Add function to import operating system collations

Move this logic out of initdb into a user-callable function.  This
simplifies the code and makes it possible to update the standard
collations later on if additional operating system collations appear.

Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Euler Taveira <euler@timbira.com.br>

Author: petere

doc/src/sgml/charset.sgml

@@ -496,7 +496,7 @@ SELECT * FROM test1 ORDER BY a || b COLLATE "fr_FR";
    </para>
   </sect2>
 
-  <sect2>
+  <sect2 id="collation-managing">
    <title>Managing Collations</title>
 
    <para>

doc/src/sgml/func.sgml

@@ -19190,6 +19190,46 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
     in the database's default tablespace, the tablespace can be specified as 0.
    </para>
 
+   <para>
+    <xref linkend="functions-admin-collation"> lists functions used to manage
+    collations.
+   </para>
+
+   <table id="functions-admin-collation">
+    <title>Collation Management Functions</title>
+    <tgroup cols="3">
+     <thead>
+      <row><entry>Name</entry> <entry>Return Type</entry> <entry>Description</entry></row>
+     </thead>
+
+     <tbody>
+      <row>
+       <entry>
+        <indexterm><primary>pg_import_system_collations</primary></indexterm>
+        <literal><function>pg_import_system_collations(<parameter>if_not_exists</> <type>boolean</>, <parameter>schema</> <type>regnamespace</>)</function></literal>
+       </entry>
+       <entry><type>void</type></entry>
+       <entry>Import operating system collations</entry>
+      </row>
+     </tbody>
+    </tgroup>
+   </table>
+
+   <para>
+    <function>pg_import_system_collations</> populates the system
+    catalog <literal>pg_collation</literal> with collations based on all the
+    locales it finds on the operating system.  This is
+    what <command>initdb</command> uses;
+    see <xref linkend="collation-managing"> for more details.  If additional
+    locales are installed into the operating system later on, this function
+    can be run again to add collations for the new locales.  In that case, the
+    parameter <parameter>if_not_exists</parameter> should be set to true to
+    skip over existing collations.  The <parameter>schema</parameter>
+    parameter would typically be <literal>pg_catalog</literal>, but that is
+    not a requirement.  (Collation objects based on locales that are no longer
+    present on the operating system are never removed by this function.)
+   </para>
+
   </sect2>
 
   <sect2 id="functions-admin-index">

src/backend/catalog/pg_collation.c

@@ -41,7 +41,8 @@ Oid
 CollationCreate(const char *collname, Oid collnamespace,
 				Oid collowner,
 				int32 collencoding,
-				const char *collcollate, const char *collctype)
+				const char *collcollate, const char *collctype,
+				bool if_not_exists)
 {
 	Relation	rel;
 	TupleDesc	tupDesc;
@@ -72,10 +73,21 @@ CollationCreate(const char *collname, Oid collnamespace,
 							  PointerGetDatum(collname),
 							  Int32GetDatum(collencoding),
 							  ObjectIdGetDatum(collnamespace)))
-		ereport(ERROR,
+	{
+		if (if_not_exists)
+		{
+			ereport(NOTICE,
 				(errcode(ERRCODE_DUPLICATE_OBJECT),
-				 errmsg("collation \"%s\" for encoding \"%s\" already exists",
+				 errmsg("collation \"%s\" for encoding \"%s\" already exists, skipping",
 						collname, pg_encoding_to_char(collencoding))));
+			return InvalidOid;
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_DUPLICATE_OBJECT),
+					 errmsg("collation \"%s\" for encoding \"%s\" already exists",
+							collname, pg_encoding_to_char(collencoding))));
+	}
 
 	/*
 	 * Also forbid matching an any-encoding entry.  This test of course is not
@@ -86,10 +98,21 @@ CollationCreate(const char *collname, Oid collnamespace,
 							  PointerGetDatum(collname),
 							  Int32GetDatum(-1),
 							  ObjectIdGetDatum(collnamespace)))
-		ereport(ERROR,
+	{
+		if (if_not_exists)
+		{
+			ereport(NOTICE,
+				(errcode(ERRCODE_DUPLICATE_OBJECT),
+				 errmsg("collation \"%s\" already exists, skipping",
+						collname)));
+			return InvalidOid;
+		}
+		else
+			ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_OBJECT),
 				 errmsg("collation \"%s\" already exists",
 						collname)));
+	}
 
 	/* open pg_collation */
 	rel = heap_open(CollationRelationId, RowExclusiveLock);

src/backend/commands/collationcmds.c

@@ -136,7 +136,11 @@ DefineCollation(ParseState *pstate, List *names, List *parameters)
 							 GetUserId(),
 							 GetDatabaseEncoding(),
 							 collcollate,
-							 collctype);
+							 collctype,
+							 false);
+
+	if (!OidIsValid(newoid))
+		return InvalidObjectAddress;
 
 	ObjectAddressSet(address, CollationRelationId, newoid);
 
