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Cumulative stats kinds gain the capability to write additional per-entry data when flushing the stats at shutdown, and read this data when loading back the stats at startup. This can be fit for example in the case of variable-length data (like normalized query strings), so as it becomes possible to link the shared memory stats entries to data that is stored in a different area, like a DSA segment. Three new optional callbacks are added to PgStat_KindInfo, available to variable-numbered stats kinds: * to_serialized_data: writes auxiliary data for an entry. * from_serialized_data: reads auxiliary data for an entry. * finish: performs actions after read/write/discard operations. This is invoked after processing all the entries of a kind, allowing extensions to close file handles and clean up resources. Stats kinds have the option to store this data in the existing pgstats file, but can as well store it in one or more additional files whose names can be built upon the entry keys. The new serialized callbacks are called once an entry key is read or written from the main stats file. A file descriptor to the main pgstats file is available in the arguments of the callbacks. Author: Sami Imseih <samimseih@gmail.com> Co-authored-by: Michael Paquier <michael@paquier.xyz> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Discussion: https://postgr.es/m/CAA5RZ0s9SDOu+Z6veoJCHWk+kDeTktAtC-KY9fQ9Z6BJdDUirQ@mail.gmail.com
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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.