8000 Sync back-branch copies of the timezone code with IANA release tzcode… · linearregression/postgres@5db14fa · GitHub
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Sync back-branch copies of the timezone code with IANA release tzcode2016c.
Back-patch commit 1c1a7cb, along with subsequent portability fixes, into all active branches. Also, back-patch commits 6960277 and 5968570 (addition of zic -P option) into 9.1 and 9.2, just to reduce differences between the branches. src/timezone/ is now largely identical in all active branches, except that in 9.1, pgtz.c retains the initial-timezone-selection code that was moved over to initdb in 9.2. Ordinarily we wouldn't risk this much code churn in back branches, but it seems necessary in this case, because among the changes are two feature additions in the "zic" zone data file compiler (a larger limit on the number of allowed DST transitions, and addition of a "%z" escape in zone abbreviations). IANA have not yet started to use those features in their tzdata files, but presumably they will before too long. If we don't update then we'll be unable to adopt new timezone data. Also, installations built with --with-system-tzdata (which includes most distro-supplied builds, I believe) might fail even if we don't update our copies of the data files. There are assorted bug fixes too, mostly affecting obscure timezones or post-2037 dates. Discussion: <13601.1468868947@sss.pgh.pa.us>
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‎src/timezone/.gitignore

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/zic
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/abbrevs.txt

‎src/timezone/Makefile

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OBJS= localtime.o strftime.o pgtz.o
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# files needed to build zic utility program
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ZICOBJS= zic.o ialloc.o scheck.o localtime.o
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ZICOBJS= zic.o
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# timezone data files
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TZDATA = africa antarctica asia australasia europe northamerica southamerica \
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# We could do this test in the action section:
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# $(if $(ZIC),$(ZIC),./zic)
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# but gmake versions <= 3.78.1 or perhaps later have a bug
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# that causes a segfault; gmake 3.81 or later fixes this.
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# but GNU make versions <= 3.78.1 or perhaps later have a bug
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# that causes a segfault; GNU make 3.81 or later fixes this.
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ifeq (,$(ZIC))
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ZIC= ./zic
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endif
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endif
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$(MAKE) -C tznames $@
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abbrevs.txt: zic $(TZDATAFILES)
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mkdir junkdir
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$(ZIC) -P -d junkdir -p '$(POSIXRULES)' $(TZDATAFILES) | LANG=C sort | uniq >abbrevs.txt
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rm -rf junkdir
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installdirs:
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$(MKDIR_P) '$(DESTDIR)$(datadir)'
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$(MAKE) -C tznames $@
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clean distclean maintainer-clean:
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rm -f zic$(X) $(ZICOBJS)
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rm -f zic$(X) $(ZICOBJS) abbrevs.txt

‎src/timezone/README

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src/timezone/README
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Timezone
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========
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This is a PostgreSQL adapted version of the IANA timezone library from
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This is a PostgreSQL adapted version of the timezone library from
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http://www.iana.org/time-zones
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http://www.iana.org/time-zones
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The source code can be found at:
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The latest versions of both the tzdata and tzcode tarballs are normally
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available right from that page. Historical versions can be found
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elsewhere on the site.
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ftp://ftp.iana.org/tz/releases/tzcode*.tar.gz
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The code is currently synced with release 2010c. There are many cosmetic
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(and not so cosmetic) differences from the original tzcode library, but
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diffs in the upstream version should usually be propagated to our version.
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Since time zone rules change frequently in some parts of the world,
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we should endeavor to update the data files before each PostgreSQL
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release. The code need not be updated as often, but we must track
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changes that might affect interpretation of the data files.
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The data files under data/ are an exact copy of the latest data set from:
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ftp://ftp.iana.org/tz/releases/tzdata*.tar.gz
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Time Zone data
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==============
2019

