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e94568ecc1
Don't pre-read tuples into SortTuple slots during merge. Instead, use the memory for larger read buffers in logtape.c. We're doing the same number of READTUP() calls either way, but managing the pre-read SortTuple slots is much more complicated. Also, the on-tape representation is more compact than SortTuples, so we can fit more pre-read tuples into the same amount of memory this way. And we have better cache-locality, when we use just a small number of SortTuple slots. Now that we only hold one tuple from each tape in the SortTuple slots, we can greatly simplify the "batch memory" management. We now maintain a small set of fixed-sized slots, to hold the tuples, and fall back to palloc() for larger tuples. We use this method during all merge phases, not just the final merge, and also when randomAccess is requested, and also in the TSS_SORTEDONTAPE case. In other words, it's used whenever we do an external sort. Reviewed by Peter Geoghegan and Claudio Freire. Discussion: <CAM3SWZTpaORV=yQGVCG8Q4axcZ3MvF-05xe39ZvORdU9JcD6hQ@mail.gmail.com> |
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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/.