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With hundreds of thousands of TOC entries, the repeated searches in reduce_dependencies() become the dominant cost. Get rid of that searching by constructing reverse-dependency lists, which we can do in O(N) time during the fix_dependencies() preprocessing. I chose to store the reverse dependencies as DumpId arrays for consistency with the forward-dependency representation, and keep the previously-transient tocsByDumpId[] array around to locate actual TOC entry structs quickly from dump IDs. While this fixes the slow case reported by Vlad Arkhipov, there is still a potential for O(N^2) behavior with sufficiently many tables: fix_dependencies itself, as well as mark_create_done and inhibit_data_for_failed_table, are doing repeated searches to deal with table-to-table-data dependencies. Possibly this work could be extended to deal with that, although the latter two functions are also used in non-parallel restore where we currently don't run fix_dependencies. Another TODO is that we fail to parallelize restore of multiple blobs at all. This appears to require changes in the archive format to fix. Back-patch to 9.0 where the problem was reported. 8.4 has potential issues as well; but since it doesn't create a separate TOC entry for each blob, it's at much less risk of having enough TOC entries to cause real problems. |
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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/.