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WindowFuncs such as row_number() don't care if it's called with ROWS UNBOUNDED PRECEDING AND CURRENT ROW or with RANGE UNBOUNDED PRECEDING AND CURRENT ROW. The latter is less efficient as the RANGE option requires that the executor check for peer rows, so using the ROW option instead would cause less overhead. Because RANGE is part of the default frame options for WindowClauses, it means WindowAgg is, by default, working much harder than it needs to for window functions where the ROWS / RANGE option has no effect on the window function's result. On a test query from the discussion thread, a performance improvement of 344% was seen by using ROWS instead of RANGE. Here we add a new support function node type to allow support functions to be called for window functions so that the most optimal version of the frame options can be set. The planner has been adjusted so that the frame options are changed only if all window functions sharing the same window clause agree on what the optimized frame options are. Here we give the ability for row_number(), rank(), dense_rank(), percent_rank(), cume_dist() and ntile() to alter their WindowClause's frameOptions. Reviewed-by: Vik Fearing, Erwin Brandstetter, Zhihong Yu Discussion: https://postgr.es/m/CAGHENJ7LBBszxS+SkWWFVnBmOT2oVsBhDMB1DFrgerCeYa_DyA@mail.gmail.com Discussion: https://postgr.es/m/CAApHDvohAKEtTXxq7Pc-ic2dKT8oZfbRKeEJP64M0B6+S88z+A@mail.gmail.com |
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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: 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/.