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This is similar to pg_upgrade's --link option, except that here we won't typically be able to use it for every input file: sometimes we will need to reconstruct a complete backup from blocks stored in different files. However, when a whole file does need to be copied, we can use an optimized copying strategy: see the existing --clone and --copy-file-range options and the code to use CopyFile() on Windows. This commit adds a new strategy: add a hard link to an existing file. Making a hard link doesn't actually copy anything, but it makes sense for the code to treat it as doing so. This is useful when the input directories are merely staging directories that will be removed once the restore is complete. In such cases, there is no need to actually copy the data, and making a bunch of new hard links can be very quick. However, it would be quite dangerous to use it if the input directories might later be reused for any other purpose, since starting postgres on the output directory would destructively modify the input directories. For that reason, using this new option causes pg_combinebackup to emit a warning about the danger involved. Author: Israel Barth Rubio <barthisrael@gmail.com> Co-authored-by: Robert Haas <robertmhaas@gmail.com> (cosmetic changes) Reviewed-by: Vignesh C <vignesh21@gmail.com> Discussion: http://postgr.es/m/CA+TgmoaEFsYHsMefNaNkU=2SnMRufKE3eVJxvAaX=OWgcnPmPg@mail.gmail.com
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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.