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/.
Tom Lane
authored
So far as I can tell, it is no longer possible for this heuristic to do anything useful, because the new weaker definition of have_relevant_joinclause means that any relation with a joinclause must be considered joinable to at least one other relation. It would still be possible for the code block to be entered, for example if there are join order restrictions that prevent any join of the current level from being formed; but in that case it's just a waste of cycles to attempt to form cartesian joins, since the restrictions will still apply. Furthermore, IMO the existence of this code path can mask bugs elsewhere; we would have noticed the problem with cartesian joins a lot sooner if this code hadn't compensated for it in the simplest case. Accordingly, let's remove it and see what happens. I'm committing this separately from the prerequisite changes in have_relevant_joinclause, just to make the question easier to revisit if there is some fault in my logic.
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