs:2182)
leaf: 0x9000196 150995350 (43: row:51.51 avs:7027)
leaf: 0x900134d 150999885 (44: row:377.377 avs:833)
leaf: 0x90005a7 150996391 (45: row:243.243 avs:3379)
leaf: 0x9000116 150995222 (46: row:54.54 avs:6970)
leaf: 0x900130b 150999819 (47: row:377.377 avs:833)
leaf: 0x9000604 150996484 (48: row:377.377 avs:833)
leaf: 0x9000655 150996565 (49: row:377.377 avs:833)
leaf: 0x9000d7d 150998397 (50: row:185.185 avs:4481)
leaf: 0x9000958 150997336 (51: row:53.53 avs:6989)
leaf: 0x90011aa 150999466 (52: row:377.377 avs:833)
leaf: 0x900102a 150999082 (53: row:377.377 avs:833)
leaf: 0x9000a6d 150997613 (54: row:377.377 avs:833)
leaf: 0x90014f8 151000312 (55: row:377.377 avs:833)
leaf: 0x900135d 150999901 (56: row:344.344 avs:1460)
leaf: 0x9000a37 150997559 (57: row:45.45 avs:7141)
leaf: 0x900122d 150999597 (58: row:341.341 avs:1517)
leaf: 0x9000afe 150997758 (59: row:51.51 avs:7027)
leaf: 0x9001536 151000374 (60: row:377.377 avs:833)
leaf: 0x9000644 150996548 (61: row:113.113 avs:5849)
leaf: 0x9000c69 150998121 (62: row:75.75 avs:6571)
leaf: 0x9000141 150995265 (63: row:377.377 avs:833)
leaf: 0x9000c56 150998102 (64: row:377.377 avs:833)
leaf: 0x900059d 150996381 (65: row:377.377 avs:833)
leaf: 0x9000c46 150998086 (66: row:377.377 avs:833)
leaf: 0x9000af0 150997744 (67: row:377.377 avs:833)
leaf: 0x90001bd 150995389 (68: row:377.377 avs:833)
leaf: 0x9000baa 150997930 (69: row:377.377 avs:833)
leaf: 0x9000c4f 150998095 (70: row:377.377 avs:833)
leaf: 0x9000639 150996537 (71: row:377.377 avs:833)
leaf: 0x9000c1f 150998047 (72: row:377.377 avs:833)
leaf: 0x9000d4a 150998346 (73: row:377.377 avs:833)
leaf: 0x900153d 151000381 (74: row:377.377 avs:833)
leaf: 0x9000e74 150998644 (75: row:377.377 avs:833)
leaf: 0x9000d2a 150998314 (76: row:244.244 avs:3360)
branch: 0x9000e45 150998597 (0: nrow: 75, level: 1)
leaf: 0x900047a 150996090 (-1: row:377.377 avs:833)
leaf: 0x9000725 150996773 (0: row:377.377 avs:833)
leaf: 0x90001e2 150995426 (1: row:377.377 avs:833)
leaf: 0x9000e43 150998595 (2: row:156.156 avs:5032)
leaf: 0x9000e32 150998578 (3: row:61.61 avs:6837)
leaf: 0x9000258 150995544 (4: row:377.377 avs:833)
leaf: 0x90007dd 150996957 (5: row:377.377 avs:833)
leaf: 0x900166e 151000686 (6: row:377.377 avs:833)
leaf: 0x90001aa 150995370 (7: row:377.377 avs:833)
leaf: 0x9000c44 150998084 (8: row:377.377 avs:833)
leaf: 0x90014e8 151000296 (9: row:71.71 avs:6647)
leaf: 0x900067a 150996602 (10: row:66.66 avs:6742)
leaf: 0x9000ba9 150997929 (11: row:71.71 avs:6647)
leaf: 0x900033f 150995775 (12: row:80.80 avs:6476)
leaf: 0x9000aeb 150997739 (13: row:377.377 avs:833)
leaf: 0x90013e7 151000039 (14: row:377.377 avs:833)
leaf: 0x900067b 150996603 (15: row:377.377 avs:833)
leaf: 0x9000bff 150998015 (16: row:377.377 avs:833)
leaf: 0x90001b5 150995381 (17: row:377.377 avs:833)
leaf: 0x9000364 150995812 (18: row:167.167 avs:4823)
leaf: 0x9001550 151000400 (19: row:42.42 avs:7198)
leaf: 0x90005e1 150996449 (20: row:377.377 avs:833)
leaf: 0x9000c37 150998071 (21: row:293.293 avs:2429)
leaf: 0x900065d 150996573 (22: row:92.92 avs:6248)
leaf: 0x9000c2d 150998061 (23: row:377.377 avs:833)
leaf: 0x9000374 150995828 (24: row:377.377 avs:833)
leaf: 0x900148f 151000207 (25: row:377.377 avs:833)
leaf: 0x9000e63 150998627 (26: row:377.377 avs:833)
leaf: 0x9000eb1 150998705 (27: row:377.377 avs:833)
leaf: 0x9000c30 150998064 (28: row:377.377 avs:833)
leaf: 0x9000612 150996498 (29: row:256.256 avs:3132)
leaf: 0x9000c08 150998024 (30: row:68.68 avs:6704)
leaf: 0x900074e 150996814 (31: row:377.377 avs:833)
leaf: 0x9000132 150995250 (32: row:305.305 avs:2201)
leaf: 0x9000473 150996083 (33: row:73.73 avs:6609)
leaf: 0x9000d0a 150998282 (34: row:68.68 avs:6704)
leaf: 0x9000755 150996821 (35: row:377.377 avs:833)
leaf: 0x9000419 150995993 (36: row:377.377 avs:833)
leaf: 0x9000eeb 150998763 (37: row:377.377 avs:833)
leaf: 0x9000d04 150998276 (38: row:293.293 avs:2429)
leaf: 0x9000d62 150998370 (39: row:83.83 avs:6419)
leaf: 0x9000767 150996839 (40: row:377.377 avs:833)
leaf: 0x9000323 150995747 (41: row:377.377 avs:833)
leaf: 0x9000c1e 150998046 (42: row:282.282 avs:2638)
leaf: 0x9000d5b 150998363 (43: row:58.58 avs:6894)
leaf: 0x900060f 150996495 (44: row:76.76 avs:6552)
leaf: 0x9000d5a 150998362 (45: row:65.65 avs:6761)
leaf: 0x90001f1 150995441 (46: row:377.377 avs:833)
leaf: 0x9000c7e 150998142 (47: row:377.377 avs:833)
leaf: 0x900061c 150996508 (48: row:377.377 avs:833)
leaf: 0x9000159 150995289 (49: row:149.149 avs:5165)
leaf: 0x9000c5b 150998107 (50: row:73.73 avs:6609)
leaf: 0x9000605 150996485 (51: row:377.377 avs:833)
leaf: 0x9000a97 150997655 (52: row:377.377 avs:833)
leaf: 0x9000b9a 150997914 (53: row:370.370 avs:966)
leaf: 0x9000c0c 150998028 (54: row:61.61 avs:6837)
leaf: 0x90001fd 150995453 (55: row:377.377 avs:833)
leaf: 0x900075d 150996829 (56: row:377.377 avs:833)
leaf: 0x9001078 150999160 (57: row:377.377 avs:833)
leaf: 0x9001193 150999443 (58: row:377.377 avs:833)
leaf: 0x9001334 150999860 (59: row:377.377 avs:833)
leaf: 0x9000947 150997319 (60: row:377.377 avs:833)
leaf: 0x9000a98 150997656 (61: row:377.377 avs:833)
leaf: 0x90008cb 150997195 (62: row:377.377 avs:833)
leaf: 0x9001020 150999072 (63: row:377.377 avs:833)
leaf: 0x90001d0 150995408 (64: row:377.377 avs:833)
leaf: 0x9000221 150995489 (65: row:377.377 avs:833)
leaf: 0x9000158 150995288 (66: row:377.377 avs:833)
leaf: 0x900035f 150995807 (67: row:377.377 avs:833)
leaf: 0x900103a 150999098 (68: row:377.377 avs:833)
leaf: 0x900156e 151000430 (69: row:377.377 avs:833)
leaf: 0x9000129 150995241 (70: row:377.377 avs:833)
leaf: 0x9000349 150995785 (71: row:377.377 avs:833)
leaf: 0x90014bc 151000252 (72: row:377.377 avs:833)
leaf: 0x90011ac 150999468 (73: row:329.329 avs:1745)
branch: 0x90007d1 150996945 (1: nrow: 75, level: 1)
leaf: 0x900017a 150995322 (-1: row:64.64 avs:6780)
leaf: 0x9000d6f 150998383 (0: row:202.202 avs:4158)
leaf: 0x9000472 150996082 (1: row:76.76 avs:6552)
leaf: 0x9000e50 150998608 (2: row:377.377 avs:833)
leaf: 0x9000c0d 150998029 (3: row:266.266 avs:2942)
leaf: 0x9000757 150996823 (4: row:79.79 avs:6495)
leaf: 0x9000d54 150998356 (5: row:377.377 avs:833)
leaf: 0x9000c17 150998039 (6: row:377.377 avs:833)
leaf: 0x9000710 150996752 (7: row:377.377 avs:833)
leaf: 0x9000107 150995207 (8: row:377.377 avs:833)
leaf: 0x9000d4d 150998349 (9: row:142.142 avs:5298)
leaf: 0x9000fdf 150999007 (10: row:48.48 avs:7084)
leaf: 0x9000250 150995536 (11: row:377.377 avs:833)
leaf: 0x900125d 150999645 (12: row:304.304 avs:2220)
leaf: 0x9000431 150996017 (13: row:56.56 avs:6932)
leaf: 0x9000fda 150999002 (14: row:377.377 avs:833)
leaf: 0x900047f 150996095 (15: row:377.377 avs:833)
leaf: 0x90008fb 150997243 (16: row:377.377 avs:833)
leaf: 0x9000e36 150998582 (17: row:377.377 avs:833)
leaf: 0x9000e09 150998537 (18: row:377.377 avs:833)
leaf: 0x90013d9 151000025 (19: row:377.377 avs:833)
leaf: 0x90008a8 150997160 (20: row:377.377 avs:833)
leaf: 0x9000fc1 150998977 (21: row:377.377 avs:833)
leaf: 0x9000435 150996021 (22: row:377.377 avs:833)
leaf: 0x90008d3 150997203 (23: row:377.377 avs:833)
leaf: 0x9000d2d 150998317 (24: row:377.377 avs:833)
