cc9daa09ee
In sort_inner_and_outer, we create mergejoin join paths by explicitly sorting both relations on each possible ordering of the available mergejoin clauses. However, if there are no available mergejoin clauses, we can skip this process entirely. This patch introduces a check for mergeclause_list at the beginning of sort_inner_and_outer and exits the function if it is found to be empty. This might help skip all the statements that come before the call to select_outer_pathkeys_for_merge, including the build of UniquePaths in the case of JOIN_UNIQUE_OUTER or JOIN_UNIQUE_INNER. I doubt there's any measurable performance improvement, but throughout the run of the regression tests, sort_inner_and_outer is called a total of 44,424 times. Among these calls, there are 11,064 instances where mergeclause_list is found to be empty, which accounts for approximately one-fourth. I think this suggests that implementing this shortcut is worthwhile. Author: Richard Guo Reviewed-by: Ashutosh Bapat Discussion: https://postgr.es/m/CAMbWs48RKiZGFEd5A0JtztRY5ZdvVvNiHh0AKeuoz21F+0dVjQ@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.
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