Introduce "builtin" collation provider.

New provider for collations, like "libc" or "icu", but without any
external dependency.

Initially, the only locale supported by the builtin provider is "C",
which is identical to the libc provider's "C" locale. The libc
provider's "C" locale has always been treated as a special case that
uses an internal implementation, without using libc at all -- so the
new builtin provider uses the same implementation.

The builtin provider's locale is independent of the server environment
variables LC_COLLATE and LC_CTYPE. Using the builtin provider, the
database collation locale can be "C" while LC_COLLATE and LC_CTYPE are
set to "en_US", which is impossible with the libc provider.

By offering a new builtin provider, it clarifies that the semantics of
a collation using this provider will never depend on libc, and makes
it easier to document the behavior.

Discussion: https://postgr.es/m/ab925f69-5f9d-f85e-b87c-bd2a44798659@joeconway.com
Discussion: https://postgr.es/m/dd9261f4-7a98-4565-93ec-336c1c110d90@manitou-mail.org
Discussion: https://postgr.es/m/ff4c2f2f9c8fc7ca27c1c24ae37ecaeaeaff6b53.camel%40j-davis.com
Reviewed-by: Daniel Vérité, Peter Eisentraut, Jeremy Schneider

1 files changed, 97 insertions, 32 deletions

diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index 0f27d7b14cf..65464fac8e5 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -697,6 +697,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	DefElem    *dtemplate = NULL;
 	DefElem    *dencoding = NULL;
 	DefElem    *dlocale = NULL;
+	DefElem    *dbuiltinlocale = NULL;
 	DefElem    *dcollate = NULL;
 	DefElem    *dctype = NULL;
 	DefElem    *diculocale = NULL;
@@ -712,7 +713,7 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	const char *dbtemplate = NULL;
 	char	   *dbcollate = NULL;
 	char	   *dbctype = NULL;
-	char	   *dblocale = NULL;
+	const char *dblocale = NULL;
 	char	   *dbicurules = NULL;
 	char		dblocprovider = '\0';
 	char	   *canonname;
@@ -761,6 +762,12 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 				errorConflictingDefElem(defel, pstate);
 			dlocale = defel;
 		}
+		else if (strcmp(defel->defname, "builtin_locale") == 0)
+		{
+			if (dbuiltinlocale)
+				errorConflictingDefElem(defel, pstate);
+			dbuiltinlocale = defel;
+		}
 		else if (strcmp(defel->defname, "lc_collate") == 0)
 		{
 			if (dcollate)
@@ -896,7 +903,10 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	{
 		dbcollate = defGetString(dlocale);
 		dbctype = defGetString(dlocale);
+		dblocale = defGetString(dlocale);
 	}
+	if (dbuiltinlocale && dbuiltinlocale->arg)
+		dblocale = defGetString(dbuiltinlocale);
 	if (dcollate && dcollate->arg)
 		dbcollate = defGetString(dcollate);
 	if (dctype && dctype->arg)
@@ -909,7 +919,9 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	{
 		char	   *locproviderstr = defGetString(dlocprovider);
 
-		if (pg_strcasecmp(locproviderstr, "icu") == 0)
+		if (pg_strcasecmp(locproviderstr, "builtin") == 0)
+			dblocprovider = COLLPROVIDER_BUILTIN;
+		else if (pg_strcasecmp(locproviderstr, "icu") == 0)
 			dblocprovider = COLLPROVIDER_ICU;
 		else if (pg_strcasecmp(locproviderstr, "libc") == 0)
 			dblocprovider = COLLPROVIDER_LIBC;
@@ -1026,14 +1038,9 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 		dbctype = src_ctype;
 	if (dblocprovider == '\0')
 		dblocprovider = src_locprovider;
-	if (dblocale == NULL && dblocprovider == COLLPROVIDER_ICU)
-	{
-		if (dlocale && dlocale->arg)
-			dblocale = defGetString(dlocale);
-		else
-			dblocale = src_locale;
-	}
-	if (dbicurules == NULL && dblocprovider == COLLPROVIDER_ICU)
+	if (dblocale == NULL)
+		dblocale = src_locale;
+	if (dbicurules == NULL)
 		dbicurules = src_icurules;
 
 	/* Some encodings are client only */
@@ -1058,7 +1065,42 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 
 	check_encoding_locale_matches(encoding, dbcollate, dbctype);
 
-	if (dblocprovider == COLLPROVIDER_ICU)
+	/* validate provider-specific parameters */
+	if (dblocprovider != COLLPROVIDER_BUILTIN)
+	{
+		if (dbuiltinlocale)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("BUILTIN_LOCALE cannot be specified unless locale provider is builtin")));
+	}
+	else if (dblocprovider != COLLPROVIDER_ICU)
+	{
+		if (diculocale)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("ICU locale cannot be specified unless locale provider is ICU")));
+
+		if (dbicurules)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("ICU rules cannot be specified unless locale provider is ICU")));
+	}
+
+	/* validate and canonicalize locale for the provider */
+	if (dblocprovider == COLLPROVIDER_BUILTIN)
+	{
+		/*
+		 * This would happen if template0 uses the libc provider but the new
+		 * database uses builtin.
+		 */
+		if (!dblocale)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("LOCALE or BUILTIN_LOCALE must be specified")));
+
+		dblocale = builtin_validate_locale(encoding, dblocale);
+	}
+	else if (dblocprovider == COLLPROVIDER_ICU)
 	{
 		if (!(is_encoding_supported_by_icu(encoding)))
 			ereport(ERROR,
@@ -1097,18 +1139,10 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 
 		icu_validate_locale(dblocale);
 	}
-	else
-	{
-		if (dblocale)
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
-					 errmsg("ICU locale cannot be specified unless locale provider is ICU")));
 
