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Commit 36a35c55 changed the divisor from 3 to 6, for no apparent reason. Reducing GinMaxItemSize like that created a dump/reload hazard: loading a 9.3 database to 9.4 might fail with "index row size XXX exceeds maximum 1352 for index ..." error. Revert the change. While we're at it, make the calculation slightly more accurate. It used to divide the available space on page by three, then subtract sizeof(ItemIdData), and finally round down. That's not totally accurate; the item pointers for the three items are packed tight right after the page header, but there is alignment padding after the item pointers. Change the calculation to reflect that, like BTMaxItemSize does. I tested this with different block sizes on systems with 4- and 8-byte alignment, and the value after the final MAXALIGN_DOWN was the same with both methods on all configurations. So this does not make any difference currently, but let's be tidy. Also add a comment explaining what the macro does. This fixes bug #12292 reported by Robert Thaler. Backpatch to 9.4, where the bug was introduced.
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/.