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pg_dump produces custom-format archive files that lack data offsets when it is unable to seek its output. Up to now that's been a hazard for pg_restore. But if pg_restore is able to seek in the archive file, there is no reason to throw up our hands when asked to restore data blocks out of order. Instead, whenever we are searching for a data block, record the locations of the blocks we passed over (that is, fill in the missing data-offset fields in our in-memory copy of the TOC data). Then, when we hit a case that requires going backwards, we can just seek back. Also track the furthest point that we've searched to, and seek back to there when beginning a search for a new data block. This avoids possible O(N^2) time consumption, by ensuring that each data block is examined at most twice. (On Unix systems, that's at most twice per parallel-restore job; but since Windows uses threads here, the threads can share block location knowledge, reducing the amount of duplicated work.) We can also improve the code a bit by using fseeko() to skip over data blocks during the search. This is all of some use even in simple restores, but it's really significant for parallel pg_restore. In that case, we require seekability of the input already, and we will very probably need to do out-of-order restores. Back-patch to v12, as this fixes a regression introduced by commit 548e50976. Before that, parallel restore avoided requesting out-of-order restores, so it would work on a data-offset-less archive. Now it will again. Ideally this patch would include some test coverage, but there are other open bugs that need to be fixed before we can extend our coverage of parallel restore very much. Plan to revisit that later. David Gilman and Tom Lane; reviewed by Justin Pryzby Discussion: https://postgr.es/m/CALBH9DDuJ+scZc4MEvw5uO-=vRyR2=QF9+Yh=3hPEnKHWfS81A@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. 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/.