leaf: 0x9000d1f 150998303 (25: row:377.377 avs:833)
leaf: 0x9000ecc 150998732 (26: row:377.377 avs:833)
leaf: 0x9000eee 150998766 (27: row:377.377 avs:833)
leaf: 0x90001f9 150995449 (28: row:377.377 avs:833)
leaf: 0x9000744 150996804 (29: row:377.377 avs:833)
leaf: 0x900044e 150996046 (30: row:377.377 avs:833)
leaf: 0x9000136 150995254 (31: row:377.377 avs:833)
leaf: 0x90007ce 150996942 (32: row:377.377 avs:833)
leaf: 0x9000476 150996086 (33: row:377.377 avs:833)
leaf: 0x9000bd0 150997968 (34: row:377.377 avs:833)
leaf: 0x9000776 150996854 (35: row:377.377 avs:833)
leaf: 0x9000e76 150998646 (36: row:377.377 avs:833)
leaf: 0x9000173 150995315 (37: row:377.377 avs:833)
leaf: 0x9000e15 150998549 (38: row:110.110 avs:5906)
leaf: 0x9000245 150995525 (39: row:59.59 avs:6875)
leaf: 0x900102d 150999085 (40: row:377.377 avs:833)
leaf: 0x90001f3 150995443 (41: row:377.377 avs:833)
leaf: 0x900034a 150995786 (42: row:377.377 avs:833)
leaf: 0x9000ede 150998750 (43: row:377.377 avs:833)
leaf: 0x900024d 150995533 (44: row:377.377 avs:833)
leaf: 0x90007e2 150996962 (45: row:377.377 avs:833)
leaf: 0x9000450 150996048 (46: row:377.377 avs:833)
leaf: 0x900078a 150996874 (47: row:377.377 avs:833)
leaf: 0x9000e1d 150998557 (48: row:377.377 avs:833)
leaf: 0x9000e39 150998585 (49: row:377.377 avs:833)
leaf: 0x9000e19 150998553 (50: row:377.377 avs:833)
leaf: 0x9000779 150996857 (51: row:377.377 avs:833)
leaf: 0x9000c21 150998049 (52: row:377.377 avs:833)
leaf: 0x9000d5d 150998365 (53: row:377.377 avs:833)
leaf: 0x90004e0 150996192 (54: row:377.377 avs:833)
leaf: 0x9000498 150996120 (55: row:377.377 avs:833)
leaf: 0x9000ffe 150999038 (56: row:377.377 avs:833)
leaf: 0x9000975 150997365 (57: row:377.377 avs:833)
leaf: 0x90011d5 150999509 (58: row:274.274 avs:2790)
leaf: 0x9000a52 150997586 (59: row:55.55 avs:6951)
leaf: 0x9001347 150999879 (60: row:143.143 avs:5279)
leaf: 0x900097b 150997371 (61: row:66.66 avs:6742)
leaf: 0x9001129 150999337 (62: row:357.357 avs:1213)
leaf: 0x90008ad 150997165 (63: row:55.55 avs:6951)
leaf: 0x9001047 150999111 (64: row:42.42 avs:7198)
leaf: 0x90004b3 150996147 (65: row:360.360 avs:1156)
leaf: 0x9001126 150999334 (66: row:50.50 avs:7046)
leaf: 0x90004d5 150996181 (67: row:59.59 avs:6875)
leaf: 0x900114f 150999375 (68: row:377.377 avs:833)
leaf: 0x9000ff6 150999030 (69: row:377.377 avs:833)
leaf: 0x9000ead 150998701 (70: row:317.317 avs:1973)
leaf: 0x90007cc 150996940 (71: row:55.55 avs:6951)
leaf: 0x9000eea 150998762 (72: row:377.377 avs:833)
leaf: 0x900097f 150997375 (73: row:346.346 avs:1422)
branch: 0x9000e8a 150998666 (2: nrow: 78, level: 1)
leaf: 0x9000142 150995266 (-1: row:60.60 avs:6856)
leaf: 0x90014c1 151000257 (0: row:377.377 avs:833)
leaf: 0x9001398 150999960 (1: row:377.377 avs:833)
leaf: 0x900110d 150999309 (2: row:377.377 avs:833)
leaf: 0x9000372 150995826 (3: row:377.377 avs:833)
leaf: 0x9001136 150999350 (4: row:377.377 avs:833)
leaf: 0x9000940 150997312 (5: row:367.367 avs:1023)
leaf: 0x9000bfe 150998014 (6: row:84.84 avs:6400)
leaf: 0x90001d1 150995409 (7: row:377.377 avs:833)
leaf: 0x900112d 150999341 (8: row:377.377 avs:833)
leaf: 0x9000931 150997297 (9: row:102.102 avs:6058)
leaf: 0x9001135 150999349 (10: row:56.56 avs:6932)
leaf: 0x9000170 150995312 (11: row:118.118 avs:5754)
leaf: 0x90008b5 150997173 (12: row:51.51 avs:7027)
leaf: 0x90013e2 151000034 (13: row:377.377 avs:833)
leaf: 0x9001194 150999444 (14: row:377.377 avs:833)
leaf: 0x9000ee5 150998757 (15: row:377.377 avs:833)
leaf: 0x9000976 150997366 (16: row:171.171 avs:4747)
leaf: 0x9001238 150999608 (17: row:57.57 avs:6913)
leaf: 0x900093d 150997309 (18: row:377.377 avs:833)
leaf: 0x9000a32 150997554 (19: row:377.377 avs:833)
leaf: 0x90001ad 150995373 (20: row:377.377 avs:833)
leaf: 0x9001547 151000391 (21: row:377.377 avs:833)
leaf: 0x9000ae3 150997731 (22: row:377.377 avs:833)
leaf: 0x9000656 150996566 (23: row:377.377 avs:833)
leaf: 0x900138a 150999946 (24: row:377.377 avs:833)
leaf: 0x90005b8 150996408 (25: row:377.377 avs:833)
leaf: 0x900126e 150999662 (26: row:377.377 avs:833)
leaf: 0x9000c74 150998132 (27: row:377.377 avs:833)
leaf: 0x9000318 150995736 (28: row:377.377 avs:833)
leaf: 0x9000160 150995296 (29: row:377.377 avs:833)
leaf: 0x9001278 150999672 (30: row:377.377 avs:833)
leaf: 0x90008f3 150997235 (31: row:375.375 avs:871)
leaf: 0x900101c 150999068 (32: row:47.47 avs:7103)
leaf: 0x9000921 150997281 (33: row:52.52 avs:7008)
leaf: 0x9001123 150999331 (34: row:377.377 avs:833)
leaf: 0x9000138 150995256 (35: row:377.377 avs:833)
leaf: 0x9000345 150995781 (36: row:377.377 avs:833)
leaf: 0x90001a4 150995364 (37: row:377.377 avs:833)
leaf: 0x9000304 150995716 (38: row:377.377 avs:833)
leaf: 0x900125a 150999642 (39: row:377.377 avs:833)
leaf: 0x90014ff 151000319 (40: row:377.377 avs:833)
leaf: 0x9000fa5 150998949 (41: row:377.377 avs:833)
leaf: 0x9000f9a 150998938 (42: row:377.377 avs:833)
leaf: 0x900091e 150997278 (43: row:377.377 avs:833)
leaf: 0x9001153 150999379 (44: row:377.377 avs:833)
leaf: 0x90004c1 150996161 (45: row:377.377 avs:833)
leaf: 0x9000fc2 150998978 (46: row:335.335 avs:1631)
leaf: 0x9000220 150995488 (47: row:69.69 avs:6685)
leaf: 0x9000fd8 150999000 (48: row:377.377 avs:833)
leaf: 0x9000168 150995304 (49: row:377.377 avs:833)
leaf: 0x9001105 150999301 (50: row:377.377 avs:833)
leaf: 0x9001368 150999912 (51: row:377.377 avs:833)
leaf: 0x9000358 150995800 (52: row:377.377 avs:833)
leaf: 0x9001652 151000658 (53: row:82.82 avs:6438)
leaf: 0x9000125 150995237 (54: row:45.45 avs:7141)
leaf: 0x90014a9 151000233 (55: row:377.377 avs:833)
leaf: 0x9000bfa 150998010 (56: row:377.377 avs:833)
leaf: 0x9000bd7 150997975 (57: row:377.377 avs:833)
leaf: 0x9000ad6 150997718 (58: row:377.377 avs:833)
leaf: 0x9000884 150997124 (59: row:377.377 avs:833)
leaf: 0x9000fcc 150998988 (60: row:377.377 avs:833)
leaf: 0x90011da 150999514 (61: row:377.377 avs:833)
leaf: 0x90008eb 150997227 (62: row:377.377 avs:833)
leaf: 0x9001391 150999953 (63: row:377.377 avs:833)
leaf: 0x9001104 150999300 (64: row:377.377 avs:833)
leaf: 0x900043a 150996026 (65: row:377.377 avs:833)
leaf: 0x9000ebf 150998719 (66: row:215.215 avs:3911)
leaf: 0x90007cf 150996943 (67: row:68.68 avs:6704)
leaf: 0x9000e83 150998659 (68: row:377.377 avs:833)
leaf: 0x90007af 150996911 (69: row:377.377 avs:833)
leaf: 0x900127a 150999674 (70: row:377.377 avs:833)
leaf: 0x900166d 151000685 (71: row:377.377 avs:833)
leaf: 0x90014c9 151000265 (72: row:377.377 avs:833)
leaf: 0x9000bb4 150997940 (73: row:377.377 avs:833)
leaf: 0x9000616 150996502 (74: row:377.377 avs:833)
leaf: 0x90004ff 150996223 (75: row:377.377 avs:833)
leaf: 0x9001337 150999863 (76: row:283.283 avs:2619)
branch: 0x900043c 150996028 (3: nrow: 85, level: 1)
leaf: 0x9000171 150995313 (-1: row:377.377 avs:833)
leaf: 0x900120f 150999567 (0: row:351.351 avs:1327)
leaf: 0x9000424 150996004 (1: row:47.47 avs:7103)
leaf: 0x9000ebc 150998716 (2: row:52.52 avs:7008)
leaf: 0x9000791 150996881 (3: row:326.326 avs:1802)
leaf: 0x9000439 150996025 (4: row:71.71 avs:6647)
leaf: 0x9000e0c 150998540 (5: row:55.55 avs:6951)
