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When building append paths, we've been looking only at startup and total costs for the paths. When building fractional paths that may eliminate the cheapest one, because it may be dominated by two separate paths (one for startup, one for total cost). This extends generate_orderedappend_paths() to also consider which paths have lowest fractional cost. Currently we only consider paths matching pathkeys - in the future this may be improved by also considering paths that are only partially sorted, with an incremental sort on top. Original report of an issue by Arne Roland, patch by me (based on a suggestion by Tom Lane). Reviewed-by: Arne Roland, Zhihong Yu Discussion: https://postgr.es/m/e8f9ec90-546d-e948-acce-0525f3e92773%40enterprisedb.com Discussion: https://postgr.es/m/1581042da8044e71ada2d6e3a51bf7bb%40index.de
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/.