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Commit 61b313e4 made nbtree consistently pass down a heaprel to low level routines like _bt_getbuf(). Although this was primarily intended as preparation for logical decoding on standbys, it also made it easy to correct an old deficiency in how nbtree VACUUM determines whether or not it's now safe to recycle deleted pages. Pass the heaprel to GlobalVisTestFor() in nbtree routines that deal with recycle safety. nbtree now makes less pessimistic assumptions about recycle safety within non-catalog relations. This enhancement complements the recycling enhancement added by commit 9dd963ae25. nbtree remains just as pessimistic as ever when it comes to recycle safety within indexes on catalog relations. There is no fundamental reason why we need to treat catalog relations differently, though. The behavioral inconsistency is a consequence of the way that nbtree uses nextXID values to implement what Lanin and Shasha call "the drain technique". Note in particular that it has nothing to do with whether or not index tuples might still be required for an older MVCC snapshot. Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com> Discussion: https://postgr.es/m/CAH2-WzkaiDxCje0yPuH=3Uh2p1V_2pFGY==xfbZoZu7Ax_NB8g@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/.