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Up to now we've just searched the placeholder_list when we want to find the PlaceHolderInfo with a given ID. While there's no evidence of that being a problem in the field, an upcoming patch will add find_placeholder_info() calls in build_joinrel_tlist(), which seems likely to make it more of an issue: a joinrel emitting lots of PlaceHolderVars would incur O(N^2) cost, and we might be building a lot of joinrels in complex queries. Hence, add an array that can be indexed directly by phid to make the lookups constant-time. Discussion: https://postgr.es/m/1405792.1660677844@sss.pgh.pa.us
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/.