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Make pg_interpret_timezone_abbrev() check sp->defaulttype too.

This omission caused it to not recognize the furthest-back zoneabbreviation when working with timezone data compiled with relativelyrecent zic (2018f or newer). Older versions of zic produced a dummyDST transition at the Big Bang, so that the oldest abbreviation couldalways be found in the sp->types[] array; but newer versions don't dothat, so that we must examine defaulttype as well as the types[] arrayto be sure of seeing all the abbreviations.While this has been broken for six or so years, we'd managed notto notice for two reasons: (1) many platforms are still usingancient zic for compatibility reasons, so that the issue did notmanifest in builds using --with-system-tzdata; (2) the oldestzone abbreviation is almost always "LMT", which we weren'tsupporting anyway (but an upcoming patch will accept that).While at it, update pg_next_dst_boundary() to use sp->defaulttypeas the time type for non-DST zones and times before the oldestDST transition. The existing code there predates upstream'sinvention of the sp->defaulttype field, and its heuristic forfinding the oldest time type has now been subsumed into thecode that sets sp->defaulttype.Possibly this should be back-patched, but I'm not currently awareof any visible consequences of this bug in released branches.Per report from Aleksander Alekseev and additional investigation.Discussion:https://postgr.es/m/CAJ7c6TOATjJqvhnYsui0=CO5XFMF4dvTGH+skzB--jNhqSQu5g@mail.gmail.com

1 parent901bd4a commitbc10219Copy full SHA for bc10219

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src/timezone
- localtime.c

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`‎src/timezone/localtime.c`

Lines changed: 20 additions & 20 deletions

Original file line number	Diff line number	Diff line change
`@@ -1624,15 +1624,8 @@ pg_next_dst_boundary(const pg_time_t *timep,`
`1624`	`1624`	`sp=&tz->state;`
`1625`	`1625`	`if (sp->timecnt==0)`
`1626`	`1626`	`{`
`1627`		`-/* non-DST zone, use lowest-numbered standard type */`
`1628`		`-i=0;`
`1629`		`-while (sp->ttis[i].tt_isdst)`
`1630`		`-if (++i >=sp->typecnt)`
`1631`		`-{`
`1632`		`-i=0;`
`1633`		`-break;`
`1634`		`-}`
`1635`		`-ttisp=&sp->ttis[i];`
	`1627`	`+/* non-DST zone, use the defaulttype */`
	`1628`	`+ttisp=&sp->ttis[sp->defaulttype];`
`1636`	`1629`	`*before_gmtoff=ttisp->tt_utoff;`
`1637`	`1630`	`*before_isdst=ttisp->tt_isdst;`
`1638`	`1631`	`return0;`
`@@ -1692,15 +1685,8 @@ pg_next_dst_boundary(const pg_time_t *timep,`
`1692`	`1685`	`}`
`1693`	`1686`	`if (t<sp->ats[0])`
`1694`	`1687`	`{`
`1695`		`-/* For "before", use lowest-numbered standard type */`
`1696`		`-i=0;`
`1697`		`-while (sp->ttis[i].tt_isdst)`
`1698`		`-if (++i >=sp->typecnt)`
`1699`		`-{`
`1700`		`-i=0;`
`1701`		`-break;`
`1702`		`-}`
`1703`		`-ttisp=&sp->ttis[i];`
	`1688`	`+/* For "before", use the defaulttype */`
	`1689`	`+ttisp=&sp->ttis[sp->defaulttype];`
`1704`	`1690`	`*before_gmtoff=ttisp->tt_utoff;`
`1705`	`1691`	`*before_isdst=ttisp->tt_isdst;`
`1706`	`1692`	`*boundary=sp->ats[0];`
`@@ -1793,7 +1779,9 @@ pg_interpret_timezone_abbrev(const char *abbrev,`
`1793`	`1779`	`* abbreviation should get us what we want, since extrapolation would just`
`1794`	`1780`	`* be repeating the newest or oldest meanings.`
`1795`	`1781`	`*`
`1796`		`- * Use binary search to locate the first transition > cutoff time.`
	`1782`	`+ * Use binary search to locate the first transition > cutoff time. (Note`
	`1783`	`+ * that sp->timecnt could be zero, in which case this loop does nothing`
	`1784`	`+ * and only the defaulttype entry will be checked.)`
`1797`	`1785`	`*/`
`1798`	`1786`	`{`
`1799`	`1787`	`intlo=0;`
`@@ -1827,7 +1815,19 @@ pg_interpret_timezone_abbrev(const char *abbrev,`
`1827`	`1815`	`}`
`1828`	`1816`
`1829`	`1817`	`/*`
`1830`		`- * Not there, so scan forwards to find the first one after.`
	`1818`	`+ * Not found yet; check the defaulttype, which is notionally the era`
	`1819`	`+ * before any of the entries in sp->types[].`
	`1820`	`+ */`
	`1821`	`+ttisp=&sp->ttis[sp->defaulttype];`
	`1822`	`+if (ttisp->tt_desigidx==abbrind)`
	`1823`	`+{`
	`1824`	`+*gmtoff=ttisp->tt_utoff;`
	`1825`	`+*isdst=ttisp->tt_isdst;`
	`1826`	`+return true;`
	`1827`	`+}`
	`1828`	`+`
	`1829`	`+/*`
	`1830`	`+ * Not there, so scan forwards to find the first one after the cutoff.`
`1831`	`1831`	`*/`
`1832`	`1832`	`for (i=cutoff;i<sp->timecnt;i++)`
`1833`	`1833`	`{`

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`‎src/timezone/localtime.c`

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