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When decompressing some input data, the calculation for the initial starting point and the initial size were incorrect, potentially leading to failures when decompressing contents with LZ4. These initialization points are fixed in this commit, bringing the logic closer to what exists for gzip and zstd. The contents of the compressed data is clear (for example backups taken with LZ4 can still be decompressed with a "lz4" command), only the decompression part reading the input data was impacted by this issue. This code path impacts pg_basebackup and pg_verifybackup, which can use the LZ4 decompression routines with an archive streamer, or any tools that try to use the archive streamers in src/fe_utils/. The issue is easier to reproduce with files that have a low-compression rate, like ones filled with random data, for a size of at least 512kB, but this could happen with anything as long as it is stored in a data folder. Some tests are added based on this idea, with a file filled with random bytes grabbed from the backend, written at the root of the data folder. This is proving good enough to reproduce the original problem. Author: Mikhail Gribkov <youzhick@gmail.com> Discussion: https://postgr.es/m/CAMEv5_uQS1Hg6KCaEP2JkrTBbZ-nXQhxomWrhYQvbdzR-zy-wA@mail.gmail.com Backpatch-through: 15
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/.