The mi_istats_set2lval() accessor function

Syntax

void mi_istats_set2lval(MI_AM_ISTATS_DESC *istatsDesc,
   void *2lval)

istatsDesc

Points to the statistics descriptor.

2lval

Points to the second-largest key value in the index.

Usage

To determine the maximum value for an index key while it evaluates a query plan, the optimizer looks at the colmax value for the key column in the syscolumns system catalog table. The colmax column holds a 4-byte integer that represents the second-largest key value in the index. The optimizer assesses the second-largest key value to avoid the distortion that an excessive 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_set2lval() function. The database server places the first four bytes that begin at address 2lval as an integer value in the colmax column.

Return values

None