-		if (dbicurules)
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
-					 errmsg("ICU rules cannot be specified unless locale provider is ICU")));
-	}
+	/* for libc, locale comes from datcollate and datctype */
+	if (dblocprovider == COLLPROVIDER_LIBC)
+		dblocale = NULL;
 
 	/*
 	 * Check that the new encoding and locale settings match the source
@@ -1195,8 +1229,14 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	if (src_collversion && !dcollversion)
 	{
 		char	   *actual_versionstr;
+		const char *locale;
+
+		if (dblocprovider == COLLPROVIDER_LIBC)
+			locale = dbcollate;
+		else
+			locale = dblocale;
 
-		actual_versionstr = get_collation_actual_version(dblocprovider, dblocprovider == COLLPROVIDER_ICU ? dblocale : dbcollate);
+		actual_versionstr = get_collation_actual_version(dblocprovider, locale);
 		if (!actual_versionstr)
 			ereport(ERROR,
 					(errmsg("template database \"%s\" has a collation version, but no actual collation version could be determined",
@@ -1224,7 +1264,16 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	 * collation version, which is normally only the case for template0.
 	 */
 	if (dbcollversion == NULL)
-		dbcollversion = get_collation_actual_version(dblocprovider, dblocprovider == COLLPROVIDER_ICU ? dblocale : dbcollate);
+	{
+		const char *locale;
+
+		if (dblocprovider == COLLPROVIDER_LIBC)
+			locale = dbcollate;
+		else
+			locale = dblocale;
+
+		dbcollversion = get_collation_actual_version(dblocprovider, locale);
+	}
 
 	/* Resolve default tablespace for new database */
 	if (dtablespacename && dtablespacename->arg)
@@ -1363,8 +1412,8 @@ createdb(ParseState *pstate, const CreatedbStmt *stmt)
 	 * block on the unique index, and fail after we commit).
 	 */
 
-	Assert((dblocprovider == COLLPROVIDER_ICU && dblocale) ||
-		   (dblocprovider != COLLPROVIDER_ICU && !dblocale));
+	Assert((dblocprovider != COLLPROVIDER_LIBC && dblocale) ||
+		   (dblocprovider == COLLPROVIDER_LIBC && !dblocale));
 
 	/* Form tuple */
 	new_record[Anum_pg_database_oid - 1] = ObjectIdGetDatum(dboid);
@@ -2471,10 +2520,21 @@ AlterDatabaseRefreshColl(AlterDatabaseRefreshCollStmt *stmt)
 	datum = heap_getattr(tuple, Anum_pg_database_datcollversion, RelationGetDescr(rel), &isnull);
 	oldversion = isnull ? NULL : TextDatumGetCString(datum);
 
-	datum = heap_getattr(tuple, datForm->datlocprovider == COLLPROVIDER_ICU ? Anum_pg_database_datlocale : Anum_pg_database_datcollate, RelationGetDescr(rel), &isnull);
-	if (isnull)
-		elog(ERROR, "unexpected null in pg_database");
-	newversion = get_collation_actual_version(datForm->datlocprovider, TextDatumGetCString(datum));
+	if (datForm->datlocprovider == COLLPROVIDER_LIBC)
+	{
+		datum = heap_getattr(tuple, Anum_pg_database_datcollate, RelationGetDescr(rel), &isnull);
+		if (isnull)
+			elog(ERROR, "unexpected null in pg_database");
+	}
+	else
+	{
+		datum = heap_getattr(tuple, Anum_pg_database_datlocale, RelationGetDescr(rel), &isnull);
+		if (isnull)
+			elog(ERROR, "unexpected null in pg_database");
+	}
+
+	newversion = get_collation_actual_version(datForm->datlocprovider,
+											  TextDatumGetCString(datum));
 
 	/* cannot change from NULL to non-NULL or vice versa */
 	if ((!oldversion && newversion) || (oldversion && !newversion))
@@ -2669,8 +2729,13 @@ pg_database_collation_actual_version(PG_FUNCTION_ARGS)
 
 	datlocprovider = ((Form_pg_database) GETSTRUCT(tp))->datlocprovider;
 
-	datum = SysCacheGetAttrNotNull(DATABASEOID, tp, datlocprovider == COLLPROVIDER_ICU ? Anum_pg_database_datlocale : Anum_pg_database_datcollate);
-	version = get_collation_actual_version(datlocprovider, TextDatumGetCString(datum));
+	if (datlocprovider == COLLPROVIDER_LIBC)
+		datum = SysCacheGetAttrNotNull(DATABASEOID, tp, Anum_pg_database_datcollate);
+	else
+		datum = SysCacheGetAttrNotNull(DATABASEOID, tp, Anum_pg_database_datlocale);
+
+	version = get_collation_actual_version(datlocprovider,
+										   TextDatumGetCString(datum));
 
 	ReleaseSysCache(tp);