ttOptEstimateStats

The ttOptEstimateStats procedure updates the statistics for the specified table. This procedure estimates statistics by looking at a random sample of the rows in the specified table(s). The sample size is the number of rows specified (if sampleStr has the form 'n ROWS') or a percentage of the total number of rows (if sampleStr has the form 'p PERCENT').

The procedure operates on all tables owned by the current user if tblName is not specified. If the user is the instance administrator, only tables owned by the instance administrator are updated. If the tables are not owned by the user, the user can qualify the table name with their own user name to update stats for the current user.

To determine if your stats are updated, look at the system tables, SYS.COL_STATS and SYS.TBL_STATS, before and after you perform this operation.

Required Privilege

This procedure requires no privilege if the user is the table owner, or if tblName is not specified. This procedure requires the ALTER ANY TABLE privilege if the user is not the table owner.

Usage in TimesTen Scaleout and TimesTen Classic

This procedure is supported in TimesTen Classic.

TimesTen Scaleout applications can call this built-in procedure.

In TimesTen Scaleout, this procedure runs on all elements in the grid.

Related Views

This procedure has these related views.

SYS.GV$OPT_COL_STATS

SYS.V$OPT_COL_STATS

Syntax

ttOptEstimateStats(['tblName'], [invalidate], 'sampleStr')

Parameters

ttOptEstimateStats has these parameters:

Parameter Type Description

Parameter	Type	Description
`tblName`	`TT_CHAR(61)`	Name of an application table. Can include table owner. If `tblName` is an empty string, statistics are estimated for all the current user's tables in the database. Using a synonym to specify a table name is not supported.
`invalidate`	`TT_INTEGER`	0 (no) or 1 (yes). If `invalidate` is 1, all commands that reference the affected tables are automatically prepared again when re-executed, including commands prepared by other users. If `invalidate` is 0, the statistics are not considered to have been modified and existing commands are not reprepared. The `invalidate` parameter is optional and defaults to 0.
`sampleStr`	`TT_VARCHAR (255) NOT NULL`	String of the form '`n` `ROWS`', where `n` is an `INTEGER` greater than zero; or '`p` `PERCENT`', where `p` is a floating point number between 0.0 and 100.0 inclusive.

tblName

TT_CHAR(61)

Name of an application table. Can include table owner. If tblName is an empty string, statistics are estimated for all the current user's tables in the database.

Using a synonym to specify a table name is not supported.

invalidate

TT_INTEGER

0 (no) or 1 (yes). If invalidate is 1, all commands that reference the affected tables are automatically prepared again when re-executed, including commands prepared by other users. If invalidate is 0, the statistics are not considered to have been modified and existing commands are not reprepared.

The invalidate parameter is optional and defaults to 0.

sampleStr

TT_VARCHAR (255) NOT NULL

String of the form 'n ROWS', where n is an INTEGER greater than zero; or 'p PERCENT', where p is a floating point number between 0.0 and 100.0 inclusive.

Result Set

ttOptEstimateStats returns no results.

Examples

CALL ttOptEstimateStats ( 'ACCTS', 1, '5 PERCENT' );

CALL ttOptEstimateStats ( 'ACCTS', 1, '75 ROWS' );

Notes

The TimesTen statistics include the number of rows in each table, the number of unique values in each column, and the minimum and maximum values in each column. TimesTen assumes a uniform distribution of column values.
This procedure only runs faster than ttOptUpdateStats when you sample less than 50 percent of the rows in the table.
Estimates are not computed on columns that are longer than 2,048 bytes, and statistics for these columns are not updated. To update statistics on columns longer than 2,048 bytes, use the ttOptUpdateStats built-in procedure. (For varying length columns, this procedure updates statistics only if the column has a maximum length of 2,048 bytes or less.)
If a very small value is chosen for the sampleStr parameter, this procedure runs quickly but may result in suboptimal execution plans. For "good" distributions of data, a 10 percent selection is a good choice for computing statistics quickly without sacrificing plan accuracy. If the number of rows specified is large or the table in question is small, to improve performance TimesTen computes exact statistics on all columns that have a length of 2,048 bytes or less. For example, the only difference between
ttOptEstimateStats ('ACCTS', 1, '100 PERCENT' )
and
ttOptUpdateStats( 'ACCTS', 1 )
is that the former does not compute statistics for long columns.
The statistics are stored in the TBL_STATS and COL_STATS system tables.
For performance reasons, ttOptEstimateStats does not hold a lock on tables or rows when computing statistics. However, it holds a lock on the TimesTen system tables. Computing statistics can still slow performance. Estimating statistics generally provides better performance than computing exact statistics.
If you estimate or update statistics with an empty table list, statistics on system tables are updated also, if you have privileges to update the system tables.