I have a query which was going out of spool and once i dropped few stats from a table it ran in a minute.In query i have joining on
COSTCNTR_HIER_ID and where condition for "COSTCNTR_CODE" = 'NULL'
Howcome droppping below improved the performance because COSTCNTR_CODE is in filter condition.All stats were refreshed prior to drop.
This can happen if you add statistics to a table and they cause a change in the execution plan. As a result, the Optimizer may use now other statistics which are available on this table. If these statistics are stale, the execution plan can become bad.