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authorTom Lane2007-10-27 05:45:43 +0000
committerTom Lane2007-10-27 05:45:43 +0000
commit834ddc6272943ed7075cbca9646fdacb3598a93d (patch)
tree4603483b26ce5210c7d52dda88acf3776f502f4f /doc/FAQ_IRIX
parent5b5a70aedf133d847d92429e336b06a5fb4c5a2a (diff)
Avoid considering both sort directions as equally useful for merging.
This doubles the planning workload for mergejoins while not actually accomplishing much. The only useful case is where one of the directions matches the query's ORDER BY request; therefore, put a thumb on the scales in that direction, and otherwise arbitrarily consider only the ASC direction. (This is a lot easier now than it would've been before 8.3, since we have more semantic knowledge embedded in PathKeys now.)
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