e4326fbc60
Previously, the code charged disable_cost for CurrentOfExpr, and then subtracted disable_cost from the cost of a TID path that used CurrentOfExpr as the TID qual, effectively disabling all paths except that one. Now, we instead suppress generation of the disabled paths entirely, and generate only the one that the executor will actually understand. With this approach, we do not need to rely on disable_cost being large enough to prevent the wrong path from being chosen, and we save some CPU cycle by avoiding generating paths that we can't actually use. In my opinion, the code is also easier to understand like this. Patch by me. Review by Heikki Linnakangas. Discussion: http://postgr.es/m/591b3596-2ea0-4b8e-99c6-fad0ef2801f5@iki.fi
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/.