Prevent automatic indexing from creating worse queries
------------------------------------------------------
Key: HIVE-2081
URL: https://issues.apache.org/jira/browse/HIVE-2081
Project: Hive
Issue Type: Improvement
Components: Indexing
Affects Versions: 0.8.0
Reporter: Russell Melick
We want to make sure that automatically using indexes doesn't make the query
worse. For example, after scanning the index table, it might still need to
scan the whole base table. In this case, we would much rather just kill the
index job and go back and scan the whole base table.
This can be done by adding a conditional task and a backup task. You can detect
whether the index is good or not by monitoring the index job's number of input
records and number of output records, and comparing them. As an initial
example, if the ratio is >50, do not use the index, and go back to scanning the
whole base table.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
