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This avoids unnecessarily creating a RelOptInfo for which we have no actual need. This idea is from Ashutosh Bapat, who wrote a very different patch to accomplish a similar goal. It will be more important if and when we get partition-wise aggregate, since then there could be many partially grouped relations all of which could potentially be unnecessary. In passing, this sets the grouping relation's reltarget, which wasn't done previously but makes things simpler for this refactoring. Along the way, adjust things so that add_paths_to_partial_grouping_rel, now renamed create_partial_grouping_paths, does not perform the Gather or Gather Merge steps to generate non-partial paths from partial paths; have the caller do it instead. This is again for the convenience of partition-wise aggregate, which wants to inject additional partial paths are created and before we decide which ones to Gather/Gather Merge. This might seem like a separate change, but it's actually pretty closely entangled; I couldn't really see much value in separating it and having to change some things twice. Patch by me, reviewed by Ashutosh Bapat. Discussion: http://postgr.es/m/CA+TgmoZ+ZJTVad-=vEq393N99KTooxv9k7M+z73qnTAqkb49BQ@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/.