[CALCITE-404] MergeProjectRule should not construct RexPrograms for simple mappings

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.9.1-incubating
• Assignee: Julian Hyde
• Reporter: Julian Hyde
• Created: 05/Sep/14 23:07
• Updated: 18/Oct/14 22:36
• Resolved: 06/Sep/14 00:09

Description

MergeProjectRule should not construct RexPrograms when it is dealing with projections that are simple mappings or permutations. It can combine the mappings using less computation and memory.

Further, if either of the projects is the identity, MergeProjectRule should do nothing; it should let RemoveTrivialProjectRule deal with it.

This should reduce the amount of memory required for complex planning, in particular when there are large joins and many calls to SwapJoinRule. OPTIQ-62 is a better but more complex solution to the same issue.

Issue Links

• is related to: CALCITE-62 Allow a RelNode in a RelSet to return columns in permuted order