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The general usage pattern when we store tuples in tuplesort.c is that we store a series of tuples one by one then either perform a sort or spill them to disk. In the common case, there is no pfreeing of already stored tuples. For the common case since we do not individually pfree tuples, we have very little need for aset.c memory allocation behavior which maintains freelists and always rounds allocation sizes up to the next power of 2 size. Here we conditionally use generation.c contexts for storing tuples in tuplesort.c when the sort will never be bounded. Unfortunately, the memory context to store tuples is already created by the time any calls would be made to tuplesort_set_bound(), so here we add a new sort option that allows callers to specify if they're going to need a bounded sort or not. We'll use a standard aset.c allocator when this sort option is not set. Extension authors must ensure that the TUPLESORT_ALLOWBOUNDED flag is used when calling tuplesort_begin_* for any sorts that make a call to tuplesort_set_bound(). Author: David Rowley Reviewed-by: Andy Fan Discussion: https://postgr.es/m/CAApHDvoH4ASzsAOyHcxkuY01Qf++8JJ0paw+03dk+W25tQEcNQ@mail.gmail.com |
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| README.git | ||
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/.