Canonicalize ICU locale names to language tags.

Convert to BCP47 language tags before storing in the catalog, except
during binary upgrade or when the locale comes from an existing
collation or template database.

The resulting language tags can vary slightly between ICU
versions. For instance, "@colBackwards=yes" is converted to
"und-u-kb-true" in older versions of ICU, and to the simpler (but
equivalent) "und-u-kb" in newer versions.

The process of canonicalizing to a language tag also understands more
input locale string formats than ucol_open(). For instance,
"fr_CA.UTF-8" is misinterpreted by ucol_open() and the region is
ignored; effectively treating it the same as the locale "fr" and
opening the wrong collator. Canonicalization properly interprets the
language and region, resulting in the language tag "fr-CA", which can
then be understood by ucol_open().

This commit fixes a problem in prior versions due to ucol_open()
misinterpreting locale strings as described above. For instance,
creating an ICU collation with locale "fr_CA.UTF-8" would store that
string directly in the catalog, which would later be passed to (and
misinterpreted by) ucol_open(). After this commit, the locale string
will be canonicalized to language tag "fr-CA" in the catalog, which
will be properly understood by ucol_open(). Because this fix affects
the resulting collator, we cannot change the locale string stored in
the catalog for existing databases or collations; otherwise we'd risk
corrupting indexes. Therefore, only canonicalize locales for
newly-created (not upgraded) collations/databases. For similar
reasons, do not backport.

Discussion: https://postgr.es/m/8c7af6820aed94dc7bc259d2aa7f9663518e6137.camel@j-davis.com
Reviewed-by: Peter Eisentraut

1 files changed, 25 insertions, 21 deletions

diff --git a/src/backend/commands/collationcmds.c b/src/backend/commands/collationcmds.c
index 45de78352c7..c91fe66d9b2 100644
--- a/src/backend/commands/collationcmds.c
+++ b/src/backend/commands/collationcmds.c
@@ -165,6 +165,11 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
 		else
 			colliculocale = NULL;
 
+		/*
+		 * When the ICU locale comes from an existing collation, do not
+		 * canonicalize to a language tag.
+		 */
+
 		datum = SysCacheGetAttr(COLLOID, tp, Anum_pg_collation_collicurules, &isnull);
 		if (!isnull)
 			collicurules = TextDatumGetCString(datum);
@@ -259,6 +264,25 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
 						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
 						 errmsg("parameter \"locale\" must be specified")));
 
+			/*
+			 * During binary upgrade, preserve the locale string. Otherwise,
+			 * canonicalize to a language tag.
+			 */
+			if (!IsBinaryUpgrade)
+			{
+				char *langtag = icu_language_tag(colliculocale,
+												 icu_validation_level);
+
+				if (langtag && strcmp(colliculocale, langtag) != 0)
+				{
+					ereport(NOTICE,
+							(errmsg("using standard form \"%s\" for locale \"%s\"",
+									langtag, colliculocale)));
+
+					colliculocale = langtag;
+				}
+			}
+
 			icu_validate_locale(colliculocale);
 		}
 
@@ -570,26 +594,6 @@ cmpaliases(const void *a, const void *b)
 
 #ifdef USE_ICU
 /*
- * Get the ICU language tag for a locale name.
- * The result is a palloc'd string.
- */
-static char *
-get_icu_language_tag(const char *localename)
-{
-	char		buf[ULOC_FULLNAME_CAPACITY];
-	UErrorCode	status;
-
-	status = U_ZERO_ERROR;
-	uloc_toLanguageTag(localename, buf, sizeof(buf), true, &status);
-	if (U_FAILURE(status))
-		ereport(ERROR,
-				(errmsg("could not convert locale name \"%s\" to language tag: %s",
-						localename, u_errorName(status))));
-
-	return pstrdup(buf);
-}
-
-/*
  * Get a comment (specifically, the display name) for an ICU locale.
  * The result is a palloc'd string, or NULL if we can't get a comment
  * or find that it's not all ASCII.  (We can *not* accept non-ASCII
@@ -950,7 +954,7 @@ pg_import_system_collations(PG_FUNCTION_ARGS)
 			else
 				name = uloc_getAvailable(i);
 
-			langtag = get_icu_language_tag(name);
+			langtag = icu_language_tag(name, ERROR);
 
 			/*
 			 * Be paranoid about not allowing any non-ASCII strings into