Minor Description
This JIRA is to disable two level of maps for final hash aggregation by default. The feature was introduced in #32242 and we found it can lead to query performance regression when the final aggregation gets rows with a lot of distinct keys. The 1st level hash map is full so a lot of rows will waste the 1st hash map lookup and inserted into 2nd hash map. This feature still benefits query with not so many distinct keys though, so introducing a config to allow query to enable the feature when seeing benefit.
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