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Rev 2762: MWL#68 Subquery optimization: Efficient NOT IN execution with NULLs in file:///home/tsk/mprog/src/5.3-mwl68/


At file:///home/tsk/mprog/src/5.3-mwl68/

revno: 2762
revision-id: timour@xxxxxxxxxxxx-20100219215557-g1uohrur8bopfv7n
parent: psergey@xxxxxxxxxxxx-20100217215941-5uxponk64p55xg4a
committer: timour@xxxxxxxxxxxx
branch nick: 5.3-mwl68
timestamp: Fri 2010-02-19 23:55:57 +0200
  MWL#68 Subquery optimization: Efficient NOT IN execution with NULLs
  This patch implements correct NULL semantics for materialized subquery execution.
  The implementation has the following properties and main limitations:
  - It passes all query result tests, but fails a number of EXPLAIN tests because of
    changed plans.
  - The EXPLAIN output for partial matching is not decided yet.
  - It works only when all necessary indexes fit into main memory. Notice that these
    are not the general B-tree/Hash indexes, but instead much more compact ones,
    therefore this limitation may not be a problem in many practical cases.
  - It doesn't contain specialized tests.
  - In several places the implementation uses methods that are modified copies of
    other similar methods. These cases need to be refactored to avoid code duplication.
  - Add a test if the predicate is top-level just before deciding on partial matching.
    If it is top-level, use a more efficient exec method (index lookup).
  - Add sorting of indexes according to their selectivity. The code is almost there.
  - Needs more comments, and to sync existing ones with the implementation.
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