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Instead of issuing a secondary data-collection query against each table to be dumped, issue just one query, with a WHERE clause restricting it to be applied to only the tables we intend to dump. Likewise for indexes, constraints, and triggers. This greatly reduces the number of queries needed to dump a database containing many tables. It might seem that WHERE clauses listing many target OIDs could be inefficient, but at least on recent server versions this provides a very substantial speedup. (In principle the same thing could be done with other object types such as functions; but that would require significant refactoring of pg_dump, so those will be tackled in a different way in a following patch.) The new WHERE clauses depend on the unnest() function, which is only present in 8.4 and above. We could implement them differently for older servers, but there is an ongoing discussion that will probably result in dropping pg_dump support for servers before 9.2, so that seems like it'd be wasted work. For now, just bump the server version check to require >= 8.4, without stopping to remove any of the code that's thereby rendered dead. We'll mop that situation up soon. Patch by me, based on an idea from Andres Freund. Discussion: https://postgr.es/m/7d7eb6128f40401d81b3b7a898b6b4de@W2012-02.nidsa.loc |
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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/.