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118461114e
match in antijoin mode, we should advance to next outer tuple not next inner. We know we don't want to return this outer tuple, and there is no point in advancing over matching inner tuples now, because we'd just have to do it again if the next outer tuple has the same merge key. This makes a noticeable difference if there are lots of duplicate keys in both inputs. Similarly, after finding a match in semijoin mode, arrange to advance to the next outer tuple after returning the current match; or immediately, if it fails the extra quals. The rationale is the same. (This is a performance bug in existing releases; perhaps worth back-patching? The planner tries to avoid using mergejoin with lots of duplicates, so it may not be a big issue in practice.) Nestloop and hash got this right to start with, but I made some cosmetic adjustments there to make the corresponding bits of logic look more similar. |
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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. PostgreSQL has many language interfaces, many of which are listed here: http://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Changes between all PostgreSQL releases are recorded in the file HISTORY. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.