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When the old type is binary coercible to the new type and the using clause does not change the column contents, we can avoid a full table rewrite, though any indexes on the affected columns will still need to be rebuilt. This applies, for example, when changing a varchar column to be of type text. The prior coding assumed that the set of operations that force a rewrite is identical to the set of operations that must be propagated to tables making use of the affected table's rowtype. This is no longer true: even though the tuples in those tables wouldn't need to be modified, the data type change invalidate indexes built using those composite type columns. Indexes on the table we're actually modifying can be invalidated too, of course, but the existing machinery is sufficient to handle that case. Along the way, add some debugging messages that make it possible to understand what operations ALTER TABLE is actually performing in these cases. Noah Misch and Robert Haas
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/.