More sensible character_octet_length

For character types with typmod, character_octet_length columns in the
information schema now show the maximum character length times the
maximum length of a character in the server encoding, instead of some
huge value as before.

6 files changed, 31 insertions, 12 deletions

diff --git a/doc/src/sgml/information_schema.sgml b/doc/src/sgml/information_schema.sgml
index 8e145d7ef1..6460862cfb 100644
--- a/doc/src/sgml/information_schema.sgml
+++ b/doc/src/sgml/information_schema.sgml
@@ -343,10 +343,10 @@
       <entry><type>cardinal_number</type></entry>
       <entry>
        If <literal>data_type</literal> identifies a character type,
-       the maximum possible length in octets (bytes) of a datum (this
-       should not be of concern to
-       <productname>PostgreSQL</productname> users); null for all
-       other data types.
+       the maximum possible length in octets (bytes) of a datum; null
+       for all other data types.  The maximum octet length depends on
+       the declared character maximum length (see above) and the
+       server encoding.
       </entry>
      </row>
 
@@ -947,9 +947,10 @@
       <entry><type>cardinal_number</type></entry>
       <entry>
        If <literal>data_type</literal> identifies a character type,
-       the maximum possible length in octets (bytes) of a datum (this
-       should not be of concern to <productname>PostgreSQL</productname> users); null for all
-       other data types.
+       the maximum possible length in octets (bytes) of a datum; null
+       for all other data types.  The maximum octet length depends on
+       the declared character maximum length (see above) and the
+       server encoding.
       </entry>
      </row>
 
@@ -1688,9 +1689,9 @@
       <entry><type>cardinal_number</type></entry>
       <entry>
        If the domain has a character type, the maximum possible length
-       in octets (bytes) of a datum (this should not be of concern to
-       <productname>PostgreSQL</productname> users); null for all
-       other data types.
+       in octets (bytes) of a datum; null for all other data types.
+       The maximum octet length depends on the declared character
+       maximum length (see above) and the server encoding.
       </entry>
      </row>
 
diff --git a/src/backend/catalog/information_schema.sql b/src/backend/catalog/information_schema.sql
index fe753221c6..27a15c9c97 100644
--- a/src/backend/catalog/information_schema.sql
+++ b/src/backend/catalog/information_schema.sql
@@ -104,7 +104,10 @@ CREATE FUNCTION _pg_char_octet_length(typid oid, typmod int4) RETURNS integer
     AS
 $$SELECT
   CASE WHEN $1 IN (25, 1042, 1043) /* text, char, varchar */
-       THEN CAST(2^30 AS integer)
+       THEN CASE WHEN $2 = -1 /* default typmod */
+                 THEN CAST(2^30 AS integer)
+                 ELSE information_schema._pg_char_max_length($1, $2) * pg_catalog.pg_encoding_max_length((SELECT encoding FROM pg_database WHERE datname = current_database()))
+            END
        ELSE null
   END$$;
 
diff --git a/src/backend/utils/mb/mbutils.c b/src/backend/utils/mb/mbutils.c
index 753c927df3..058493ca37 100644
--- a/src/backend/utils/mb/mbutils.c
+++ b/src/backend/utils/mb/mbutils.c
@@ -482,6 +482,17 @@ length_in_encoding(PG_FUNCTION_ARGS)
 
 }
 
+Datum
+pg_encoding_max_length_sql(PG_FUNCTION_ARGS)
+{
+	int encoding = PG_GETARG_INT32(0);
+
+	if (PG_VALID_ENCODING(encoding))
+		return pg_wchar_table[encoding].maxmblen;
+	else
+		PG_RETURN_NULL();
+}
+
 /*
  * convert client encoding to server encoding.
  */
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 1e742511e4..98eba9b699 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200904091
+#define CATALOG_VERSION_NO	200907071
 
 #endif
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 0285acd154..e194d6a91d 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -2278,6 +2278,9 @@ DESCR("convert encoding name to encoding id");
 DATA(insert OID = 1597 (  pg_encoding_to_char	   PGNSP PGUID 12 1 0 0 f f f t f s 1 0 19 "23" _null_ _null_ _null_ _null_ PG_encoding_to_char _null_ _null_ _null_ ));
 DESCR("convert encoding id to encoding name");
 
+DATA(insert OID = 2319 (  pg_encoding_max_length   PGNSP PGUID 12 1 0 0 f f f t f i 1 0 23 "23" _null_ _null_ _null_ _null_ pg_encoding_max_length_sql _null_ _null_ _null_ ));
+DESCR("maximum octet length of a character in an eocidng");
+
 DATA(insert OID = 1638 (  oidgt				   PGNSP PGUID 12 1 0 0 f f f t f i 2 0 16 "26 26" _null_ _null_ _null_ _null_ oidgt _null_ _null_ _null_ ));
 DESCR("greater-than");
 DATA(insert OID = 1639 (  oidge				   PGNSP PGUID 12 1 0 0 f f f t f i 2 0 16 "26 26" _null_ _null_ _null_ _null_ oidge _null_ _null_ _null_ ));
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index c1b93932ee..13fd41a9bc 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -948,6 +948,7 @@ extern Datum pg_convert(PG_FUNCTION_ARGS);
 extern Datum pg_convert_to(PG_FUNCTION_ARGS);
 extern Datum pg_convert_from(PG_FUNCTION_ARGS);
 extern Datum length_in_encoding(PG_FUNCTION_ARGS);
+extern Datum pg_encoding_max_length_sql(PG_FUNCTION_ARGS);
 
 /* format_type.c */
 extern Datum format_type(PG_FUNCTION_ARGS);