Avoid producing over-length specific_name outputs in information_schema.

information_schema output columns that are declared as being type
sql_identifier are supposed to conform to the implementation's rules
for valid identifiers, in particular the identifier length limit.
Several places potentially violated this limit by concatenating a
function's name and OID.  (The OID is added to ensure name uniqueness
within a schema, since the spec doesn't expect function name overloading.)

Simply truncating the concatenation result to fit in "name" won't do,
since losing part of the OID might wind up giving non-unique results.
Instead, let's truncate the function name as necessary.

The most practical way to do that is to do it in a C function; the
information_schema.sql script doesn't have easy access to the value
of NAMEDATALEN, nor does it have an easy way to truncate on the basis
of resulting byte-length rather than number of characters.

(There are still a couple of places that cast concatenation results to
sql_identifier, but as far as I can see they are guaranteed not to produce
over-length strings, at least with the normal value of NAMEDATALEN.)

Discussion: https://postgr.es/m/23817.1545283477@sss.pgh.pa.us

src/backend/catalog/information_schema.sql

@@ -416,7 +416,7 @@ CREATE VIEW check_constraint_routine_usage AS
            CAST(c.conname AS sql_identifier) AS constraint_name,
            CAST(current_database() AS sql_identifier) AS specific_catalog,
            CAST(np.nspname AS sql_identifier) AS specific_schema,
-           CAST(p.proname || '_' || CAST(p.oid AS text) AS sql_identifier) AS specific_name
+           CAST(nameconcatoid(p.proname, p.oid) AS sql_identifier) AS specific_name
     FROM pg_namespace nc, pg_constraint c, pg_depend d, pg_proc p, pg_namespace np
     WHERE nc.oid = c.connamespace
       AND c.contype = 'c'
@@ -1115,7 +1115,7 @@ GRANT SELECT ON key_column_usage TO PUBLIC;
 CREATE VIEW parameters AS
     SELECT CAST(current_database() AS sql_identifier) AS specific_catalog,
            CAST(n_nspname AS sql_identifier) AS specific_schema,
-           CAST(proname || '_' || CAST(p_oid AS text) AS sql_identifier) AS specific_name,
+           CAST(nameconcatoid(proname, p_oid) AS sql_identifier) AS specific_name,
            CAST((ss.x).n AS cardinal_number) AS ordinal_position,
            CAST(
              CASE WHEN proargmodes IS NULL THEN 'IN'
@@ -1320,7 +1320,7 @@ CREATE VIEW routine_privileges AS
            CAST(grantee.rolname AS sql_identifier) AS grantee,
            CAST(current_database() AS sql_identifier) AS specific_catalog,
            CAST(n.nspname AS sql_identifier) AS specific_schema,
-           CAST(p.proname || '_' || CAST(p.oid AS text) AS sql_identifier) AS specific_name,
+           CAST(nameconcatoid(p.proname, p.oid) AS sql_identifier) AS specific_name,
            CAST(current_database() AS sql_identifier) AS routine_catalog,
            CAST(n.nspname AS sql_identifier) AS routine_schema,
            CAST(p.proname AS sql_identifier) AS routine_name,
@@ -1409,7 +1409,7 @@ GRANT SELECT ON role_routine_grants TO PUBLIC;
 CREATE VIEW routines AS
     SELECT CAST(current_database() AS sql_identifier) AS specific_catalog,
            CAST(n.nspname AS sql_identifier) AS specific_schema,
-           CAST(p.proname || '_' || CAST(p.oid AS text) AS sql_identifier) AS specific_name,
+           CAST(nameconcatoid(p.proname, p.oid) AS sql_identifier) AS specific_name,
            CAST(current_database() AS sql_identifier) AS routine_catalog,
            CAST(n.nspname AS sql_identifier) AS routine_schema,
            CAST(p.proname AS sql_identifier) AS routine_name,
@@ -1964,7 +1964,7 @@ CREATE VIEW transforms AS
            CAST(t.typname AS sql_identifier) AS udt_name,
            CAST(current_database() AS sql_identifier) AS specific_catalog,
            CAST(np.nspname AS sql_identifier) AS specific_schema,
-           CAST(p.proname || '_' || CAST(p.oid AS text) AS sql_identifier) AS specific_name,
+           CAST(nameconcatoid(p.proname, p.oid) AS sql_identifier) AS specific_name,
            CAST(l.lanname AS sql_identifier) AS group_name,
            CAST('FROM SQL' AS character_data) AS transform_type
     FROM pg_type t JOIN pg_transform x ON t.oid = x.trftype
@@ -1980,7 +1980,7 @@ CREATE VIEW transforms AS
            CAST(t.typname AS sql_identifier) AS udt_name,
            CAST(current_database() AS sql_identifier) AS specific_catalog,
            CAST(np.nspname AS sql_identifier) AS specific_schema,
-           CAST(p.proname || '_' || CAST(p.oid AS text) AS sql_identifier) AS specific_name,
+           CAST(nameconcatoid(p.proname, p.oid) AS sql_identifier) AS specific_name,
            CAST(l.lanname AS sql_identifier) AS group_name,
            CAST('TO SQL' AS character_data) AS transform_type
     FROM pg_type t JOIN pg_transform x ON t.oid = x.trftype
@@ -2495,7 +2495,7 @@ CREATE VIEW view_routine_usage AS
            CAST(v.relname AS sql_identifier) AS table_name,
            CAST(current_database() AS sql_identifier) AS specific_catalog,
            CAST(np.nspname AS sql_identifier) AS specific_schema,
-           CAST(p.proname || '_' || CAST(p.oid AS text)  AS sql_identifier) AS specific_name
+           CAST(nameconcatoid(p.proname, p.oid) AS sql_identifier) AS specific_name
 
