Name
SYS_DB_STAT — gathers common statistical information about the database.
Synopsis
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:
| SYS_COL_STAT - SQL command |
| CS_N_DISTINCT - count (distinct XXX) |
| CS_MIN - min (XXX) |
| CS_MAX - max (XXX) |
| CS_AVG_LEN - avg (raw_length (XXX)) |
| CS_N_VALUES - count (XXX) |
| CS_N_ROWS - count (XXX) |
Parameters
pcnt
Rate that affects percentage of database coverage. Zero means that the whole database is read. The default is 5, for a random sample of approximately 5 percent of each table.
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 will read the remote tables from start to end which may take very long. If pcnt is non-zero, this function will use its knowledge of the remote DBMS to get statistics in a DBMS specific manner if the DBMS is supported. See sys_stat_vdb_mappers table.
Return Types
None.