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To make this work in the base case, pg_database now has a nailed-in-cache relation descriptor that is initialized using hardwired knowledge in relcache.c. This means pg_database is added to the set of relations that need to have a Schema_pg_xxx macro maintained in pg_attribute.h. When this path is taken, we'll have to do a seqscan of pg_database to find the row we need. In the normal case, we are able to do an indexscan to find the database's row by name. This is made possible by storing a global relcache init file that describes only the shared catalogs and their indexes (and therefore is usable by all backends in any database). A new backend loads this cache file, finds its database OID after an indexscan on pg_database, and then loads the local relcache init file for that database. This change should effectively eliminate number of databases as a factor in backend startup time, even with large numbers of databases. However, the real reason for doing it is as a first step towards getting rid of the flat files altogether. There are still several other sub-projects to be tackled before that can happen.
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/.