5d56d07ca3
nodeRecursiveunion.c makes use of two tuplestores and, until now, would delete and recreate one of these tuplestores after every recursive iteration. Here we adjust that behavior and instead reuse one of the existing tuplestores and just empty it of all tuples using tuplestore_clear(). This saves some free/malloc roundtrips and has shown a 25-30% performance improvement for queries that perform very little work between recursive iterations. This also paves the way to add some EXPLAIN ANALYZE telemetry output for recursive common table expressions, similar to what was done in 1eff8279d and 95d6e9af0. Previously calling tuplestore_end() would have caused the maximum storage space used to be lost. Reviewed-by: Tatsuo Ishii Discussion: https://postgr.es/m/CAApHDvr9yW0YRiK8A2J7nvyT8g17YzbSfOviEWrghazKZbHbig@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/.