leaf: 0x90007c8 150996936 (6: row:377.377 avs:833)
leaf: 0x90008b1 150997169 (7: row:377.377 avs:833)
leaf: 0x9000445 150996037 (8: row:377.377 avs:833)
leaf: 0x9000777 150996855 (9: row:377.377 avs:833)
leaf: 0x90001d7 150995415 (10: row:377.377 avs:833)
leaf: 0x90013ee 151000046 (11: row:377.377 avs:833)
leaf: 0x900134f 150999887 (12: row:377.377 avs:833)
leaf: 0x9000e68 150998632 (13: row:377.377 avs:833)
leaf: 0x9000f91 150998929 (14: row:377.377 avs:833)
leaf: 0x9001112 150999314 (15: row:317.317 avs:1973)
leaf: 0x900023f 150995519 (16: row:62.62 avs:6818)
leaf: 0x9000e85 150998661 (17: row:203.203 avs:4139)
leaf: 0x90004f3 150996211 (18: row:61.61 avs:6837)
leaf: 0x9000ee9 150998761 (19: row:377.377 avs:833)
leaf: 0x900041a 150995994 (20: row:377.377 avs:833)
leaf: 0x9000724 150996772 (21: row:124.124 avs:5640)
leaf: 0x9000418 150995992 (22: row:59.59 avs:6875)
leaf: 0x9000ebe 150998718 (23: row:377.377 avs:833)
leaf: 0x9000d5f 150998367 (24: row:98.98 avs:6134)
leaf: 0x9000460 150996064 (25: row:75.75 avs:6571)
leaf: 0x9000c54 150998100 (26: row:377.377 avs:833)
leaf: 0x9000f94 150998932 (27: row:377.377 avs:833)
leaf: 0x9000d36 150998326 (28: row:377.377 avs:833)
leaf: 0x9000e84 150998660 (29: row:377.377 avs:833)
leaf: 0x9000ee6 150998758 (30: row:377.377 avs:833)
leaf: 0x900042e 150996014 (31: row:377.377 avs:833)
leaf: 0x900073a 150996794 (32: row:377.377 avs:833)
leaf: 0x90011bc 150999484 (33: row:377.377 avs:833)
leaf: 0x900020d 150995469 (34: row:377.377 avs:833)
leaf: 0x9001356 150999894 (35: row:377.377 avs:833)
leaf: 0x9000e8e 150998670 (36: row:377.377 avs:833)
leaf: 0x900059c 150996380 (37: row:377.377 avs:833)
leaf: 0x90004de 150996190 (38: row:377.377 avs:833)
leaf: 0x9000fed 150999021 (39: row:377.377 avs:833)
leaf: 0x9000ff7 150999031 (40: row:377.377 avs:833)
leaf: 0x9000237 150995511 (41: row:377.377 avs:833)
leaf: 0x9000f8b 150998923 (42: row:318.318 avs:1954)
leaf: 0x9000494 150996116 (43: row:48.48 avs:7084)
leaf: 0x90011bf 150999487 (44: row:377.377 avs:833)
leaf: 0x9001249 150999625 (45: row:128.128 avs:5564)
leaf: 0x900104b 150999115 (46: row:60.60 avs:6856)
leaf: 0x90001e3 150995427 (47: row:207.207 avs:4063)
leaf: 0x9000c18 150998040 (48: row:63.63 avs:6799)
leaf: 0x900043b 150996027 (49: row:377.377 avs:833)
leaf: 0x90011de 150999518 (50: row:377.377 avs:833)
leaf: 0x90007f6 150996982 (51: row:377.377 avs:833)
leaf: 0x900027c 150995580 (52: row:377.377 avs:833)
leaf: 0x90001db 150995419 (53: row:377.377 avs:833)
leaf: 0x9000959 150997337 (54: row:346.346 avs:1422)
leaf: 0x9000417 150995991 (55: row:50.50 avs:7046)
leaf: 0x9001350 150999888 (56: row:377.377 avs:833)
leaf: 0x90004b6 150996150 (57: row:377.377 avs:833)
leaf: 0x900048e 150996110 (58: row:377.377 avs:833)
leaf: 0x900049f 150996127 (59: row:377.377 avs:833)
leaf: 0x90004d8 150996184 (60: row:377.377 avs:833)
leaf: 0x9000d09 150998281 (61: row:377.377 avs:833)
leaf: 0x9000ee8 150998760 (62: row:377.377 avs:833)
leaf: 0x900116c 150999404 (63: row:377.377 avs:833)
leaf: 0x9000ef0 150998768 (64: row:377.377 avs:833)
leaf: 0x9000e6c 150998636 (65: row:377.377 avs:833)
leaf: 0x9000e1b 150998555 (66: row:377.377 avs:833)
leaf: 0x900079f 150996895 (67: row:377.377 avs:833)
leaf: 0x900042d 150996013 (68: row:377.377 avs:833)
leaf: 0x90007b7 150996919 (69: row:377.377 avs:833)
leaf: 0x900103b 150999099 (70: row:377.377 avs:833)
leaf: 0x900017e 150995326 (71: row:377.377 avs:833)
leaf: 0x9000978 150997368 (72: row:377.377 avs:833)
leaf: 0x9001029 150999081 (73: row:302.302 avs:2258)
leaf: 0x90007f1 150996977 (74: row:68.68 avs:6704)
leaf: 0x9000e10 150998544 (75: row:377.377 avs:833)
leaf: 0x90007d7 150996951 (76: row:377.377 avs:833)
leaf: 0x9000117 150995223 (77: row:377.377 avs:833)
leaf: 0x900072f 150996783 (78: row:377.377 avs:833)
leaf: 0x9000415 150995989 (79: row:245.245 avs:3341)
leaf: 0x90001f6 150995446 (80: row:51.51 avs:7027)
leaf: 0x9000e25 150998565 (81: row:377.377 avs:833)
leaf: 0x900026b 150995563 (82: row:377.377 avs:833)
leaf: 0x900072b 150996779 (83: row:182.182 avs:4538)
branch: 0x9000e18 150998552 (4: nrow: 90, level: 1)
leaf: 0x900017b 150995323 (-1: row:361.361 avs:1137)
leaf: 0x90007fc 150996988 (0: row:57.57 avs:6913)
leaf: 0x9000fb2 150998962 (1: row:67.67 avs:6723)
leaf: 0x9000272 150995570 (2: row:377.377 avs:833)
leaf: 0x900075a 150996826 (3: row:135.135 avs:5431)
leaf: 0x90001d2 150995410 (4: row:87.87 avs:6343)
leaf: 0x9000c6c 150998124 (5: row:193.193 avs:4329)
leaf: 0x9000327 150995751 (6: row:93.93 avs:6229)
leaf: 0x9000bb5 150997941 (7: row:377.377 avs:833)
leaf: 0x900063e 150996542 (8: row:226.226 avs:3702)
leaf: 0x9000a93 150997651 (9: row:44.44 avs:7160)
leaf: 0x90014be 151000254 (10: row:377.377 avs:833)
leaf: 0x9000e2e 150998574 (11: row:377.377 avs:833)
leaf: 0x9001074 150999156 (12: row:224.224 avs:3740)
leaf: 0x9000eb6 150998710 (13: row:51.51 avs:7027)
leaf: 0x9000788 150996872 (14: row:377.377 avs:833)
leaf: 0x9000428 150996008 (15: row:118.118 avs:5754)
leaf: 0x9000e28 150998568 (16: row:64.64 avs:6780)
leaf: 0x90007da 150996954 (17: row:143.143 avs:5279)
leaf: 0x900025f 150995551 (18: row:54.54 avs:6970)
leaf: 0x9000d03 150998275 (19: row:354.354 avs:1270)
leaf: 0x9000e2f 150998575 (20: row:64.64 avs:6780)
leaf: 0x900017d 150995325 (21: row:64.64 avs:6780)
leaf: 0x9000d45 150998341 (22: row:377.377 avs:833)
leaf: 0x9000e31 150998577 (23: row:239.239 avs:3455)
leaf: 0x9000e05 150998533 (24: row:63.63 avs:6799)
leaf: 0x9000458 150996056 (25: row:377.377 avs:833)
leaf: 0x90007c5 150996933 (26: row:377.377 avs:833)
leaf: 0x900025a 150995546 (27: row:377.377 avs:833)
leaf: 0x9000c29 150998057 (28: row:377.377 avs:833)
leaf: 0x9001149 150999369 (29: row:377.377 avs:833)
leaf: 0x9000732 150996786 (30: row:377.377 avs:833)
leaf: 0x9000e8d 150998669 (31: row:377.377 avs:833)
leaf: 0x9000264 150995556 (32: row:377.377 avs:833)
leaf: 0x90007ec 150996972 (33: row:377.377 avs:833)
leaf: 0x9001042 150999106 (34: row:377.377 avs:833)
leaf: 0x9001131 150999345 (35: row:377.377 avs:833)
leaf: 0x9001125 150999333 (36: row:377.377 avs:833)
leaf: 0x9000ff9 150999033 (37: row:120.120 avs:5716)
leaf: 0x9000784 150996868 (38: row:57.57 avs:6913)
leaf: 0x9000ec6 150998726 (39: row:377.377 avs:833)
leaf: 0x9000924 150997284 (40: row:377.377 avs:833)
leaf: 0x900095f 150997343 (41: row:377.377 avs:833)
leaf: 0x90008cc 150997196 (42: row:377.377 avs:833)
leaf: 0x90008b3 150997171 (43: row:377.377 avs:833)
leaf: 0x9000172 150995314 (44: row:377.377 avs:833)
leaf: 0x90011e5 150999525 (45: row:377.377 avs:833)
leaf: 0x9000ace 150997710 (46: row:377.377 avs:833)
leaf: 0x90011af 150999471 (47: row:377.377 avs:833)
leaf: 0x90005ed 150996461 (48: row:377.377 avs:833)
leaf: 0x90004e4 150996196 (49: row:377.377 avs:833)
leaf: 0x9000795 150996885 (50: row:377.377 avs:833)
leaf: 0x900136f 150999919 (51: row:377.377 avs:833)
leaf: 0x9001338 150999864 (52: row:377.377 avs:833)
leaf: 0x9000fce 150998990 (53: row:377.377 avs:833)
leaf: 0x900127e 150999678 (54: row:377.377 avs:833)
leaf: 0x90013bc 150999996 (55: row:377.377 avs:833)
leaf: 0x9001053 150999123 (56: row:130.130 avs:5526)
