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Formerly various numeric aggregate functions supported parallel aggregation by having each worker convert partial aggregate values to Numeric and use numeric_send() as part of serializing their state. That's problematic, since the range of Numeric is smaller than that of NumericVar, so it's possible for it to overflow (on either side of the decimal point) in cases that would succeed in non-parallel mode. Fix by serializing NumericVars instead, to avoid the overflow risk and ensure that parallel and non-parallel modes work the same. A side benefit is that this improves the efficiency of the serialization/deserialization code, which can make a noticeable difference to performance with large numbers of parallel workers. No back-patch due to risk from changing the binary format of the aggregate serialization states, as well as lack of prior field complaints and low probability of such overflows in practice. Patch by me. Thanks to David Rowley for review and performance testing, and Ranier Vilela for an additional suggestion. Discussion: https://postgr.es/m/CAEZATCUmeFWCrq2dNzZpRj5+6LfN85jYiDoqm+ucSXhb9U2TbA@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: 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/.