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join_is_legal() needs to reject forming certain outer joins in cases where that would lead the planner down a blind alley. However, it mistakenly supposed that the way to handle full joins was to treat them as applying the same constraints as for left joins, only to both sides. That doesn't work, as shown in bug #15741 from Anthony Skorski: given a lateral reference out of a join that's fully enclosed by a full join, the code would fail to believe that any join ordering is legal, resulting in errors like "failed to build any N-way joins". However, we don't really need to consider full joins at all for this purpose, because we effectively force them to be evaluated in syntactic order, and that order is always legal for lateral references. Hence, get rid of this broken logic for full joins and just ignore them instead. This seems to have been an oversight in commit 7e19db0c0. Back-patch to all supported branches, as that was. Discussion: https://postgr.es/m/15741-276f1f464b3f40eb@postgresql.org
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: https://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 https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.