c8b2499111
The previous coding first generated a uniform random value between 0.0 and 1.0, then converted that to an integer between 1 and 10000, and divided that again by 10000. Those conversions are unnecessary; we can use the double value that pg_erand48() returns directly. While we're at it, put the logic into a helper function, getPoissonRand(). The largest delay generated by the old coding was about 9.2 times the average, because of the way the uniformly distributed value used for the calculation was truncated to 1/10000 granularity. The new coding doesn't have such clamping. With my laptop's DBL_MIN value, the maximum delay with the new coding is about 700x the average. That seems acceptable - any reasonable pgbench session should last long enough to average that out. Backpatch to 9.4.
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/.