0229106afa
40af10b57 changed things so we make use of a generation memory context for storing tuples to be sorted by tuplesort.c. That change does not play nicely with the changes made in 9f03ca915 (back in 2014). That commit changed things so that index_form_tuple() is called while switched into the tuplestore's tuplecontext. In order to fetch the tuple from the index, index_form_tuple() must do various memory allocations which are unrelated to the storage of the final returned tuple. Although all of these allocations are pfree'd, the fact that we now use a generation context means that the memory for these pfree'd allocations won't be used again by any other allocation due to generation.c's lack of freelists. This could result in sorts used for building indexes exceeding maintenance_work_mem by a very large amount. Here we fix it so we no longer allocate anything apart from the tuple itself into the generation context by adding a new version of index_form_tuple named index_form_tuple_context, which can be called to specify the MemoryContext to allocate the tuple into. Discussion: https://postgr.es/m/CAApHDvrHQkiFRHiGiAS-LMOvJN-eK-s762=tVzBz8ZqUea-a_A@mail.gmail.com Backpatch-through: 15, where 40af10b57 was added.
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/.