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We sometimes insert a ProjectionPath into a plan tree when projection is not strictly required. The existing code already arranges to avoid emitting a Result node when the ProjectionPath's subpath can perform the projection itself, but previously it didn't consider the possibility that the parent node might not actually require the projection to be performed at all. Skipping projection when it's not required can not only avoid Result nodes that aren't needed, but also avoid losing the "physical tlist" optimization unneccessarily. Patch by me, reviewed by Amit Kapila. Discussion: http://postgr.es/m/CA+TgmoakT5gmahbPWGqrR2nAdFOMAOnOXYoWHRdVfGWs34t6_A@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. PostgreSQL has many language interfaces, many of which are listed here: https://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. 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 https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.