leaf: 0x900121d 150999581 (57: row:51.51 avs:7027)
leaf: 0x90004a6 150996134 (58: row:377.377 avs:833)
leaf: 0x90004d4 150996180 (59: row:377.377 avs:833)
leaf: 0x90011be 150999486 (60: row:377.377 avs:833)
leaf: 0x9001160 150999392 (61: row:377.377 avs:833)
leaf: 0x900072c 150996780 (62: row:377.377 avs:833)
leaf: 0x9000d6a 150998378 (63: row:377.377 avs:833)
leaf: 0x900075e 150996830 (64: row:377.377 avs:833)
leaf: 0x900047d 150996093 (65: row:377.377 avs:833)
leaf: 0x9000d5c 150998364 (66: row:377.377 avs:833)
leaf: 0x900074c 150996812 (67: row:377.377 avs:833)
leaf: 0x9000449 150996041 (68: row:377.377 avs:833)
leaf: 0x9000e90 150998672 (69: row:377.377 avs:833)
leaf: 0x900027b 150995579 (70: row:377.377 avs:833)
leaf: 0x9001012 150999058 (71: row:377.377 avs:833)
leaf: 0x9000ec7 150998727 (72: row:377.377 avs:833)
leaf: 0x900104e 150999118 (73: row:377.377 avs:833)
leaf: 0x9000709 150996745 (74: row:377.377 avs:833)
leaf: 0x900027a 150995578 (75: row:377.377 avs:833)
leaf: 0x90007bb 150996923 (76: row:81.81 avs:6457)
leaf: 0x9000f99 150998937 (77: row:47.47 avs:7103)
leaf: 0x90001ea 150995434 (78: row:377.377 avs:833)
leaf: 0x900072a 150996778 (79: row:377.377 avs:833)
leaf: 0x9000429 150996009 (80: row:284.284 avs:2600)
leaf: 0x9000e96 150998678 (81: row:52.52 avs:7008)
leaf: 0x900071a 150996762 (82: row:377.377 avs:833)
leaf: 0x9000273 150995571 (83: row:377.377 avs:833)
leaf: 0x9000749 150996809 (84: row:148.148 avs:5184)
leaf: 0x90001da 150995418 (85: row:65.65 avs:6761)
leaf: 0x9000ef5 150998773 (86: row:377.377 avs:833)
leaf: 0x9000257 150995543 (87: row:377.377 avs:833)
leaf: 0x90007e6 150996966 (88: row:133.133 avs:5469)
branch: 0x900073d 150996797 (5: nrow: 88, level: 1)
leaf: 0x9000143 150995267 (-1: row:377.377 avs:833)
leaf: 0x9000ef7 150998775 (0: row:377.377 avs:833)
leaf: 0x9000a2c 150997548 (1: row:377.377 avs:833)
leaf: 0x9000356 150995798 (2: row:377.377 avs:833)
leaf: 0x9000108 150995208 (3: row:377.377 avs:833)
leaf: 0x9001035 150999093 (4: row:377.377 avs:833)
leaf: 0x9001033 150999091 (5: row:199.199 avs:4215)
leaf: 0x90001c9 150995401 (6: row:51.51 avs:7027)
leaf: 0x900155a 151000410 (7: row:377.377 avs:833)
leaf: 0x90008bc 150997180 (8: row:322.322 avs:1878)
leaf: 0x9000174 150995316 (9: row:68.68 avs:6704)
leaf: 0x900101d 150999069 (10: row:377.377 avs:833)
leaf: 0x9001389 150999945 (11: row:377.377 avs:833)
leaf: 0x90011b0 150999472 (12: row:377.377 avs:833)
leaf: 0x90013b5 150999989 (13: row:377.377 avs:833)
leaf: 0x9000139 150995257 (14: row:377.377 avs:833)
leaf: 0x9000a9c 150997660 (15: row:377.377 avs:833)
leaf: 0x9000652 150996562 (16: row:377.377 avs:833)
leaf: 0x9000bdc 150997980 (17: row:377.377 avs:833)
leaf: 0x90011a6 150999462 (18: row:377.377 avs:833)
leaf: 0x9001256 150999638 (19: row:377.377 avs:833)
leaf: 0x9001535 151000373 (20: row:377.377 avs:833)
leaf: 0x9001358 150999896 (21: row:377.377 avs:833)
leaf: 0x9000590 150996368 (22: row:329.329 avs:1745)
leaf: 0x900154d 151000397 (23: row:48.48 avs:7084)
leaf: 0x90005b9 150996409 (24: row:377.377 avs:833)
leaf: 0x9001355 150999893 (25: row:377.377 avs:833)
leaf: 0x900105d 150999133 (26: row:377.377 avs:833)
leaf: 0x90005c3 150996419 (27: row:377.377 avs:833)
leaf: 0x9000585 150996357 (28: row:377.377 avs:833)
leaf: 0x9000485 150996101 (29: row:369.369 avs:985)
leaf: 0x900091a 150997274 (30: row:48.48 avs:7084)
leaf: 0x9001113 150999315 (31: row:377.377 avs:833)
leaf: 0x90005c6 150996422 (32: row:377.377 avs:833)
leaf: 0x9000486 150996102 (33: row:377.377 avs:833)
leaf: 0x9000ab0 150997680 (34: row:377.377 avs:833)
leaf: 0x9000abc 150997692 (35: row:377.377 avs:833)
leaf: 0x90013ec 151000044 (36: row:338.338 avs:1574)
leaf: 0x900058a 150996362 (37: row:72.72 avs:6628)
leaf: 0x9000bca 150997962 (38: row:54.54 avs:6970)
leaf: 0x90014d0 151000272 (39: row:377.377 avs:833)
leaf: 0x900123f 150999615 (40: row:60.60 avs:6856)
leaf: 0x9000377 150995831 (41: row:44.44 avs:7160)
leaf: 0x9001307 150999815 (42: row:377.377 avs:833)
leaf: 0x9001062 150999138 (43: row:377.377 avs:833)
leaf: 0x900034c 150995788 (44: row:377.377 avs:833)
leaf: 0x900019d 150995357 (45: row:377.377 avs:833)
leaf: 0x9001392 150999954 (46: row:377.377 avs:833)
leaf: 0x9000c6a 150998122 (47: row:377.377 avs:833)
leaf: 0x9000a03 150997507 (48: row:377.377 avs:833)
leaf: 0x9000ac3 150997699 (49: row:377.377 avs:833)
leaf: 0x9000c3f 150998079 (50: row:142.142 avs:5298)
leaf: 0x9001566 151000422 (51: row:61.61 avs:6837)
leaf: 0x9000a82 150997634 (52: row:377.377 avs:833)
leaf: 0x9000355 150995797 (53: row:377.377 avs:833)
leaf: 0x900130c 150999820 (54: row:64.64 avs:6780)
leaf: 0x9000186 150995334 (55: row:58.58 avs:6894)
leaf: 0x9000c76 150998134 (56: row:168.168 avs:4804)
leaf: 0x9000e56 150998614 (57: row:48.48 avs:7084)
leaf: 0x9000471 150996081 (58: row:377.377 avs:833)
leaf: 0x9000a4e 150997582 (59: row:321.321 avs:1897)
leaf: 0x900127c 150999676 (60: row:62.62 avs:6818)
leaf: 0x9000a19 150997529 (61: row:40.40 avs:7236)
leaf: 0x90014d8 151000280 (62: row:377.377 avs:833)
leaf: 0x90005ce 150996430 (63: row:377.377 avs:833)
leaf: 0x9000582 150996354 (64: row:377.377 avs:833)
leaf: 0x900119f 150999455 (65: row:377.377 avs:833)
leaf: 0x900132d 150999853 (66: row:377.377 avs:833)
leaf: 0x9000a77 150997623 (67: row:183.183 avs:4519)
leaf: 0x9000ac2 150997698 (68: row:34.34 avs:7350)
leaf: 0x900137f 150999935 (69: row:331.331 avs:1707)
leaf: 0x9000fbb 150998971 (70: row:51.51 avs:7027)
leaf: 0x90008f6 150997238 (71: row:61.61 avs:6837)
leaf: 0x9001026 150999078 (72: row:377.377 avs:833)
leaf: 0x9001230 150999600 (73: row:377.377 avs:833)
leaf: 0x9001224 150999588 (74: row:377.377 avs:833)
leaf: 0x900103f 150999103 (75: row:377.377 avs:833)
leaf: 0x90011c1 150999489 (76: row:377.377 avs:833)
leaf: 0x90005f3 150996467 (77: row:377.377 avs:833)
leaf: 0x90005fc 150996476 (78: row:377.377 avs:833)
leaf: 0x90004ac 150996140 (79: row:377.377 avs:833)
leaf: 0x9000bb0 150997936 (80: row:377.377 avs:833)
leaf: 0x9000972 150997362 (81: row:377.377 avs:833)
leaf: 0x9000adf 150997727 (82: row:377.377 avs:833)
leaf: 0x9000ab3 150997683 (83: row:377.377 avs:833)
leaf: 0x9000bd6 150997974 (84: row:377.377 avs:833)
leaf: 0x9000650 150996560 (85: row:377.377 avs:833)
leaf: 0x9000607 150996487 (86: row:155.155 avs:5051)
branch: 0x9000c68 150998120 (6: nrow: 101, level: 1)
leaf: 0x90001b2 150995378 (-1: row:362.362 avs:1118)
leaf: 0x9000329 150995753 (0: row:77.77 avs:6533)
leaf: 0x9000bd5 150997973 (1: row:377.377 avs:833)
leaf: 0x900066d 150996589 (2: row:377.377 avs:833)
leaf: 0x90005c5 150996421 (3: row:377.377 avs:833)
leaf: 0x9000497 150996119 (4: row:163.163 avs:4899)
leaf: 0x9001188 150999432 (5: row:54.54 avs:6970)
leaf: 0x9000350 150995792 (6: row:377.377 avs:833)
leaf: 0x900011a 150995226 (7: row:377.377 avs:833)
leaf: 0x900153c 151000380 (8: row:377.377 avs:833)
leaf: 0x900062e 150996526 (9: row:377.377 avs:833)
leaf: 0x900064f 150996559 (10: row:377.377 avs:833)
leaf: 0x90005e7 150996455 (11: row:377.377 avs:833)
leaf: 0x9000482 150996098 (12: row:377.377 avs:833)
