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Some experimentation with examples similar to bug #7539 has convinced me that indxpath.c's original implementation of parameterized-path generation was several bricks shy of a load. In general, if we are relying on a particular outer rel or set of outer rels for a parameterized path, the path should use every indexable join clause that's available from that rel or rels. Any join clauses that get left out of the indexqual will end up getting applied as plain filter quals (qpquals), and that's generally a significant loser compared to having the index AM enforce them. (This is particularly true with btree, which can skip the index scan entirely if it can see that the given indexquals are mutually contradictory.) The original heuristics failed to ensure this, though, and were overly complicated anyway. Rewrite to make the code explicitly identify each useful set of outer rels and then select all applicable join clauses for each one. The one plan that changes in the regression tests is in fact for the better according to the planner's cost estimates. (Note: this is not a correctness issue but just a matter of plan quality. I don't yet know what is going on in bug #7539, but I don't expect this change to fix that.) |
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PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: http://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Changes between all PostgreSQL releases are recorded in the file HISTORY. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.