Granularity 'APPROX_GLOBAL AND PARTITION'
The patchset 11.1.0.7 introduces in the package DBMS_STATS a new value for the parameter GRANULARITY. The description provided by the development team in $ORACLE_HOME/rdbms/admin/dbmsstat.sql is the...
View ArticleDoes CREATE INDEX Gather Global Statistics?
You can add the COMPUTE STATISTICS clause to the CREATE INDEX statement. It instructs the SQL statement to gather and store index statistics in the data dictionary, while creating the index. This is...
View ArticleChallenges and Chances of the 11g Query Optimizer
Challenges and Chances of the 11g Query Optimizer is the name of a presentation I gave at several events (e.g. Trivadis Performance Days, Oracle OpenWorld, DOAG Konferenz, UKOUG Conference) throughout...
View ArticleExtension Bypassed Because of Missing Histogram
Today, while tuning a fairly complex query experiencing wrong cardinality estimates, I noticed something I was not aware of. Hence, I thought to write this short post to illustrate how to reproduce the...
View ArticleRestrict the query optimizer through OPTIMIZER_FEATURES_ENABLE and...
To make upgrades easier, I regularly see people considering disabling query optimizer features by setting the OPTIMIZER_FEATURES_ENABLE initialization parameter to a non-default value. My general...
View ArticleAlso Extensions Created Because of SQL Plan Directives Can Invalidate Packages
UPDATE 2015-12-18: As metioned by Bryn Llewellyn in this tweet, the invalidation I describe below is caused by bug 19450314. A patch for it is available here for several releases (e.g. it is available...
View ArticleAlso Extensions Created Because of SQL Plan Directives Can Invalidate...
In a previous post I described a situation where the creation of an extension, independently of whether it’s carried out manually by a person or automatically by the database engine, can lead to the...
View ArticleSPD State Does Not Change If Adaptive Statistics Are Disabled
The aim of this post is to point out an issue (bug?) that I recently discovered. But, before talking about it, I need to go through a rather long introduction about the state of SQL plan directive...
View ArticleCDB Views and Query Optimizer Cardinality Estimations
Today I faced a performance problem caused by a bad cardinality estimation involving a CDB view in a 12.1.0.2 multitenant environment. While solving the problem I did a number of observations that I...
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