leaf: 0x900066f 150996591 (13: row:377.377 avs:833)
leaf: 0x9000bf1 150998001 (14: row:377.377 avs:833)
leaf: 0x900131e 150999838 (15: row:377.377 avs:833)
leaf: 0x90004a3 150996131 (16: row:377.377 avs:833)
leaf: 0x90004a8 150996136 (17: row:377.377 avs:833)
leaf: 0x9000a5b 150997595 (18: row:377.377 avs:833)
leaf: 0x90008ca 150997194 (19: row:377.377 avs:833)
leaf: 0x9000224 150995492 (20: row:377.377 avs:833)
leaf: 0x90007bf 150996927 (21: row:281.281 avs:2657)
leaf: 0x900124e 150999630 (22: row:47.47 avs:7103)
leaf: 0x90005af 150996399 (23: row:181.181 avs:4557)
leaf: 0x9001388 150999944 (24: row:54.54 avs:6970)
leaf: 0x9000a36 150997558 (25: row:377.377 avs:833)
leaf: 0x9000e65 150998629 (26: row:377.377 avs:833)
leaf: 0x9000e67 150998631 (27: row:377.377 avs:833)
leaf: 0x90011a5 150999461 (28: row:377.377 avs:833)
leaf: 0x9001005 150999045 (29: row:377.377 avs:833)
leaf: 0x9000455 150996053 (30: row:377.377 avs:833)
leaf: 0x9001376 150999926 (31: row:377.377 avs:833)
leaf: 0x90008a6 150997158 (32: row:377.377 avs:833)
leaf: 0x900095b 150997339 (33: row:377.377 avs:833)
leaf: 0x9001060 150999136 (34: row:377.377 avs:833)
leaf: 0x9001138 150999352 (35: row:377.377 avs:833)
leaf: 0x90007dc 150996956 (36: row:292.292 avs:2448)
leaf: 0x9000eff 150998783 (37: row:69.69 avs:6685)
leaf: 0x900040b 150995979 (38: row:377.377 avs:833)
leaf: 0x90005f1 150996465 (39: row:377.377 avs:833)
leaf: 0x9001127 150999335 (40: row:320.320 avs:1916)
leaf: 0x9000af2 150997746 (41: row:74.74 avs:6590)
leaf: 0x9000588 150996360 (42: row:35.35 avs:7331)
leaf: 0x90014a4 151000228 (43: row:377.377 avs:833)
leaf: 0x9000ae8 150997736 (44: row:377.377 avs:833)
leaf: 0x9001164 150999396 (45: row:377.377 avs:833)
leaf: 0x9001155 150999381 (46: row:377.377 avs:833)
leaf: 0x90004ad 150996141 (47: row:179.179 avs:4595)
leaf: 0x900035e 150995806 (48: row:37.37 avs:7293)
leaf: 0x900116f 150999407 (49: row:139.139 avs:5355)
leaf: 0x90005a5 150996389 (50: row:45.45 avs:7141)
leaf: 0x90014db 151000283 (51: row:377.377 avs:833)
leaf: 0x9001176 150999414 (52: row:377.377 avs:833)
leaf: 0x90004da 150996186 (53: row:377.377 avs:833)
leaf: 0x90004e6 150996198 (54: row:377.377 avs:833)
leaf: 0x9000ee7 150998759 (55: row:377.377 avs:833)
leaf: 0x9000e5c 150998620 (56: row:377.377 avs:833)
leaf: 0x900021a 150995482 (57: row:377.377 avs:833)
leaf: 0x90008a9 150997161 (58: row:340.340 avs:1536)
leaf: 0x90004b1 150996145 (59: row:64.64 avs:6780)
leaf: 0x90011f8 150999544 (60: row:111.111 avs:5887)
leaf: 0x900157e 151000446 (61: row:42.42 avs:7198)
leaf: 0x900021f 150995487 (62: row:377.377 avs:833)
leaf: 0x9001270 150999664 (63: row:230.230 avs:3626)
leaf: 0x900117e 150999422 (64: row:58.58 avs:6894)
leaf: 0x900048a 150996106 (65: row:377.377 avs:833)
leaf: 0x90004be 150996158 (66: row:377.377 avs:833)
leaf: 0x90005f8 150996472 (67: row:291.291 avs:2467)
leaf: 0x9000aaf 150997679 (68: row:72.72 avs:6628)
leaf: 0x9000595 150996373 (69: row:377.377 avs:833)
leaf: 0x90014ab 151000235 (70: row:163.163 avs:4899)
leaf: 0x9000344 150995780 (71: row:54.54 avs:6970)
leaf: 0x90013ef 151000047 (72: row:377.377 avs:833)
leaf: 0x9000971 150997361 (73: row:377.377 avs:833)
leaf: 0x9000922 150997282 (74: row:377.377 avs:833)
leaf: 0x900090f 150997263 (75: row:377.377 avs:833)
leaf: 0x9000b82 150997890 (76: row:134.134 avs:5450)
leaf: 0x900062b 150996523 (77: row:78.78 avs:6514)
leaf: 0x9000ba5 150997925 (78: row:377.377 avs:833)
leaf: 0x9001488 151000200 (79: row:377.377 avs:833)
leaf: 0x9001212 150999570 (80: row:377.377 avs:833)
leaf: 0x9000ba0 150997920 (81: row:324.324 avs:1840)
leaf: 0x9000c41 150998081 (82: row:81.81 avs:6457)
leaf: 0x9000676 150996598 (83: row:84.84 avs:6400)
leaf: 0x9000c75 150998133 (84: row:244.244 avs:3360)
leaf: 0x9000610 150996496 (85: row:82.82 avs:6438)
leaf: 0x9000c33 150998067 (86: row:377.377 avs:833)
leaf: 0x9000bd9 150997977 (87: row:198.198 avs:4234)
leaf: 0x9000c6b 150998123 (88: row:79.79 avs:6495)
leaf: 0x900014d 150995277 (89: row:294.294 avs:2410)
leaf: 0x9000475 150996085 (90: row:80.80 avs:6476)
leaf: 0x9000d2b 150998315 (91: row:161.161 avs:4937)
leaf: 0x9000c11 150998033 (92: row:74.74 avs:6590)
leaf: 0x9000275 150995573 (93: row:377.377 avs:833)
leaf: 0x9000c5c 150998108 (94: row:377.377 avs:833)
leaf: 0x900064e 150996558 (95: row:377.377 avs:833)
leaf: 0x9000c57 150998103 (96: row:310.310 avs:2106)
leaf: 0x9000c42 150998082 (97: row:61.61 avs:6837)
leaf: 0x9000651 150996561 (98: row:377.377 avs:833)
leaf: 0x9000bbe 150997950 (99: row:94.94 avs:6210)
----- end tree dump
shrink space compact
When we switch to “alter index shrink space compact” (which is the version that doesn’t lower the index highwater mark), the first striking difference appears in the dbms_space report:
Unformatted : 62 / 507,904
Freespace 1 ( 0 - 25% free) : 0 / 0
Freespace 2 ( 25 - 50% free) : 1 / 8,192
Freespace 3 ( 50 - 75% free) : 0 / 0
Freespace 4 ( 75 - 100% free) : 3,045 / 24,944,640
Full : 544 / 4,456,448
PL/SQL procedure successfully completed.
Segment Total blocks: 3,712
Object Unused blocks: 0
Basically we had 3,000 blocks reported as Freespace 2 after a coalesce, but now we see those blocks reported as Freespace 4. Are they in the index structure, have they been unlinked, and is the undo/redo going to show anything significantly different because of this change.
In a single stream, here are the things we need to cross-reference to get a better view of what Oracle has done. Some critical redo stats, the undo segment stats and the report of enqueue requests:
Name Value
---- -----
redo entries 47,521
redo size 85,285,860
redo buffer allocation retries 13
undo change vector size 59,344,340
rollback changes - undo records applied 447
USN Ex Size K HWM K Opt K Writes Gets Waits Shr Grow Shr K Act K
---- -- ------ ----- ----- ------ ---- ----- --- ---- ----- ------
0 0 0 0 0 0 1 0 0 0 0 0
1 0 0 0 0 0 25 0 0 0 0 0
2 0 0 0 0 0 25 0 0 0 0 0
3 0 0 0 0 0 25 0 0 0 0 0
4 -30 -29760 0 0 328 75 0 3 0 55 0
5 0 0 0 0 0 25 0 0 0 0 0
6 0 0 0 0 0 25 0 0 0 0 0
7 0 0 0 0 0 25 0 0 0 0 0
8 -41 -37952 0 0 410 96 0 5 0 65 0
9 104 85056 0 0 58635908 14524 0 0 104 0 148492
10 0 0 0 0 0 25 0 0 0 0 0
Type Requests Waits Success Failed Wait m/s Reason
---- -------- ----- ------- ------ -------- ------
CF 2 0 2 0 0 contention
CR 710 17 710 0 2 block range reuse ckpt
IS 71 0 71 0 0 contention
XR 1 0 1 0 0 database force logging
TM 1 0 1 0 0 contention
TX 3,567 0 3,567 0 0 contention
US 116 0 116 0 0 contention
HW 348 0 348 0 0 contention
SK 1 0 1 0 0 contention
TT 232 0 232 0 0 contention
SJ 2 0 2 0 0 Slave Task Cancel
CU 1 0 1 0 0 contention
JG 357 0 357 0 0 queue lock
JG 34 0 34 0 0 q mem clnup lck
JG 357 0 357 0 0 contention
The redo requirement has increased from 34,800 enries and 76MB to 47,500 entries and 85MB; aided by an increase of 4MB in the undo. Cross-checking to the undo segment stats (v$rollstat) we see an alarming difference – the volume of writes agrees with the session stats, but almost all of it takes place on one undo segment; that could be really nasty if it means the whole shrink is performed as a single transaction!
