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This allows simplification of the plan tree in some common usage patterns: we can get rid of a join to the function RTE. In principle we could pull up any immutable expression, but restricting it to Consts avoids the risk that multiple evaluations of the expression might cost more than we can save. (Possibly this could be improved in future --- but we've more or less promised people that putting a function in FROM guarantees single evaluation, so we'd have to tread carefully.) To do this, we need to rearrange when eval_const_expressions() happens for expressions in function RTEs. I moved it to inline_set_returning_functions(), which already has to iterate over every function RTE, and in consequence renamed that function to preprocess_function_rtes(). A useful consequence is that inline_set_returning_function() no longer has to do this for itself, simplifying that code. In passing, break out pull_up_simple_subquery's code that knows where everything that needs pullup_replace_vars() processing is, so that the new pull_up_constant_function() routine can share it. We'd gotten away with one-and-a-half copies of that code so far, since pull_up_simple_values() could assume that a lot of cases didn't apply to it --- but I don't think pull_up_constant_function() can make any simplifying assumptions. Might as well make pull_up_simple_values() use it too. (Possibly this refactoring should go further: maybe we could share some of the code to fill in the pullup_replace_vars_context struct? For now, I left it that the callers fill that completely.) Note: the one existing test case that this patch changes has to be changed because inlining its function RTEs would destroy the point of the test, namely to check join order. Alexander Kuzmenkov and Aleksandr Parfenov, reviewed by Antonin Houska and Anastasia Lubennikova, and whacked around some more by me Discussion: https://postgr.es/m/402356c32eeb93d4fed01f66d6c7fe2d@postgrespro.ru |
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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. 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/.