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A manifest is a JSON document which includes (1) the file name, size, last modification time, and an optional checksum for each file backed up, (2) timelines and LSNs for whatever WAL will need to be replayed to make the backup consistent, and (3) a checksum for the manifest itself. By default, we use CRC-32C when checksumming data files, because we are trying to detect corruption and user error, not foil an adversary. However, pg_basebackup and the server-side BASE_BACKUP command now have options to select a different algorithm, so users wanting a cryptographic hash function can select SHA-224, SHA-256, SHA-384, or SHA-512. Users not wanting file checksums at all can disable them, or disable generating of the backup manifest altogether. Using a cryptographic hash function in place of CRC-32C consumes significantly more CPU cycles, which may slow down backups in some cases. A new tool called pg_validatebackup can validate a backup against the manifest. If no checksums are present, it can still check that the right files exist and that they have the expected sizes. If checksums are present, it can also verify that each file has the expected checksum. Additionally, it calls pg_waldump to verify that the expected WAL files are present and parseable. Only plain format backups can be validated directly, but tar format backups can be validated after extracting them. Robert Haas, with help, ideas, review, and testing from David Steele, Stephen Frost, Andrew Dunstan, Rushabh Lathia, Suraj Kharage, Tushar Ahuja, Rajkumar Raghuwanshi, Mark Dilger, Davinder Singh, Jeevan Chalke, Amit Kapila, Andres Freund, and Noah Misch. Discussion: http://postgr.es/m/CA+TgmoZV8dw1H2bzZ9xkKwdrk8+XYa+DC9H=F7heO2zna5T6qg@mail.gmail.com |
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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/.