Luckily we can see in the enqueue stats that we still have a large number of transaction (TX) enqueues, though the number has gone up from about 3,000 to 3,500. (That’s an interesting difference given the “shrunk” index consists of about 500 leaf blocks – and while we’re thinking about that, it might be interesting that 4MB of undo seems to be approximately 500 (leaf?) blocks * 8KB!)
Let’s take a look at the before and after versions of the treedump. Because I was using a clean tablespace to re-run the tests, and because I managed to keep restarting on the same v$process.pid for many of the tests the order in which I used data blocks was unchanged from test to test, so the index for the “compact” test started out exactly the same as it was for the “coalesce” test:
Before
branch: 0x9000104 150995204 (0: nrow: 8, level: 2)
branch: 0x9000438 150996024 (-1: nrow: 401, level: 1)
leaf: 0x900016d 150995309 (-1: row:222.47 avs:3778)
leaf: 0x900154e 151000398 (0: row:218.52 avs:3854)
leaf: 0x9000abd 150997693 (1: row:219.44 avs:3835)
leaf: 0x900153e 151000382 (2: row:209.43 avs:4025)
leaf: 0x900058d 150996365 (3: row:230.44 avs:3626)
leaf: 0x90013a8 150999976 (4: row:229.45 avs:3645)
leaf: 0x9000ae1 150997729 (5: row:411.88 avs:187)
leaf: 0x900031c 150995740 (6: row:227.50 avs:3683)
leaf: 0x90014d3 151000275 (7: row:229.42 avs:3645)
leaf: 0x9000aec 150997740 (8: row:226.46 avs:3702)
leaf: 0x90014f3 151000307 (9: row:226.57 avs:3702)
leaf: 0x9000593 150996371 (10: row:219.46 avs:3835)
leaf: 0x9001559 151000409 (11: row:223.54 avs:3759)
leaf: 0x9000a9d 150997661 (12: row:210.33 avs:4006)
leaf: 0x900152e 151000366 (13: row:215.30 avs:3911)
leaf: 0x900018a 150995338 (14: row:258.52 avs:3094)
After
branch: 0x9000104 150995204 (0: nrow: 8, level: 2)
branch: 0x9000427 150996007 (-1: nrow: 64, level: 1)
leaf: 0x900016d 150995309 (-1: row:377.377 avs:833)
leaf: 0x900011b 150995227 (0: row:377.377 avs:833)
leaf: 0x900016e 150995310 (1: row:377.377 avs:833)
leaf: 0x9000370 150995824 (2: row:377.377 avs:833)
leaf: 0x900011e 150995230 (3: row:377.377 avs:833)
leaf: 0x9000309 150995721 (4: row:377.377 avs:833)
leaf: 0x9000239 150995513 (5: row:377.377 avs:833)
leaf: 0x90001eb 150995435 (6: row:377.377 avs:833)
leaf: 0x90001d3 150995411 (7: row:377.377 avs:833)
leaf: 0x9000197 150995351 (8: row:377.377 avs:833)
leaf: 0x900031f 150995743 (9: row:377.377 avs:833)
leaf: 0x9000369 150995817 (10: row:377.377 avs:833)
leaf: 0x9000216 150995478 (11: row:377.377 avs:833)
leaf: 0x9000332 150995762 (12: row:377.377 avs:833)
leaf: 0x900023b 150995515 (13: row:377.377 avs:833)
leaf: 0x900033a 150995770 (14: row:377.377 avs:833)
A particularly interesting detail of the “after compact” treedump appears in the first (highlighted) level 1 branch block: it has changed its address (even though its first leaf block hasn’t).
A less obvious detail in the after compact extract is that none of the leaf block addresses is particularly large. Before compacting some of the block addresses ended with 4 non-zero digits, after compacting the highest block address we can see is 0x9000370 with only 3 trailing non-zero digits. And if we sort all the leaf blocks by block address we see the following:
leaf: 0x9000105 150995205 (59: row:377.377 avs:833)
leaf: 0x9000106 150995206 (37: row:377.377 avs:833)
leaf: 0x9000107 150995207 (5: row:377.377 avs:833)
leaf: 0x9000108 150995208 (3: row:377.377 avs:833)
leaf: 0x9000109 150995209 (29: row:377.377 avs:833)
leaf: 0x900010a 150995210 (52: row:377.377 avs:833)
leaf: 0x900010b 150995211 (35: row:377.377 avs:833)
leaf: 0x900010c 150995212 (53: row:377.377 avs:833)
leaf: 0x900010d 150995213 (28: row:377.377 avs:833)
leaf: 0x900010e 150995214 (60: row:377.377 avs:833)
leaf: 0x900010f 150995215 (10: row:377.377 avs:833)
...
leaf: 0x9000428 150996008 (8: row:377.377 avs:833)
leaf: 0x9000429 150996009 (20: row:377.377 avs:833)
leaf: 0x900042a 150996010 (19: row:377.377 avs:833)
leaf: 0x900042b 150996011 (8: row:377.377 avs:833)
leaf: 0x900042c 150996012 (55: row:377.377 avs:833)
With a few small gaps for the space management blocks and a couple of big jumps where table extents have been allocated between index extents, we can see a completely contiguous array of blocks. (And this “shuffling” of blocks explains most of the extra undo, redo and transaction count.)
There is the question, of course, of whether Oracle does all the back-filling before rearranging the blocks, or whether it relocates a block as soon as it has filled it. There’s a fairly big hint in the quote from the manuals that said: “Concurrent DML operations are blocked for a short time at the end of the shrink operation when the space is deallocated” but we can answer the question fairly easily by looking at the redo log that we’ve dumped.
If we use grep to pick out just the index-related OP Codes (layer 10) and the 5.4 (commit) OP codes and look at the last few lines of the result we can spot a repeating pattern like the following (which I’ve edited to shorten the lines):
DBA:0x09000c24 OBJ:143721 SCN:0x0000000002542c13 SEQ:1 OP:10.6
DBA:0x09001674 OBJ:143721 SCN:0x0000000002542c13 SEQ:1 OP:10.6
DBA:0x09000105 OBJ:143721 SCN:0x0000000002542c13 SEQ:1 OP:10.8
DBA:0x0900033c OBJ:143721 SCN:0x0000000002542c13 SEQ:1 OP:10.11
DBA:0x09000c24 OBJ:143721 SCN:0x0000000002542c13 SEQ:2 OP:10.11
DBA:0x09000e5b OBJ:143721 SCN:0x0000000002542c13 SEQ:1 OP:10.40
DBA:0x09001674 OBJ:143721 SCN:0x0000000002542c13 SEQ:2 OP:10.34
DBA:0x04402720 OBJ:4294967295 SCN:0x0000000002542c13 SEQ:2 OP:5.4
This, plus a few variations, happens 441 times at the end of the dump. The OP Codes translate to:
- Lock block 0x09000c24 (10.6)
- Lock block 0x09001674 (10.6)
- Initialize leaf block 0x09000105 (10.8) — copying block 0x009001674
- Set previous pointer on leaf block 0x0900033c (10.11) — to point backwards to 0x009000105
- Set next pointer on leaf block 0x09000c24 (10.11) — to point forwards to 0x009000105
- Update branch block 0x009000e5b (10.40) — to point to 0x009000105 instead of 0x009001674
- Make empty leaf block 0x09001674 (10.34)
- commit (5.4)
This pattern shows Oracle copying leaf blocks to the start of the segment and wiping the original clean (the small number of variants are for branch blocks). And this happens only after the task of filling all the leaf blocks to the correct level has finished.
As before it’s the initialize (10.8) and the undo (5.1) of the “make empty” (10.34) which generate the largest amount of redo – the 10.8 being effectively an array insert of 377 rows, and the 5.1 being an 8KB block image.
There are other (relatively small) differences, though between the redo log dump for coalesce and compact. We noted that the 3,000 “empty” blocks were marked as FS2 for the coalesce but FS4 for the compact. When we compare the OP Code 13.22 (state change for Level 1 BMB) we find that the coalesce reported roughly 3,000 of them them with the specific action “Mark Block free”; but compact reported 6,900 of them of which 3,900 reports “Mark Block free” and 3,027 of them reported “State Change”. That’s an interesting difference when the space management report tells us that there were 3,027 blocks at FS4 when I had been expecting them to be FS2.
A little detail on the side – the sort of thing that goes into a note for further investigation – is that the redo for the compact reported 8 cases of Op Code 13.22 redo change vectors as “Update Express Allocation Area” in the first level 1 bitmap of the segment for Allocate Area slots 0 to 7 respectively, and had one 13.28 Op Code (Update segment header block) with the same description, supposedly marking the Allocation Area “Full”.
A little extra work with grep (looking for “OP:13.22” or “state:”, and then looking at a few lines of the raw trace very closely, then doing a couple more “grep”s led me to the following summary report:
egrep -n -i -e "offset:.*state:" -e"state:" *compact*redo*.trc
...
101824:offset: 10 length:1 xidslot:35 state:3
102992:offset: 34 length:1 xidslot:35 state:3
104239:offset: 38 length:1 xidslot:35 state:3
105544:offset: 46 length:1 xidslot:35 state:3
106876:offset: 15 length:1 xidslot:35 state:3
108485:offset: 55 length:1 xidslot:35 state:3
109678:offset: 49 length:1 xidslot:35 state:3
110960:offset: 16 length:1 xidslot:35 state:3
...
