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| -rw-r--r-- | doc/TODO | 20 |
1 files changed, 16 insertions, 4 deletions
@@ -2,7 +2,7 @@ TODO list for PostgreSQL ======================== Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) -Last updated: Wed Jan 19 09:17:41 EST 2005 +Last updated: Sat Jan 22 15:05:08 EST 2005 The most recent version of this document can be viewed at the PostgreSQL web site, http://www.PostgreSQL.org. @@ -246,7 +246,7 @@ Indexes * Use indexes for MIN() and MAX() MIN/MAX queries can already be rewritten as SELECT col FROM tab ORDER - BY col {DESC} LIMIT 1. Completing this item involves making this + BY col {DESC} LIMIT 1. Completing this item involves doing this transformation automatically. * Use index to restrict rows returned by multi-key index when used with @@ -684,8 +684,20 @@ Cache We could use a fixed row count and a +/- count to follow MVCC visibility rules, or a single cached value could be used and - invalidated if anyone modifies the table. - + invalidated if anyone modifies the table. Another idea is to + get a count directly from a unique index, but for this to be + faster than a sequential scan it must avoid access to the heap + to obtain tuple visibility information. + +* Allow data to be pulled directly from indexes + + Currently indexes do not have enough tuple tuple visibility + information to allow data to be pulled from the index without + also accessing the heap. One way to allow this is to set a bit + to index tuples to indicate if a tuple is currently visible to + all transactions when the first valid heap lookup happens. This + bit would have to be cleared when a heap tuple is expired. + * Consider automatic caching of queries at various levels: o Parsed query tree o Query execute plan |