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mi_istats_set2sval()

The mi_istats_set2sval() function stores the second-smallest index-key value in the statistics descriptor.

Syntax

void mi_istats_set2sval(MI_AM_ISTATS_DESC *istatsDesc,
   void *2sval)
IstatsDesc
points to the statistics descriptor.
2sval
points to the second-smallest key value in the index.

Usage

To determine the minimum value for an index key while it evaluates a query plan, the optimizer looks at the colmin value for the key column in the syscolumns system catalog table. The colmin column holds a 4-byte integer that represents the second-smallest key value in the index. The optimizer assesses the second-smallest key value to avoid the distortion that an abnormally low value can cause to the data distribution.

The am_stats purpose function can provide the second-largest value for each key. After storing the value in memory, pass it by reference with the mi_istats_set2sval() function. The database server places the first four bytes that begin at address 2sval as an integer value in the colmin column.

Return Values

None

Related Topics

See the description of function mi_istats_set2lval().

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