[SPARK-29650] Discard a NULL constant in LIMIT

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Invalid
• Affects Version/s: 3.0.0
• Component/s: SQL
• Assignee: Unassigned
• Reporter: Takeshi Yamamuro
• Created: 30/Oct/19 06:53
• Updated: 01/Dec/19 22:24
• Resolved: 01/Dec/19 22:24

Description

In PostgreSQL, a NULL constant is accepted in LIMIT and its just ignored.

But, in spark, it throws an exception below;

select * from int8_tbl limit (case when random() < 0.5 then bigint(null) end);

org.apache.spark.sql.AnalysisException
The limit expression must evaluate to a constant value, but got CASE WHEN (`_nondeterministic` < CAST(0.5BD AS DOUBLE)) THEN CAST(NULL AS BIGINT) END;