Partition Stats

It’s possible to spend ages talking about the best ways of collecting, or creating, statistics on partitioned tables.

The possible strategies for maintaining partitioned tables, (exchange partition, split partition, drop partition etc.) the types of partitioning available, and the way that the optimizer plays with the stats as you do so, have kept changing over the years, and I’ve got a large set of examples designed to test what happens to the stats as you do things to the table – but it’s impossible to keep it up to date.

Doug Burns is writing a series of articles about the trials, tribulations, and successes about partitioned tables and statistics. The series was well worth reading and will give you an insight into the problems you may have to address, so I’ve produced a catalogue to make it easy to visit the individual chapters in order.  Make sure you also read the comments and related links.

• Part 1 – In which we see a simple example and do a default stats collection
• Part 2 – In which we consider Global Stats
• Part 3 – In which subpartitions and aggregation cause problems
• Part 4 – In which our hero fights his way through stats aggregation woes
• Part 5 – In which we encounter a partition exchange
• Part 6a – In which we start to use dbms_stats.copy_table_stats()
• Part 6b – In which we see how reputable individuals handle their mistakes
• Part 6c – In which we hear about 10.2.0.5 and lots of bugs
• Part 6d – In which we revisit earlier errors and discuss the benefit of discussion
• Part 6e – In which we revisit earlier problem again and talk about a bug.
• Part 7 – Not in the original series, but an interesting (slow) experience in 11g

I thought I’d collate a few other items on partition stats and optimizer behaviour – mainly from Randolf Geist’s blog:

• March 2007: Subpartitions and Optimizer Stats
• April 2008: (a) Subpartition Pruning
• April 2008: (b) Exchange Partition and Aggregated Stats
• Mar 2009: (a) Partition Oddities and 10.2.0.4 bug
• Mar 2009: (b) List partitions
• June 2009 Dynamic Sampling and partitioned tables
• Jan 2012 Incremental partition statistics

And one from Kerry Osbourne – which lists a new granularity option, and a patch for 10.2.0.4

• Feb 2009: Maintaining statistics on a large partitioned table.  (See also Metalink Doc ID: 6526370.8)

A couple (as pdf files) from David Kurtz, with a particular view to optimising Peoplesoft.

• Gathering aggregated stats on partitioned objects in 10g
• Gathering aggregated stats on partitioned object in 11gR2

And an investigation into an oddity with the optimizer when using partitioned indexes

• Feb 2011: Jokes of the CBO with local indexes (10.2.0.4, 11.1.0.7)