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PostgreSQL was calling GetSystemTime followed by SystemTimeToFileTime in the win32 port gettimeofday function. This is not necessary and limits the reported precision to the 1ms granularity that the SYSTEMTIME struct can represent. By using GetSystemTimeAsFileTime we avoid unnecessary conversions and capture timestamps at 100ns granularity, which is then rounded to 1µs granularity for storage in a PostgreSQL timestamp. On most Windows systems this change will actually have no significant effect on timestamp resolution as the system timer tick is typically between 1ms and 15ms depending on what timer resolution currently running applications have requested. You can check this with clockres.exe from sysinternals. Despite the platform limiation this change still permits capture of finer timestamps where the system is capable of producing them and it gets rid of an unnecessary syscall. The higher resolution GetSystemTimePreciseAsFileTime call available on Windows 8 and Windows Server 2012 has the same interface as GetSystemTimeAsFileTime, so switching to GetSystemTimeAsFileTime makes it easier to use the Precise variant later. Craig Ringer, reviewed by David Rowley
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/.