[IMPALA-12383] Aggregation with num_nodes=1 and limit returns too many rows

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 4.1.0
• Fix Version/s: Impala 4.3.0
• Component/s: Backend, Frontend
• Target Version: Impala 4.1.3
• Epic Color: ghx-label-1
• Assignee: Michael Smith
• Reporter: Michael Smith
• Created: 17/Aug/23 23:29
• Updated: 10/Sep/24 23:21
• Resolved: 11/Sep/23 18:01

Description

With set num_nodes=1 to select SingleNodePlanner, aggregations return too many rows:

> select distinct l_orderkey from tpch.lineitem limit 10;
...
Fetched 16 row(s) in 0.12s
> select ss_cdemo_sk from tpcds.store_sales group by ss_cdemo_sk limit 3;
...
Fetched 7 row(s) in 0.14s

This looks like it's caused by changes in IMPALA-2581, which attempts to push down limits to pre-aggregation. In SingleNodePlanner, there is no pre-aggregation, which the patch appears to have failed to account for.

Issue Links

• is caused by: IMPALA-2581 Push down LIMIT past DISTINCT