[IMPALA-12088] Make the predicate pushdown skipping improvement work with the count(*) query rewrite improvement

• Type: Sub-task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Frontend
• Labels: impala-iceberg performance
• Epic Color: ghx-label-11
• Assignee: Unassigned
• Reporter: Gabor Kaszab
• Created: 24/Apr/23 12:32
• Updated: 24/Jul/23 15:18

Description

https://issues.apache.org/jira/browse/IMPALA-11802 introduced a query rewrite for count queries on Iceberg tables as a performance improvement. Later on https://issues.apache.org/jira/browse/IMPALA-11701 introduced the capability to skip pushing down predicates to Impala scanners when Iceberg applied it and won't filter any further rows.

This ticket is to make a connection between these 2 improvements: When we skip pushing down predicates and there is no more predicates to push down and this is a count query then let's do the query rewrite from IMPALA-11802.
One difficulty implementing this is that the query rewrite is done in the analysis phase while the predicate pushdown decision is made in the planner phase so might be a bit more complicated than to re-use the rewrite code.