When cardinality statistics are automatically updated

For the following operations that you perform on a table, Derby automatically creates new statistics or updates existing statistics:

The thread that updates the statistics in the background during query compilation may affect the performance of the user threads. If this causes problems, you can disable automatic updating of statistics by setting the database property derby.storage.indexStats.auto to false.

To diagnose problems with automatic updating of index statistics, an application can set the database property derby.storage.indexStats.log to true. When this property is set, the thread that updates the statistics will write messages to the Derby system log (derby.log) every time it performs a task. You can obtain more detailed logging information by setting the property derby.storage.indexStats.trace, which also lets you specify where the trace output should appear.

See the Java DB Reference Manual for details about these properties.

To remove all statistics in case of problems, call the SYSCS_UTIL.SYSCS_DROP_STATISTICS system procedure. See the Java DB Reference Manual for details about this procedure and about SYSCS_UTIL.SYSCS_COMPRESS_TABLE.

Related concepts
When cardinality statistics go stale