cf2acaf4dc
Streamline handling of the various strategies that we have to avoid a page split in nbtinsert.c. When it looks like a leaf page is about to overflow, we now perform deleting LP_DEAD items and deduplication in one central place. This greatly simplifies _bt_findinsertloc(). This has an independently useful consequence: nbtree no longer relies on the BTP_HAS_GARBAGE page level flag/hint for anything important. We still set and unset the flag in the same way as before, but it's no longer treated as a gating condition when considering if we should check for already-set LP_DEAD bits. This happens at the point where the page looks like it might have to be split anyway, so simply checking the LP_DEAD bits in passing is practically free. This avoids missing LP_DEAD bits just because the page-level hint is unset, which is probably reasonably common (e.g. it happens when VACUUM unsets the page-level flag without actually removing index tuples whose LP_DEAD-bit was set recently, after the VACUUM operation began but before it reached the leaf page in question). Note that this isn't a big behavioral change compared to PostgreSQL 13. We were already checking for set LP_DEAD bits regardless of whether the BTP_HAS_GARBAGE page level flag was set before we considered doing a deduplication pass. This commit only goes slightly further by doing the same check for all indexes, even indexes where deduplication won't be performed. We don't completely remove the BTP_HAS_GARBAGE flag. We still rely on it as a gating condition with pg_upgrade'd indexes from before B-tree version 4/PostgreSQL 12. That makes sense because we sometimes have to make a choice among pages full of duplicates when inserting a tuple with pre version 4 indexes. It probably still pays to avoid accessing the line pointer array of a page there, since it won't yet be clear whether we'll insert on to the page in question at all, let alone split it as a result. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Victor Yegorov <vyegorov@gmail.com> Discussion: https://postgr.es/m/CAH2-Wz%3DYpc1PDdk8OVJDChGJBjT06%3DA0Mbv9HyTLCsOknGcUFg%40mail.gmail.com |
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README
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/.