@@ -177,3 +181,151 @@ IsThereCollationInNamespace(const char *collname, Oid nspOid)
 				 errmsg("collation \"%s\" already exists in schema \"%s\"",
 						collname, get_namespace_name(nspOid))));
 }
+
+
+/*
+ * "Normalize" a locale name, stripping off encoding tags such as
+ * ".utf8" (e.g., "en_US.utf8" -> "en_US", but "br_FR.iso885915@euro"
+ * -> "br_FR@euro").  Return true if a new, different name was
+ * generated.
+ */
+pg_attribute_unused()
+static bool
+normalize_locale_name(char *new, const char *old)
+{
+	char	   *n = new;
+	const char *o = old;
+	bool		changed = false;
+
+	while (*o)
+	{
+		if (*o == '.')
+		{
+			/* skip over encoding tag such as ".utf8" or ".UTF-8" */
+			o++;
+			while ((*o >= 'A' && *o <= 'Z')
+				   || (*o >= 'a' && *o <= 'z')
+				   || (*o >= '0' && *o <= '9')
+				   || (*o == '-'))
+				o++;
+			changed = true;
+		}
+		else
+			*n++ = *o++;
+	}
+	*n = '\0';
+
+	return changed;
+}
+
+
+Datum
+pg_import_system_collations(PG_FUNCTION_ARGS)
+{
+#if defined(HAVE_LOCALE_T) && !defined(WIN32)
+	bool		if_not_exists = PG_GETARG_BOOL(0);
+	Oid         nspid = PG_GETARG_OID(1);
+
+	FILE	   *locale_a_handle;
+	char		localebuf[NAMEDATALEN]; /* we assume ASCII so this is fine */
+	int			count = 0;
+#endif
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 (errmsg("must be superuser to import system collations"))));
+
+#if defined(HAVE_LOCALE_T) && !defined(WIN32)
+	locale_a_handle = OpenPipeStream("locale -a", "r");
+	if (locale_a_handle == NULL)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not execute command \"%s\": %m",
+						"locale -a")));
+
+	while (fgets(localebuf, sizeof(localebuf), locale_a_handle))
+	{
+		int			i;
+		size_t		len;
+		int			enc;
+		bool		skip;
+		char		alias[NAMEDATALEN];
+
+		len = strlen(localebuf);
+
+		if (len == 0 || localebuf[len - 1] != '\n')
+		{
+			elog(DEBUG1, "locale name too long, skipped: \"%s\"", localebuf);
+			continue;
+		}
+		localebuf[len - 1] = '\0';
+
+		/*
+		 * Some systems have locale names that don't consist entirely of ASCII
+		 * letters (such as "bokm&aring;l" or "fran&ccedil;ais").  This is
+		 * pretty silly, since we need the locale itself to interpret the
+		 * non-ASCII characters. We can't do much with those, so we filter
+		 * them out.
+		 */
+		skip = false;
+		for (i = 0; i < len; i++)
+		{
+			if (IS_HIGHBIT_SET(localebuf[i]))
+			{
+				skip = true;
+				break;
+			}
+		}
+		if (skip)
+		{
+			elog(DEBUG1, "locale name has non-ASCII characters, skipped: \"%s\"", localebuf);
+			continue;
+		}
+
+		enc = pg_get_encoding_from_locale(localebuf, false);
+		if (enc < 0)
+		{
+			/* error message printed by pg_get_encoding_from_locale() */
+			continue;
+		}
+		if (!PG_VALID_BE_ENCODING(enc))
+			continue;			/* ignore locales for client-only encodings */
+		if (enc == PG_SQL_ASCII)
+			continue;			/* C/POSIX are already in the catalog */
+
+		count++;
+
+		CollationCreate(localebuf, nspid, GetUserId(), enc,
+						localebuf, localebuf, if_not_exists);
+
+		CommandCounterIncrement();
+
+		/*
+		 * Generate aliases such as "en_US" in addition to "en_US.utf8" for
+		 * ease of use.  Note that collation names are unique per encoding
+		 * only, so this doesn't clash with "en_US" for LATIN1, say.
+		 *
+		 * This always runs in "if not exists" mode, to skip aliases that
+		 * conflict with an existing locale name for the same encoding.  For
+		 * example, "br_FR.iso88591" is normalized to "br_FR", both for
+		 * encoding LATIN1.  But the unnormalized locale "br_FR" already
+		 * exists for LATIN1.
+		 */
+		if (normalize_locale_name(alias, localebuf))
+		{
+			CollationCreate(alias, nspid, GetUserId(), enc,
+							localebuf, localebuf, true);
+			CommandCounterIncrement();
+		}
+	}
+
+	ClosePipeStream(locale_a_handle);
+
+	if (count == 0)
+		ereport(ERROR,
+				(errmsg("no usable system locales were found")));
+#endif	/* not HAVE_LOCALE_T && not WIN32 */
+
+	PG_RETURN_VOID();
+}