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Base de données relationnelle
e3ffd05b02
We should be willing to cross-join two small relations if that allows us to use an inner indexscan on a large relation (that is, the potential indexqual for the large table requires both smaller relations). This worked in simple cases but fell apart as soon as there was a join clause to a fourth relation, because the existence of any two-relation join clause caused the planner to not consider clauseless joins between other base relations. The added regression test shows an example case adapted from a recent complaint from Benoit Delbosc. Adjust have_relevant_joinclause, have_relevant_eclass_joinclause, and has_relevant_eclass_joinclause to consider that a join clause mentioning three or more relations is sufficient grounds for joining any subset of those relations, even if we have to do so via a cartesian join. Since such clauses are relatively uncommon, this shouldn't affect planning speed on typical queries; in fact it should help a bit, because the latter two functions in particular get significantly simpler. Although this is arguably a bug fix, I'm not going to risk back-patching it, since it might have currently-unforeseen consequences. |
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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/.