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b9896198cf
genericcostestimate() and friends used the cost of the entire indexqual expressions as the charge for initial evaluation of indexscan arguments. But of course the index column is not evaluated, only the other side of the qual expression, so this was a bad overestimate if the index column was an expensive expression. To fix, refactor the logic in this area so that there's a single routine charged with deconstructing index quals and figuring out what is the index column and what is the comparison expression. This is more or less free in the case of btree indexes, since btcostestimate() was doing equivalent deconstruction already. It probably adds a bit of new overhead in the cases of other index types, but not a lot. (In the case of GIN I think I saved something by getting rid of code that wasn't aware that the index column associations were already available "for free".) Per recent gripe from Jeff Janes. Arguably this is a bug fix, but I'm hesitant to back-patch because of the possibility of destabilizing plan choices that people may be happy with. |
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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. 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/.