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Preface

Virtuoso Functions Guide

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Aggregate Functions
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Functions Index

SYS_DB_STAT

gathers common statistical information about the database.
SYS_DB_STAT (in pcnt integer, in ignore_vdb integer);
Description

The SYS_DB_STAT procedure gathers common information about the whole Virtuoso database, including attached remote tables. It traverses each table and populates the SYS_COL_STAT table with data collected. SYS_DB_STAT can be used in random mode when not all rows of the tables are used to gather statistics of the database.

SYS_DB_STAT gathers the following information for each column, COL, traversed in the database:

If remote tables are not ignored and random traversal is switched on then SYS_DB_STAT reads the first 1000 rows and restores statistics by the first 1000 rows of table.

Parameters
pcnt – Rate that affects percentage of database coverage. If it is less than 5 then this parameter is ignored. If pcnt more than 500 then SYS_DB_STAT acts as if the parameter was equal to 500. There is no accurate conformity between pcnt and percentage of databse coverage, but it is known that 5 usually means 10 percent of covarage and 500 means almost 100 percent.
ignore_vdb – By default SYS_DB_STAT does not analyze the remote tables. To allow statistics gathering over linked tables, set this parameter to zero. Remote tables can be very large or access to them can be very slow or both. If this parameter is set to zero and pcnt is zero, SYS_DB_STAT could take a lot of time.
Return Types

None.

See Also

sys_stat_histogram

sys_stat_analyze