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authorTom Lane <tgl@sss.pgh.pa.us>2013-07-07 22:37:28 -0400
committerTom Lane <tgl@sss.pgh.pa.us>2013-07-07 22:37:28 -0400
commit8b6191e1d5e48d521c42d5f6bdbf8413874f7206 (patch)
tree495f2ad69cd0ee8d5533fbc83d7ae1338ab45970 /src/tutorial/funcs.c
parent95b4e8761e3aac9d27c59b89eb3ca5c90d93f9da (diff)
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Fix planning of parameterized appendrel paths with expensive join quals.
The code in set_append_rel_pathlist() for building parameterized paths for append relations (inheritance and UNION ALL combinations) supposed that the cheapest regular path for a child relation would still be cheapest when reparameterized. Which might not be the case, particularly if the added join conditions are expensive to compute, as in a recent example from Jeff Janes. Fix it to compare child path costs *after* reparameterizing. We can short-circuit that if the cheapest pre-existing path is already parameterized correctly, which seems likely to be true often enough to be worth checking for. Back-patch to 9.2 where parameterized paths were introduced.
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