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GIN index scans were not taking any descent CPU-based cost into account. That made them look cheaper than other types of indexes when they shouldn't be. We use the same heuristic as for btree indexes, but multiply it by the number of searched entries. Additionally, the CPU cost for the tree was based largely on a genericcostestimate. For a GIN index, we should not charge index quals per tuple, but per entry. On top of this, charge cpu_index_tuple_cost per actual tuple. This should fix the cases where a GIN index is preferred over a btree and the ones where a memoize node is not added on top of the GIN index scan because it seemed too cheap. We don't packpatch this to evade unexpected plan changes in stable versions. Discussion: https://postgr.es/m/CABs3KGQnOkyQ42-zKQqiE7M0Ks9oWDSee%3D%2BJx3-TGq%3D68xqWYw%40mail.gmail.com Discussion: https://postgr.es/m/3188617.44csPzL39Z%40aivenronan Author: Ronan Dunklau Reported-By: Hung Nguyen Reviewed-by: Tom Lane, Alexander Korotkov
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/.