8f59f6b9c0
For relatively simple expressions (say, "x + 1" or "x > 0"), plpgsql's management overhead exceeds the cost of evaluating the expression. This patch substantially improves that situation, providing roughly 2X speedup for such trivial expressions. First, add infrastructure in the plancache to allow fast re-validation of cached plans that contain no table access, and hence need no locks. Teach plpgsql to use this infrastructure for expressions that it's already deemed "simple" (which in particular will never contain table references). The fast path still requires checking that search_path hasn't changed, so provide a fast path for OverrideSearchPathMatchesCurrent by counting changes that have occurred to the active search path in the current session. This is simplistic but seems enough for now, seeing that PushOverrideSearchPath is not used in any performance-critical cases. Second, manage the refcounts on simple expressions' cached plans using a transaction-lifespan resource owner, so that we only need to take and release an expression's refcount once per transaction not once per expression evaluation. The management of this resource owner exactly parallels the existing management of plpgsql's simple-expression EState. Add some regression tests covering this area, in particular verifying that expression caching doesn't break semantics for search_path changes. Patch by me, but it owes something to previous work by Amit Langote, who recognized that getting rid of plancache-related overhead would be a useful thing to do here. Also thanks to Andres Freund for review. Discussion: https://postgr.es/m/CAFj8pRDRVfLdAxsWeVLzCAbkLFZhW549K+67tpOc-faC8uH8zw@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: 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/.