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Since hash indexes typically have very few overflow pages, adding a new splitpoint essentially doubles the on-disk size of the index, which can lead to large and abrupt increases in disk usage (and perhaps long delays on occasion). To mitigate this problem to some degree, divide larger splitpoints into four equal phases. This means that, for example, instead of growing from 4GB to 8GB all at once, a hash index will now grow from 4GB to 5GB to 6GB to 7GB to 8GB, which is perhaps still not as smooth as we'd like but certainly an improvement. This changes the on-disk format of the metapage, so bump HASH_VERSION from 2 to 3. This will force a REINDEX of all existing hash indexes, but that's probably a good idea anyway. First, hash indexes from pre-10 versions of PostgreSQL could easily be corrupted, and we don't want to confuse corruption carried over from an older release with any corruption caused despite the new write-ahead logging in v10. Second, it will let us remove some backward-compatibility code added by commit 293e24e507838733aba4748b514536af2d39d7f2. Mithun Cy, reviewed by Amit Kapila, Jesper Pedersen and me. Regression test outputs updated by me. Discussion: http://postgr.es/m/CAD__OuhG6F1gQLCgMQNnMNgoCvOLQZz9zKYJQNYvYmmJoM42gA@mail.gmail.com Discussion: http://postgr.es/m/CA+TgmoYty0jCf-pa+m+vYUJ716+AxM7nv_syvyanyf5O-L_i2A@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: http://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 http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.