732bfa2448
cost_index's method for estimating per-tuple costs of evaluating filter conditions (a/k/a qpquals) was completely wrong in the presence of derived indexable conditions, such as range conditions derived from a LIKE clause. This was largely masked in common cases as a result of all simple operator clauses having about the same costs, but it could show up in a big way when dealing with functional indexes containing expensive functions, as seen for example in bug #6579 from Istvan Endredy. Rejigger the calculation to give sane answers when the indexquals aren't a subset of the baserestrictinfo list. As a side benefit, we now do the calculation properly for cases involving join clauses (ie, parameterized indexscans), which we always overestimated before. There are still cases where this is an oversimplification, such as clauses that can be dropped because they are implied by a partial index's predicate. But we've never accounted for that in cost estimates before, and I'm not convinced it's worth the cycles to try to do so. |
||
|---|---|---|
| config | ||
| contrib | ||
| doc | ||
| src | ||
| .gitignore | ||
| COPYRIGHT | ||
| GNUmakefile.in | ||
| Makefile | ||
| README | ||
| README.git | ||
| aclocal.m4 | ||
| configure | ||
| configure.in | ||
README
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/.