3889253:Len: 1 Offset: 63 newstate: 2
3889261:Len: 1 Offset: 62 newstate: 2
3889269:Len: 1 Offset: 61 newstate: 2
3889283:Len: 1 Offset: 60 newstate: 2
3889297:Len: 1 Offset: 59 newstate: 2
3889305:Len: 1 Offset: 58 newstate: 2
3889313:Len: 1 Offset: 57 newstate: 2
3889327:Len: 1 Offset: 56 newstate: 2
3889341:Len: 1 Offset: 55 newstate: 2
3889349:Len: 1 Offset: 54 newstate: 2
3889357:Len: 1 Offset: 53 newstate: 2
3890375:offset: 52 length:1 xidslot:35 state:3
3890387:Len: 1 Offset: 52 newstate: 2
3890400:Len: 1 Offset: 51 newstate: 2
...
The early part of the trace file shows the bitmap changes as index entries are transferred to the (logically) previous index leaf block and a leaf block becomes empty: its “bit” is set to state 3 (which corresponds to FS2). The offset is the location of the “bit” in the space management block and in some cases a range of bits can be set in one call, hence the presence of the length. I haven’t shown you the DBA (block address) of the OP:13.22 which jumps all over the place as Oracle walks the index in key order, but that explains the randomness of the offset – with my 1MB extent definition each bitmap block maps 64 consecutive data blocks from the 128 available to the extent and (logically) consecutive leaf blocks could be in different extents.
In the later part of the trace file – once the rows have been packed into the minimum number of leaf blocks – Oracle starts walking the index “backwards” in “physical” – i.e. from the last block of the last used extrent – again you really need to see some way of viewing DBAs but there’s a hint in the way the offset decreases from 63 to zero.
If Oracle finds an empty (state 3) block it changes it to state 2 (which corresponds to FS4). If it finds a leaf block that is not empty (highlighted lines) it goes through the steps described above to “create full block as near as possible to the start of the segment” / “create empty block here” and flags the empty block as state 3 – and then changes the state from 3 to 2. (You don’t see a state change for the block created near the start of segment as it will be overwriting a pre-existing “full” block. The block changes, the bit doesn’t have to.)
The DBAs you can dump are the ones for all the OP:10.8 (initialize new block). In the earlier part of the trace you’ll see the DBA’s in these records jumping about randomly as Oracle walks the index in key order (each one may appear several times in a row as several consecutive leaf blocks may empty themselves backwards into a single leaf block – which is what happened after my 80% deletion). In the later part of the trace file it will probably be fairly easy to see that the “new” blocks are working forwards from the start of the segment. Here’s a little bit of the dump from the later part of my trace file:
3889458:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x09000105 OBJ:143721 SCN:0x0000000002542c13 SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3890921:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x09000107 OBJ:143721 SCN:0x0000000002542c60 SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3892086:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x09000108 OBJ:143721 SCN:0x0000000002542c73 SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3893167:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x09000109 OBJ:143721 SCN:0x0000000002542c7a SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3894276:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x0900010a OBJ:143721 SCN:0x0000000002542c85 SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3895861:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x0900010b OBJ:143721 SCN:0x0000000002542cd4 SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3896968:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x0900010c OBJ:143721 SCN:0x0000000002542cdd SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3898133:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x0900010d OBJ:143721 SCN:0x0000000002542cf0 SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3899214:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x0900010e OBJ:143721 SCN:0x0000000002542cf7 SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3900295:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x09000110 OBJ:143721 SCN:0x0000000002542cfe SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3901348:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x09000111 OBJ:143721 SCN:0x0000000002542d01 SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3902555:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x09000112 OBJ:143721 SCN:0x0000000002542d1a SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
3903608:CHANGE #2 CON_ID:3 TYP:0 CLS:1 AFN:36 DBA:0x09000114 OBJ:143721 SCN:0x0000000002542d1d SEQ:1 OP:10.8 ENC:0 RBL:0 FLG:0x0000
So we can see that blocks made empty by the block-shuffling of a “shrink space” on an index are flagged as “state 2”, which then gets reported by dbms_space.space_usage() as FS4, i.e. “75 – 100% free”. It seems a little odd that this should be the case (especially when (a) coalesce and deletes use state 3 / FS2 and (b) shrink space compact marks them as state 3 before immediately changing them to state 2. Possibly, though, this is a little trick to avoid the risk of error when Oracle tries to reduce the highwater mark on a “shrink space”, or to avoid repeating work if this phase of the operation is interrupted and has to be interrupted.
Note, however, another little performance threat indicated by this processing. Oracle walks the index in key order to collapse the contents of multiple leaf blocks back to an existing single leaf block. rows; then it re-reads the index in reverse order of extent_id (and block_id within extent – where necessary) as it moves blocks from the high end of the segment to the low end of the segment. For a very large index you may end up physically reading most of it twice, one block at a time.
Shrink space compact – concurrency
The manuals tell us that the “compact” option of shrink space allows the command to complete “online” – i.e. with other activity ongoing. How accurate is this description? Let’s just re-run the test but insert a few randomly scattered values from another session without committing before we start the shrink, and see what happens:
My test data is tiny and my laptop is fairly high powered, so the session doing the shrinking seemed to hang almost instantly, going into a wait for a TX enqueue, timing out every three seconds. When I commited from the second session the shrink finished almost instantly – so three possibilities:
- It had waited for all TM locks to drop before starting work
- It had hit the first leaf block with an active transaction and waited for that transaction to commit before continuing
- It had skipped over any leaf block with an active transaction and only gone into a TX wait on the “phase 2” when it was trying to move leaf blocks towards the start of the segment.
Fortunately I had done a treedump of the index before committing, with the following results (first few lines only):
branch: 0x9000104 150995204 (0: nrow: 8, level: 2)
branch: 0x900042b 150996011 (-1: nrow: 81, level: 1)
leaf: 0x9000167 150995303 (-1: row:377.377 avs:833)
leaf: 0x9000126 150995238 (0: row:377.377 avs:833)
leaf: 0x90001b8 150995384 (1: row:377.377 avs:833)
leaf: 0x9000354 150995796 (2: row:242.242 avs:3398)
leaf: 0x9000139 150995257 (3: row:45.45 avs:7141)
leaf: 0x900034d 150995789 (4: row:377.377 avs:833)
leaf: 0x9000337 150995767 (5: row:377.377 avs:833)
...
Most of the index had been through the row-packing process, but there were clear indications that Oracle had handled a few leaf blocks differently (lines 6 & 7). Moreover there were some very strange leaf blocks reporting “row:0.0” – all of which had a “high” block address:
leaf: 0x9000335 150995765 (64: row:377.377 avs:833)
leaf: 0x900015e 150995294 (65: row:308.308 avs:2144)
leaf: 0x9000148 150995272 (66: row:50.50 avs:7046)
leaf: 0x9000a36 150997558 (67: row:0.0 avs:7996)
leaf: 0x9000356 150995798 (68: row:37.37 avs:7293)
leaf: 0x900014e 150995278 (69: row:377.377 avs:833)
After I’d committed the second session and the shrink space compact had completed this portion of the index changed to:
leaf: 0x9000335 150995765 (64: row:377.377 avs:833)
leaf: 0x900015e 150995294 (65: row:308.308 avs:2144)
leaf: 0x9000148 150995272 (66: row:50.50 avs:7046)
leaf: 0x9000356 150995798 (67: row:37.37 avs:7293)
leaf: 0x900014e 150995278 (68: row:377.377 avs:833)
So it seems that Oracle works its way through the entire compaction process but leaves an empty block for each leaf block above the “anticipated” highwater mark (to allow for easy read-consistency, perhaps) and then waits for each transaction that is holding one of those blocks to commit before removing them from the index structure.
We can do one last check to see if this hypothesis is roughly what happens by looking at the redo log dump and checking timestamps to see when the big TX wait stops and what happens after it is over – and here are some lines from the redo dump showing the last few OP:13.22 codes with their associated timestamps and line numbers
4364620:CHANGE #1 CON_ID:3 TYP:0 CLS:8 AFN:36 DBA:0x09000480 OBJ:143917 SCN:0x00000000025609a6 SEQ:1 OP:13.22 ENC:0 RBL:0 FLG:0x0000
4364629:SCN: 0x00000000025609a7 SUBSCN: 1 09/05/2022 12:15:38
4364632:CHANGE #2 CON_ID:3 TYP:0 CLS:8 AFN:36 DBA:0x09000480 OBJ:143917 SCN:0x00000000025609a6 SEQ:2 OP:13.22 ENC:0 RBL:0 FLG:0x0000
4364638:SCN: 0x00000000025609a7 SUBSCN: 1 09/05/2022 12:15:38
...
4373099:CHANGE #1 CON_ID:3 TYP:0 CLS:8 AFN:36 DBA:0x09001100 OBJ:143917 SCN:0x000000000255f937 SEQ:1 OP:13.22 ENC:0 RBL:0 FLG:0x0000
4373105:SCN: 0x0000000002560b1f SUBSCN: 1 09/05/2022 12:20:14
...
4373283:CHANGE #1 CON_ID:3 TYP:0 CLS:8 AFN:36 DBA:0x09000a00 OBJ:143917 SCN:0x00000000025602b1 SEQ:2 OP:13.22 ENC:0 RBL:0 FLG:0x0000
4373289:SCN: 0x0000000002560b24 SUBSCN: 1 09/05/2022 12:20:14
...
4373466:CHANGE #1 CON_ID:3 TYP:0 CLS:8 AFN:36 DBA:0x09000581 OBJ:143917 SCN:0x0000000002560886 SEQ:2 OP:13.22 ENC:0 RBL:0 FLG:0x0000
4373472:SCN: 0x0000000002560b28 SUBSCN: 1 09/05/2022 12:20:14
4373479:SCN: 0x0000000002560b28 SUBSCN: 1 09/05/2022 12:20:14
4373485:SCN: 0x0000000002560b28 SUBSCN: 1 09/05/2022 12:20:14
4373486:CHANGE #1 CON_ID:3 TYP:0 CLS:8 AFN:36 DBA:0x09000480 OBJ:143917 SCN:0x00000000025609a7 SEQ:1 OP:13.22 ENC:0 RBL:0 FLG:0x0000
4373492:SCN: 0x0000000002560b2a SUBSCN: 1 09/05/2022 12:20:14
4373499:SCN: 0x0000000002560b2a SUBSCN: 1 09/05/2022 12:20:14
Note the 5 minute gap between the updates to the level 1 bitmap block 0x09001100 and block 0x09000480, which was one of the 3 “problem” blocks with the unusual “row:0.0” entry in the treedump.
