HashAggregate
Short Description
The HashAggregate node builds a hash table to group data
Detailed Description​
Unlike the GroupAggregate node, HashAggregate does not require pre-sorted input as it builds a hash table (or a number of hash tables) to group data. This node can be seen in GROUP BY operations. HashAggregate operations can consume large amounts of memory as they build the hash table(s) and the output is in no particular order.
Additional Links​
- PostgreSQL Documentation - Using Explain
- pgAnalyze - Explain
- eTutorials - Understanding How PostgreSQL Executes a Query
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