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The qual pushdown logic assumed that all Vars in a restriction clause must be Vars referencing subquery outputs; but since we introduced LATERAL, it's possible for such a Var to be a lateral reference instead. This led to an assertion failure in debug builds. In a non-debug build, there might be no ill effects (if qual_is_pushdown_safe decided the qual was unsafe anyway), or we could get failures later due to construction of an invalid plan. I've not gone to much length to characterize the possible failures, but at least segfaults in the executor have been observed. Given that this has been busted since 9.3 and it took this long for anybody to notice, I judge that the case isn't worth going to great lengths to optimize. Hence, fix by just teaching qual_is_pushdown_safe that such quals are unsafe to push down, matching the previous behavior when it accidentally didn't fail. Per report from Tom Ellis. Back-patch to all supported branches. Discussion: https://postgr.es/m/20200713175124.GQ8220@cloudinit-builder
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/.