One last little detail to highlight mechanisms – if I sort the leaf blocks from the treedump I took while the shrink was waiting this is what the last few lines looks like:
leaf: 0x90004ac 150996140 (77: row:70.70 avs:6666)
leaf: 0x90004ad 150996141 (69: row:377.377 avs:833)
leaf: 0x90004ae 150996142 (54: row:49.49 avs:7065)
leaf: 0x90004af 150996143 (6: row:377.377 avs:833)
leaf: 0x90004b0 150996144 (52: row:377.377 avs:833)
leaf: 0x90004b1 150996145 (70: row:377.377 avs:833)
leaf: 0x90005ed 150996461 (41: row:0.0 avs:7996)
leaf: 0x9000a36 150997558 (67: row:0.0 avs:7996)
leaf: 0x9001105 150999301 (9: row:0.0 avs:7996)
Check the last three “outliers” in this list and compare them with the bitmap updates recorded after the 5 minute wait. (The very last OP:13.22 – to block 0x9000480 – is the change from state 3 to state 2.) Oracle does as much as it can as soon as it can, and then clears up the last few messy bits while letting everything else go on without interruption. You may find, however, that the strategy of bypassing and returning to leaf blocks that hold active transactions may – depending on the pattern of data – result in a large number of blocks that Oracle has not been able to pack to the greatest possible extent.
If you have a large number of small transactions executing and committing you’ll see the same sort of effect. The impact on the final size of the index and the number of blocks that haven’t achieved maximum utilisation) will depend very much on the data patterns and the nature of processing done by the competing sessions.
If we need to investgate further, we can always examine the ksq trace. There are a couple of details in this that vary vary from the coalesce trace. We see the same TM enqueue in mode 2 held for the duration of the process, but instead of an OD enqueue we see an SK enqueue (segment shrink) taken immediately after the TM enqueue and held to the very end of processing.
In the second phase of the processing, as leaf blocks are copied into blocks nearer the start of the segment we see TX enqueues being taken in mode 4 as the process reaches a block that is still holding an active transaction; but this is no different from the normal action for “wait for competing transaction to commit or rollback”, and the enqueue is released as soon as the other session commits.
shrink space (without compact)
I find it fairly amusing that you have to extend the shrink space command if you want it to do less work. Perhaps if it were “compact only” that would feel less strange.
If you omit the “compact” option Oracle moves the highwater mark down the segment to release as many extents as possible back to the tablespace. This was immediately visible in the space management report:
Unformatted : 0 / 0
Freespace 1 ( 0 - 25% free) : 0 / 0
Freespace 2 ( 25 - 50% free) : 2 / 16,384
Freespace 3 ( 50 - 75% free) : 0 / 0
Freespace 4 ( 75 - 100% free) : 0 / 0
Full : 544 / 4,456,448
PL/SQL procedure successfully completed.
Segment Total blocks: 640
Object Unused blocks: 82
Critically the Segment Total blocks has dropped to 640: that’s 5 extents of 128 blocks each (remember my tablespace was declared with 1MB uniform extents).
When, to be awkward, I created the index in a tablespace declared with system-allocated extents, and gave it a storage clause of (initial 1M next 8M), it shrank to two extents, one of 128 blocks and one of 440 blocks (rather than the 1,024 blocks implied by the declaration). So shrinking indexes can result in some fairly randomly sized holes in the tablespace – the effect is similar to the trimming that takes place with parallel “create table as select” and “create index”. The effect isn’t a total mess, though, since it is catering for the 1MB, 8MB, 64MB “boundaries” of system-allocated tablespaces and not a purely random trim.
So the next thing we need to look at is the locking that’s going on, and any collateral mechanisms that show us the work Oracle does as it’s adjusting the highwater mark and releasing the extents to the tablespace.
Shrink Space – locking
There was very little difference in volume of undo and redo when comparing shrink space compact with shrink space – the latter averaged a little more than the former, but with the variations due to the occasional restarts and the undo segment stealing the difference wasn’t significant. Critically, of course, there there were a number of extra transations due to the “spare” extents being dropped as the highwater mark was lowered. Each extent dropped required an update to the seg$ table, and each update was executed as a separate transaction – interestingly, although the undo generated by the shrinking was all dumped into a single undo segment, the recursive dropping of the extents rotated through the available undo segments, producting the following type of figures for the rollback statistics:
USN Ex Size K HWM K Opt K Writes Gets Waits Shr Grow Shr K Act K
---- -- ------ ----- ----- ------ ---- ----- --- ---- ----- ------
0 0 0 0 0 0 1 0 0 0 0 0
1 0 0 0 0 2426 92 0 0 0 0 0
2 0 0 0 0 782 82 0 0 0 0 0
3 0 0 0 0 3410 102 0 0 0 0 0
4 0 0 0 0 1612 87 0 0 0 0 0
5 0 0 0 0 1260 87 0 0 0 0 0
6 416 91584 0 0 60289862 16521 0 0 416 0 -62613
7 0 0 0 0 5202 130 0 0 0 0 0
8-380 -90616 0 0 5828 629 0 38 0 -24 0
9 0 0 0 0 1582 89 0 0 0 0 0
10 0 0 0 0 1468 87 0 0 0 0 0
You’ll notice that most of the undo segments saw a few writes. A particular side-note in this set of results is the effect on undo segment 8 – while segment 6 grew by 90MB this was at the cost of segment 8 shrinking by 90MB. If you try to shrink several segments one after the other you could seriously disrupt any other long-running activity on the system as each shrink steals (possibly “unexpired”) extents from other undo segments as it grows. (You might even see some time spent waiting on the “US” (undo segment) and “CR” enqueues.)
One of the surprising details of the final phase of the shrink space command was that the TM lock on the underlying table was taken and released twice (in mode 6) after the mode 2 for the phases 1 and 2 was released. Given the number and timing of the CR (reuse block range) enqueues that appeared around this time it’s possible that the first lock was held while the redundant extents were forced to disc, and the second was held while the segment header and extent map blocks were updated and forced to disc. The SK enqueue taken at the very start of the shrink was was held all the way through this processing.
Shrink Space – concurrency
As before concurrent transactions will run uninterrupted but skipping blocks which are subject to active transactions in “phase 1”; then in “phase 2” as blocks are copied from the high end of the segment to the low end of the segment the shrink will wait for each block that is still subject to an active transaction. The concurrency is good, as the bulk of the work takes place while the shrinking session is holding its TM lock in mode 2.
When we get to the moment when extents are de-allocated and the highwater marks adjusted the session takes and releases two TM locks in mode 6 in rapid succession. If another session manages to update a row (i.e. taking a TM/3 lock on the table) before the shrink session gets its first TM/6 lock the shrinking session will have to wait for the session to commit. It does this in the normal fashion – timing out and restarting every 3 seconds, and checking for a local deadlock every 60 seconds. So any transaction that manages to slip in to update the table between the shrink and the release of space could cause the table to be locked indefinitely. This doesn’t appear to be any worse than the problem introduced by the waits for “locked” leaf blocks as the “compact” tries to copy them towards the start of the segment, though.
Summary (so far)
alter index xxx coalesce is an online operation which reads through the index in order, copying index entries backwards to fill leaf blocks (according to the pctfree setting). This is not a row-by-row process, the session constructs full leaf blocks in private memory and “initialises” them into the database, re-initialising any blocks that have been made empty at the same time. The leaf block that was the last one to contribute index entries to the full block will be used as the target for the next fill – unless the transfer process left it completely empty in which case Oracle starts with the next leaf block in the index.
When the process empties a leaf block, Oracle unlinks it from the index structure. This means deleting an entry from the level 1 branch block and modifying the two leaf blocks either side of the empty block so that the “next pointer” of the previous block points to the next leaf block, and the “previous pointer” of the next block points to the previous block. The bitmap entry for the the empty block can then be set to report it as “Freespace 2” – ready for re-use anywhere else in the index.
The copy-back process doesn’t cross the boundaries of level 1 branch blocks, so the last leaf block for a branch block may not reach the limit of rows it’s allowed to hold. Also the first leaf block of a branch block is never substituted, and it may (for reasons I don’t know) end up holding less than the expected maximum row count.
It is possible to make a reasonably estimate of the undo and redo generated by a call to coalesce an index.
The coalesce operates as a large number of small transactions (working through the index on pairs of adjacent blocks) and will cycle through all the undo segments in your undo tablespace.
If a coalesce reaches a block that holds an active transaction it will skip the block and move on to the next available leaf block, so a little light activity on the index could significantly reduce the effectiveness of the coalesce and different indexes on the same table could be affected very differently because of the pattern that exist in the data and its indexes.
alter index xxx shrink space [compact] is a two or three phase process depending on whether you include the compact option or not. The first phase seems to be very similar to the work done by the coalesce command and, like the coalesce command, operates as a large number of small transactions, skipping any leaf blocks that contain an active transaction. This allows it to be an online process.
After packing as many leaf blocks as much as possible, shrink space moves into “phase 2” where it copies leaf blocks from the “end” of the segment to empty blocks near the beginning of the segment, working backwards down the extents and blocks. If it finds a leaf block with an active transaction while doing this it waits for the transaction to commit using the normal TX mode 4 wait.
At the end of phase 2 the index is packed into the smallest set of blocks at the low end of the segment and all the other blocks allocated below the highwater mark are flagged as “FS4” (75 – 100% free), unlike the blocks for a coalesce which are flagged as “FS2” (25 – 50% free). In both cases this actually means “empty and available for reuse”.
Like the coalesce command “shrink space” holds a TM lock on the table in mode 2 for this activity, but differs in its choice of “secondary” lock, using an SK enqueue in mode 6 rather than an OD enqueue. Unlike the coalesce command the shrink space command restricts the undo generated so far to a single undo segment – which could cause some disruptive side effects if other long running jobs are generating undo at the same time.
Summary of “phase 3” coming soon.