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~> (cube, int) operator was especially designed for knn-gist search. However, it appears that knn-gist search can't work correctly with current behavior of this operator when dataset contains cubes of variable dimensionality. In this case, the same value of second operator argument can point to different dimension depending on dimensionality of particular cube. Such behavior is incompatible with gist indexing of cubes, and knn-gist doesn't work correctly for it. This patch changes behavior of ~> (cube, int) operator by introducing dimension numbering where value of second argument unambiguously identifies number of dimension. With new behavior, this operator can be correctly supported by knn-gist. Relevant changes to cube operator class are also included. Backpatch to v9.6 where operator was introduced. Since behavior of ~> (cube, int) operator is changed, depending entities must be refreshed after upgrade. Such as, expression indexes using this operator must be reindexed, materialized views must be rebuilt, stored procedures and client code must be revised to correctly use new behavior. That should be mentioned in release notes. Noticed by: Tomas Vondra Author: Alexander Korotkov Reviewed by: Tomas Vondra, Andrey Borodin Discussion: https://www.postgresql.org/message-id/flat/a9657f6a-b497-36ff-e56-482a2c7e3292@2ndquadrant.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/.