[HIVE-72] wrong results if partition pruning not strict and no mep-reduce job needed

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.3.0
• Component/s: Query Processor
• Hadoop Flags: Reviewed
• Assignee: Namit Jain
• Reporter: Namit Jain
• Created: 18/Nov/08 22:22
• Updated: 17/Dec/11 00:08
• Resolved: 20/Nov/08 22:29

Description

Suppose T is a partitioned table on ds, where ds is a string column, the following queries:

SELECT a.* FROM T a WHERE a.ds=2008-09-08 LIMIT 1;
SELECT a.* FROM T a WHERE a.ds=2008-11-10 LIMIT 1;

return the first row from the first partition.

This is because of the typecast to double.

for a.ds=2008-01-01 or anything (a.ds=1),

evaluate (Double, Double) is invoked at partition pruning.

Since '2008-11-01' is not a valid double, it is converted to a null, and therefore the result of pruning returns null (unknown) - not FALSE.
All unknowns are also accepted, therefore all partitions are accepted which explains this behavior.

filter is not invoked since it is a select * query, so map-reduce job is started.
We just turn off this optimization if pruning indicates that there can be unknown partitions.