postgres

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Tom Lane 83204e100c Fix contrib/postgres_fdw to handle multiple join conditions properly. The previous coding supposed that it could consider just a single join condition in any one parameterized path for the foreign table. But in reality, the parameterized-path machinery forces all join clauses that are "movable to" the foreign table to be evaluated at that node; including clauses that we might not consider safe to send across. Such cases would result in an Assert failure in an assert-enabled build, and otherwise in sending an unsafe clause to the foreign server, which might result in errors or silently-wrong answers. A lesser problem was that the cost/rowcount estimates generated for the parameterized path failed to account for any additional join quals that get assigned to the scan. To fix, rewrite postgresGetForeignPaths so that it correctly collects all the movable quals for any one outer relation when generating parameterized paths; we'll now generate just one path per outer relation not one per join qual. Also fix bogus assumptions in postgresGetForeignPlan and estimate_path_cost_size that only safe-to-send join quals will be presented. Based on complaint from Etsuro Fujita that the path costs were being miscalculated, though this is significantly different from his proposed patch.	12 years ago
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postgres_fdw.out	Fix contrib/postgres_fdw to handle multiple join conditions properly.	12 years ago

Tom Lane 83204e100c Fix contrib/postgres_fdw to handle multiple join conditions properly.

The previous coding supposed that it could consider just a single join
condition in any one parameterized path for the foreign table.  But in
reality, the parameterized-path machinery forces all join clauses that are
"movable to" the foreign table to be evaluated at that node; including
clauses that we might not consider safe to send across.  Such cases would
result in an Assert failure in an assert-enabled build, and otherwise in
sending an unsafe clause to the foreign server, which might result in
errors or silently-wrong answers.  A lesser problem was that the
cost/rowcount estimates generated for the parameterized path failed to
account for any additional join quals that get assigned to the scan.

To fix, rewrite postgresGetForeignPaths so that it correctly collects all
the movable quals for any one outer relation when generating parameterized
paths; we'll now generate just one path per outer relation not one per join
qual.  Also fix bogus assumptions in postgresGetForeignPlan and
estimate_path_cost_size that only safe-to-send join quals will be
presented.

Based on complaint from Etsuro Fujita that the path costs were being
miscalculated, though this is significantly different from his proposed
patch.

12 years ago

postgres_fdw.out

Fix contrib/postgres_fdw to handle multiple join conditions properly.

12 years ago