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50e17ad28 increased the size of ExprEvalStep from 64 bytes up to 88 bytes. Lots of effort was spent during the development of the current expression evaluation code to make an instance of this struct as small as possible. Making this struct larger than needed reduces CPU cache efficiency during expression evaluation which causes noticeable slowdowns during query execution. In order to reduce the size of the struct, here we remove the fn_addr field. The values from this field can be obtained via fcinfo, just with some extra pointer dereferencing. The extra indirection does not seem to cause any noticeable slowdowns. Various other fields have been moved into the ScalarArrayOpExprHashTable struct. These fields are only used when the ScalarArrayOpExprHashTable pointer has already been dereferenced, so no additional pointer dereferences occur for these. Here we also make hash_fcinfo_data the last field in ScalarArrayOpExprHashTable so that we can avoid a further pointer dereference to get the FunctionCallInfoBaseData. This also saves a call to palloc(). 50e17ad28 was added in 14, but it's too late to adjust the size of the ExprEvalStep in that version, so here we just backpatch to 15, which is currently in beta. Author: Andres Freund, David Rowley Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de Backpatch-through: 15
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/.