c902bd57af
We have some limited ability to detect redundant and contradictory conditions involving an nbtree row comparison key following commitsf09816a0andbd3f59fd: we can do so in simple cases involving IS NULL and IS NOT NULL keys on a row compare key's first column. We can likewise determine that a scan's qual is unsatisfiable given a row compare whose first subkey's arg is NULL. Update obsolete comments that claimed that we merely copied row compares into the output key array "without any editorialization". Also update another _bt_preprocess_keys header comment paragraph: add a parenthetical remark that points out that preprocessing will generate a skip array for the preceding example qual. That will ultimate lead to preprocessing marking the example's lower-order y key required -- which is exactly what the example supposes cannot happen. Keep the original comment, though, since it accurately describes the mechanical rules that determine which keys get marked required in the absence of skip arrays (which can occasionally still matter). This fixes an oversight in commit92fe23d9, which added the nbtree skip scan optimization. Author: Peter Geoghegan <pg@bowt.ie> Backpatch-through: 18
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/.