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HASH GROUP BY

Short Description

Operation hashing a set of rows into groups for a query with a GROUP BY clause.

Detailed Description​

HASH GROUP BY creates an in memory hash table to bucket group by entries together. This is a very fast method of grouping unless you start spilling to disc. Look at TEMPSEG_SIZE in the V$SQL_WORKAREA_ACTIVE view for your session to see current usage.

Further Reading​

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