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"Blind writes" are a mechanism to push buffers down to disk when evicting them; since they may belong to different databases than the one a backend is connected to, the backend does not necessarily have a relation to link them to, and thus no way to blow them away. We were keeping those files open indefinitely, which would cause a problem if the underlying table was deleted, because the operating system would not be able to reclaim the disk space used by those files. To fix, have bufmgr mark such files as transient to smgr; the lower layer is allowed to close the file descriptor when the current transaction ends. We must be careful to have any other access of the file to remove the transient markings, to prevent unnecessary expensive system calls when evicting buffers belonging to our own database (which files we're likely to require again soon.) |
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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/.