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A test case provided by Mathieu Fenniak shows that the initial search for the target catcache in CatalogCacheIdInvalidate consumes a very significant amount of overhead in cases where cache invalidation is triggered but has little useful work to do. There is no good reason for that search to exist at all, as the index array maintained by syscache.c allows direct lookup of the catcache from its ID. We just need a frontend function in syscache.c, matching the division of labor for most other cache-accessing operations. While there's more that can be done in this area, this patch alone reduces the runtime of Mathieu's example by 2X. We can hope that it offers some useful benefit in other cases too, although usually cache invalidation overhead is not such a striking fraction of the total runtime. Back-patch to 9.4 where logical decoding was introduced. It might be worth going further back, but presently the only case we know of where cache invalidation is really a significant burden is in logical decoding. Also, older branches have fewer catcaches, reducing the possible benefit. (Note: although this nominally changes catcache's API, we have always documented CatalogCacheIdInvalidate as a private function, so I would have little sympathy for an external module calling it directly. So backpatching should be fine.) Discussion: https://postgr.es/m/CAHoiPjzea6N0zuCi=+f9v_j94nfsy6y8SU7-=bp4=7qw6_i=Rg@mail.gmail.com |
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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: http://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 http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.