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inputs is unique or nearly so), make eqjoinsel() clamp the ndistinct estimates to be not more than the estimated number of rows coming from the input relations. This allows the estimate to change in response to the selectivity of restriction conditions on the inputs. This is a pretty narrow patch and maybe we should be more aggressive about similarly clamping ndistinct in other cases; but I'm worried about double-counting the effects of the restriction conditions. However, it seems to help for the case exhibited by Grzegorz Jaskiewicz (antijoin against a small subset of a relation), so let's try this for awhile. |
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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/.