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Since time zone rules change frequently in some parts of the world,
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we should endeavor to update the data files before each PostgreSQL
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release.
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The data files under data/ are an exact copy of the latest tzdata set,
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except that we omit some files that are not of interest for our purposes.
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At each update, we should check if time zone offsets have changed.
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Just search for the current or previous year and see what has changed.
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Sometimes a country changes its time zone offsets, for example Georgia
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in 2004. Just grepping in the zic database files for 2004 is enough to
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spot such a change. Then the files under tznames/ should be updated.
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While the files under data/ can just be duplicated when updating, manual
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effort is needed to update the time zone abbreviation lists under tznames/.
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These need to be changed whenever new abbreviations are invented or the
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UTC offset associated with an existing abbreviation changes. To detect
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if this has happened, after installing new files under data/ do
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make abbrevs.txt
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which will produce a file showing all abbreviations that are in current
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use according to the data/ files. Compare this to known_abbrevs.txt,
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which is the list that existed last time the tznames/ files were updated.
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Update tznames/ as seems appropriate, then replace known_abbrevs.txt
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in the same commit. Usually, if a known abbreviation has changed meaning,
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the appropriate fix is to make it refer to a long-form zone name instead
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of a fixed GMT offset.
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When there has been a new release of Windows (probably including Service
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Packs), the list of matching timezones need to be updated. Run the
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script in src/tools/win32tzlist.pl on a Windows machine running this new
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release and apply any new timezones that it detects. Never remove any
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mappings in case they are removed in Windows, since we still need to
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match properly on the old version.
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Time Zone code
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==============
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The code in this directory is currently synced with tzcode release 2016c.
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There are many cosmetic (and not so cosmetic) differences from the
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original tzcode library, but diffs in the upstream version should usually
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be propagated to our version. Here are some notes about that.
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For the most part we want to use the upstream code as-is, but there are
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several considerations preventing an exact match:
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* For readability/maintainability we reformat the code to match our own
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conventions; this includes pgindent'ing it and getting rid of upstream's
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overuse of "register" declarations. (It used to include conversion of
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old-style function declarations to C89 style, but thank goodness they
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fixed that.)
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* We need the code to follow Postgres' portability conventions; this
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includes relying on configure's results rather than hand-hacked #defines,
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and not relying on <stdint.h> features that may not exist on old systems.
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(In particular this means using Postgres' definitions of the int32 and
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int64 typedefs, not int_fast32_t/int_fast64_t.)
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* Since Postgres is typically built on a system that has its own copy
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of the <time.h> functions, we must avoid conflicting with those. This
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mandates renaming typedef time_t to pg_time_t, and similarly for most
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other exposed names.
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* We have exposed the tzload() and tzparse() internal functions, and
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slightly modified the API of the former, in part because it now relies
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on our own pg_open_tzfile() rather than opening files for itself.
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* There's a fair amount of code we don't need and have removed,
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including all the nonstandard optional APIs. We have also added
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a few functions of our own at the bottom of localtime.c.
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* In zic.c, we have added support for a -P (print_abbrevs) switch, which
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is used to create the "abbrevs.txt" summary of currently-in-use zone
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abbreviations that was described above.
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The most convenient way to compare a new tzcode release to our code is
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to first run the tzcode source files through a sed filter like this:
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sed -r \
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-e 's/^([ \t]*)\*\*([ \t])/\1 *\2/' \
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-e 's/^([ \t]*)\*\*$/\1 */' \
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-e 's|^\*/| */|' \
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-e 's/\bregister[ \t]//g' \
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-e 's/int_fast32_t/int32/g' \
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-e 's/int_fast64_t/int64/g' \
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-e 's/struct[ \t]+tm\b/struct pg_tm/g' \
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-e 's/\btime_t\b/pg_time_t/g' \
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and then run them through pgindent. (The first three sed patterns deal
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with conversion of their block comment style to something pgindent
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won't make a hash of; the remainder address other points noted above.)
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After that, the files can be diff'd directly against our corresponding
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files.

‎src/timezone/ialloc.c

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