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preprocess_expression skips flatten_join_alias_vars for TABLESAMPLE clauses, on the assumption that they cannot contain Vars of the current query level. That's not true once a LATERAL subquery containing a sampled relation has been pulled up: the relation's TABLESAMPLE clause then becomes a lateral reference of this level, and if it referred to a join alias Var, that Var is left unexpanded. extract_lateral_references then pulls the join alias Var out as a lateral reference and fails with "no relation entry for relid N". To fix, treat such clauses like lateral function and VALUES RTEs: introduce EXPRKIND_TABLESAMPLE_LATERAL, used for the TABLESAMPLE clause of a lateral relation RTE, and keep skipping the alias expansion only for the non-lateral kind. Back-patch to all supported branches, as this dates back to the introduction of TABLESAMPLE. Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Ewan Young <kdbase.hack@gmail.com> Reviewed-by: Ayush Tiwari <ayushtiwari.slg01@gmail.com> Discussion: https://postgr.es/m/CAMbWs4834TwOtyyycyvja3MuOBkfpXy3dFAL0zt_vcM1KtqV-Q@mail.gmail.com Backpatch-through: 14
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/.