c8d2f68cc8
Currently, the function expr_is_nonnullable() checks only Const and
Var expressions to determine if an expression is non-nullable. This
patch extends the detection logic to handle more expression types.
This can enable several downstream optimizations, such as reducing
NullTest quals to constant truth values (e.g., "COALESCE(var, 1) IS
NULL" becomes FALSE) and converting "COUNT(expr)" to the more
efficient "COUNT(*)" when the expression is proven non-nullable.
This breaks a test case in test_predtest.sql, since we now simplify
"ARRAY[] IS NULL" to constant FALSE, preventing it from weakly
refuting a strict ScalarArrayOpExpr ("x = any(ARRAY[])"). To ensure
the refutation logic is still exercised as intended, wrap the array
argument in opaque_array().
Author: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Tender Wang <tndrwang@gmail.com>
Reviewed-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Matheus Alcantara <matheusssilv97@gmail.com>
Discussion: https://postgr.es/m/CAMbWs49UhPBjm+NRpxerjaeuFKyUZJ_AjM3NBcSYK2JgZ6VTEQ@mail.gmail.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.
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/.