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Formerly, when using a SQL-spec timezone setting with a fixed GMT offset (called a "brute force" timezone in the code), the session_timezone variable was not updated to match the nominal timezone; rather, all code was expected to ignore session_timezone if HasCTZSet was true. This is of course obviously fragile, though a search of the code finds only timeofday() failing to honor the rule. A bigger problem was that DetermineTimeZoneOffset() supposed that if its pg_tz parameter was pointer-equal to session_timezone, then HasCTZSet should override the parameter. This would cause datetime input containing an explicit zone name to be treated as referencing the brute-force zone instead, if the zone name happened to match the session timezone that had prevailed before installing the brute-force zone setting (as reported in bug #8572). The same malady could affect AT TIME ZONE operators. To fix, set up session_timezone so that it matches the brute-force zone specification, which we can do using the POSIX timezone definition syntax "<abbrev>offset", and get rid of the bogus lookaside check in DetermineTimeZoneOffset(). Aside from fixing the erroneous behavior in datetime parsing and AT TIME ZONE, this will cause the timeofday() function to print its result in the user-requested time zone rather than some previously-set zone. It might also affect results in third-party extensions, if there are any that make use of session_timezone without considering HasCTZSet, but in all cases the new behavior should be saner than before. Back-patch to all supported branches.
src/timezone/README Timezone ======== This is a PostgreSQL adapted version of the timezone library from http://www.iana.org/time-zones The source code can be found at: ftp://ftp.iana.org/tz/releases/tzcode*.tar.gz The code is currently synced with release 2010c. There are many cosmetic (and not so cosmetic) differences from the original tzcode library, but diffs in the upstream version should usually be propagated to our version. The data files under data/ are an exact copy of the latest data set from: ftp://ftp.iana.org/tz/releases/tzdata*.tar.gz Since time zone rules change frequently in some parts of the world, we should endeavor to update the data files before each PostgreSQL release. At each update, we should check if time zone offsets have changed. Just search for the current or previous year and see what has changed. Sometimes a country changes its time zone offsets, for example Georgia in 2004. Just grepping in the zic database files for 2004 is enough to spot such a change. Then the files under tznames/ should be updated. When there has been a new release of Windows (probably including Service Packs), the list of matching timezones need to be updated. Run the script in src/tools/win32tzlist.pl on a Windows machine running this new release and apply any new timezones that it detects. Never remove any mappings in case they are removed in Windows, since we still need to match properly on the old version.