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The previous patch made addition of new GUCs cheap, but other GUC operations aren't improved and indeed get a bit slower, because hash_seq_search() is slower than just scanning a pointer array. However, most performance-critical GUC operations only need to touch a relatively small fraction of the GUCs; especially so for AtEOXact_GUC(). We can improve matters at the cost of a bit more space by adding dlist or slist links to the GUC data structures. This patch invents lists that track (1) all GUCs with non-default "source"; (2) all GUCs with nonempty state stack (implying they've been changed in the current transaction); (3) all GUCs due for reporting to the client. All of guc.c's performance-critical cases can make use of one or another of these lists to avoid searching the whole hash table. In particular, the stack list means that transaction end doesn't take time proportional to the number of GUCs, but only to the number changed in the current transaction. Discussion: https://postgr.es/m/2982579.1662416866@sss.pgh.pa.us |
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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/.