b8f1c62807
Add comments explaining when and where it is safe for nbtree to treat row compare keys as if they were simple scalar inequality keys on the row's most significant column. This is particularly important within _bt_advance_array_keys, which deals with required inequality keys in a general and uniform way, without any special handling for row compares. Also spell out the implications of _bt_check_rowcompare's approach of _conditionally_ evaluating lower-order row compare subkeys, particularly when one of its lower-order subkeys might see NULL index tuple values (these may or may not affect whether the qual as a whole is satisfied). The behavior in this area isn't particularly intuitive, so these issues seem worth going into. In passing, add a few more defensive/documenting row comparison related assertions to _bt_first and _bt_check_rowcompare. Follow-up to commitsbd3f59fdandec986020. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Victor Yegorov <vyegorov@gmail.com> Reviewed-By: Chao Li <li.evan.chao@gmail.com> Discussion: https://postgr.es/m/CAH2-Wznwkak_K7pcAdv9uH8ZfNo8QO7+tHXOaCUddMeTfaCCFw@mail.gmail.com 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/.