     FROM pg_namespace nv, pg_class v, pg_depend dv,
          pg_depend dp, pg_proc p, pg_namespace np
@@ -2712,7 +2712,8 @@ CREATE VIEW element_types AS
            UNION ALL
 
            /* parameters */
-           SELECT pronamespace, CAST(proname || '_' || CAST(oid AS text) AS sql_identifier),
+           SELECT pronamespace,
+                  CAST(nameconcatoid(proname, oid) AS sql_identifier),
                   'ROUTINE'::text, (ss.x).n, (ss.x).x, 0
            FROM (SELECT p.pronamespace, p.proname, p.oid,
                         _pg_expandarray(coalesce(p.proallargtypes, p.proargtypes::oid[])) AS x
@@ -2721,7 +2722,8 @@ CREATE VIEW element_types AS
            UNION ALL
 
            /* result types */
-           SELECT p.pronamespace, CAST(p.proname || '_' || CAST(p.oid AS text) AS sql_identifier),
+           SELECT p.pronamespace,
+                  CAST(nameconcatoid(p.proname, p.oid) AS sql_identifier),
                   'ROUTINE'::text, 0, p.prorettype, 0
            FROM pg_proc p
 

src/backend/utils/adt/name.c

@@ -364,3 +364,38 @@ current_schemas(PG_FUNCTION_ARGS)
 
 	PG_RETURN_POINTER(array);
 }
+
+/*
+ * SQL-function nameconcatoid(name, oid) returns name
+ *
+ * This is used in the information_schema to produce specific_name columns,
+ * which are supposed to be unique per schema.  We achieve that (in an ugly
+ * way) by appending the object's OID.  The result is the same as
+ *		($1::text || '_' || $2::text)::name
+ * except that, if it would not fit in NAMEDATALEN, we make it do so by
+ * truncating the name input (not the oid).
+ */
+Datum
+nameconcatoid(PG_FUNCTION_ARGS)
+{
+	Name		nam = PG_GETARG_NAME(0);
+	Oid			oid = PG_GETARG_OID(1);
+	Name		result;
+	char		suffix[20];
+	int			suflen;
+	int			namlen;
+
+	suflen = snprintf(suffix, sizeof(suffix), "_%u", oid);
+	namlen = strlen(NameStr(*nam));
+
+	/* Truncate oversize input by truncating name part, not suffix */
+	if (namlen + suflen >= NAMEDATALEN)
+		namlen = pg_mbcliplen(NameStr(*nam), namlen, NAMEDATALEN - 1 - suflen);
+
+	/* We use palloc0 here to ensure result is zero-padded */
+	result = (Name) palloc0(NAMEDATALEN);
+	memcpy(NameStr(*result), NameStr(*nam), namlen);
+	memcpy(NameStr(*result) + namlen, suffix, suflen);
+
+	PG_RETURN_NAME(result);
+}

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201812192
+#define CATALOG_VERSION_NO	201812201
 
 #endif

src/include/catalog/pg_proc.dat

@@ -716,6 +716,10 @@
   proname => 'bttextnamecmp', proleakproof => 't', prorettype => 'int4',
   proargtypes => 'text name', prosrc => 'bttextnamecmp' },
 
+{ oid => '266', descr => 'concatenate name and oid',
+  proname => 'nameconcatoid', prorettype => 'name', proargtypes => 'name oid',
+  prosrc => 'nameconcatoid' },
+
 { oid => '274',
   descr => 'current date and time - increments during transactions',
   proname => 'timeofday', provolatile => 'v', prorettype => 'text',