c0962a113d
This commit implements the automatic conversion of 'x IN (VALUES ...)' into ScalarArrayOpExpr. That simplifies the query tree, eliminating the appearance of an unnecessary join. Since VALUES describes a relational table, and the value of such a list is a table row, the optimizer will likely face an underestimation problem due to the inability to estimate cardinality through MCV statistics. The cardinality evaluation mechanism can work with the array inclusion check operation. If the array is small enough (< 100 elements), it will perform a statistical evaluation element by element. We perform the transformation in the convert_ANY_sublink_to_join() if VALUES RTE is proper and the transformation is convertible. The conversion is only possible for operations on scalar values, not rows. Also, we currently support the transformation only when it ends up with a constant array. Otherwise, the evaluation of non-hashed SAOP might be slower than the corresponding Hash Join with VALUES. Discussion: https://postgr.es/m/0184212d-1248-4f1f-a42d-f5cb1c1976d2%40tantorlabs.com Author: Alena Rybakina <a.rybakina@postgrespro.ru> Author: Andrei Lepikhov <lepihov@gmail.com> Reviewed-by: Ivan Kush <ivan.kush@tantorlabs.com> Reviewed-by: Alexander Korotkov <aekorotkov@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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.