Comments on: Index Efficiency 3

By: ASSM wreck « Oracle Scratchpad

ASSM wreck « Oracle Scratchpad — Wed, 30 Mar 2011 21:22:17 +0000

[...] is doing something similar to the model then it’s worth checking the related indexes (see my index efficiency note) to see if any of them are displaying the same problem as this test case. If they are you may want [...]

By: Statistics problem « Oracle Scratchpad

Statistics problem « Oracle Scratchpad — Mon, 22 Mar 2010 06:59:31 +0000

[...] this note on my website – now corrected and enhanced in the script catalog – about how to use the sys_op_lbid() function to do a detailed check on [...]

By: Index Explosion « Oracle Scratchpad

Index Explosion « Oracle Scratchpad — Wed, 10 Mar 2010 22:48:13 +0000

[...] you run something like my “index efficiency” code to check how well each block in the index is used, you may find something like [...]

By: Jonathan Lewis

Jonathan Lewis — Fri, 05 Mar 2010 10:14:07 +0000

Flado,

Casting my mind back nearly seven years – I’ve got no idea. As I pointed out at the top of this note, and on the catalog page, these are just quick hacks I put together and they’re not intended to be polished, bullet-proof code.

I’ll take a guess that when I wrote the introductory statement I started with a query to pull back the columns I needed in the right order, checked it was working, then did the max(decode()) trick and forgot to eliminate the “order by”.

(Of course, if Oracle had considered that an error seven years ago, it wouldn’t be here today).

Prompted by the thought of a seven-year-old hack, I’ve just had to ask myself what it would do if you created an index with a function-based column – without testing it I don’t think I’d know whether or not it would still work.

By: Flado

Flado — Thu, 04 Mar 2010 12:51:32 +0000

Jonathan,

What’s the point of “order by column_position” in lines 87-88?
I’m actually quite impressed that Oracle politely ignores attempts to order a single row – I didn’t know that.

Cheers!
Flado

By: Simple scripts « Oracle Scratchpad

Simple scripts « Oracle Scratchpad — Thu, 04 Mar 2010 05:20:58 +0000

[...] a data dictionary scan for simple B-tree indexes that may be unreasonably large for the data held Index Leaf Block scanner: a labour-intensive analysis of leaf block usage for a simple B-tree [...]

By: Index Efficiency 3 « Oracle Scratchpad

Index Efficiency 3 « Oracle Scratchpad — Wed, 03 Mar 2010 21:21:28 +0000

[...] thought than just the simple “it’s two / four times the size”- and this is what the script index_efficiency_3.sql is about. Given the schema, table, and index name, it produces a report which tells you about the [...]