[IMPALA-7878] Bad SQL generated by compute incremental stats

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Frontend
• Epic Color: ghx-label-9
• Assignee: Fang-Yu Rao
• Reporter: Pooja Nilangekar
• Created: 21/Nov/18 19:39
• Updated: 09/Apr/19 23:36

Description

Computing incremental stats on partitions generates bad sql for instance:
For a table foo partitioned by column bar, the compute stats statement:

compute incremental stats foo partition (bar = 1); 

would generate the following query:

SELECT COUNT(*), month FROM foo WHERE (bar=1) GROUP BY bar;

If this were to be rewritten as follows, it would produce fewer fragments and hence also reduce query memory by avoiding a hash aggregation node.

SELECT COUNT(*), 1 FROM foo WHERE bar=1;