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We already skip rewriting the table in these cases, but we still force a whole table scan to validate the data. This can be skipped, and thus we can make the whole ALTER TABLE operation just do some catalog touches instead of scanning the table, when these two conditions hold: (a) Old and new pg_constraint.conpfeqop match exactly. This is actually stronger than needed; we could loosen things by way of operator families, but it'd require a lot more effort. (b) The functions, if any, implementing a cast from the foreign type to the primary opcintype are the same. For this purpose, we can consider a binary coercion equivalent to an exact type match. When the opcintype is polymorphic, require that the old and new foreign types match exactly. (Since ri_triggers.c does use the executor, the stronger check for polymorphic types is no mere future-proofing. However, no core type exercises its necessity.) Author: Noah Misch Committer's note: catalog version bumped due to change of the Constraint node. I can't actually find any way to have such a node in a stored rule, but given that we have "out" support for them, better be safe. |
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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: http://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. Changes between all PostgreSQL releases are recorded in the file HISTORY. 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 http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.