hadoop-hive-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Created: (HIVE-746) constant folding
Date Tue, 11 Aug 2009 02:11:14 GMT
constant folding

                 Key: HIVE-746
                 URL: https://issues.apache.org/jira/browse/HIVE-746
             Project: Hadoop Hive
          Issue Type: New Feature
          Components: Query Processor
            Reporter: Namit Jain

The constants are not folded at compile time:

for eg:

select 1+2 from src

will evaluate 1+2 for every row.

This becomes more interesting for scenarios like:

select unix_timestamp() from src;

The UDF should be evaluated only once, and the same value should be returned. However, currently,
we mark it as non-deterministic and evaluate it for every row.
This can have bad side-effects on partition pruning etc.

In MySQL, the same value is generated independent of the time taken for the query.

This message is automatically generated by JIRA.
You can reply to this email to add a comment to the issue online.

View raw message