get_relid_attribute_name is dead, long live get_attname

The modern way is to use a missing_ok argument instead of two separate
almost-identical routines, so do that.

Author: Michaël Paquier
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/20180201063212.GE6398@paquier.xyz

contrib/postgres_fdw/deparse.c

@@ -2176,7 +2176,7 @@ deparseColumnRef(StringInfo buf, int varno, int varattno, PlannerInfo *root,
 		 * FDW option, use attribute name.
 		 */
 		if (colname == NULL)
-			colname = get_relid_attribute_name(rte->relid, varattno);
+			colname = get_attname(rte->relid, varattno, false);
 
 		if (qualify_col)
 			ADD_REL_QUALIFIER(buf, varno);

contrib/postgres_fdw/postgres_fdw.c

@@ -5545,7 +5545,7 @@ conversion_error_callback(void *arg)
 			if (var->varattno == 0)
 				is_wholerow = true;
 			else
-				attname = get_relid_attribute_name(rte->relid, var->varattno);
+				attname = get_attname(rte->relid, var->varattno, false);
 
 			relname = get_rel_name(rte->relid);
 		}

contrib/sepgsql/dml.c

@@ -118,10 +118,7 @@ fixup_inherited_columns(Oid parentId, Oid childId, Bitmapset *columns)
 			continue;
 		}
 
-		attname = get_attname(parentId, attno);
+		attname = get_attname(parentId, attno, false);
-		if (!attname)
-			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
-				 attno, parentId);
 		attno = get_attnum(childId, attname);
 		if (attno == InvalidAttrNumber)
 			elog(ERROR, "cache lookup failed for attribute %s of relation %u",

src/backend/catalog/heap.c

@@ -2405,7 +2405,8 @@ AddRelationNewConstraints(Relation rel,
 
 			if (list_length(vars) == 1)
 				colname = get_attname(RelationGetRelid(rel),
-									  ((Var *) linitial(vars))->varattno);
+									  ((Var *) linitial(vars))->varattno,
+									  true);
 			else
 				colname = NULL;
 

src/backend/catalog/objectaddress.c

@@ -2682,8 +2682,9 @@ getObjectDescription(const ObjectAddress *object)
 			getRelationDescription(&buffer, object->objectId);
 			if (object->objectSubId != 0)
 				appendStringInfo(&buffer, _(" column %s"),
-								 get_relid_attribute_name(object->objectId,
+								 get_attname(object->objectId,
-														  object->objectSubId));
+											 object->objectSubId,
+											 false));
 			break;
 
 		case OCLASS_PROC:
@@ -4103,8 +4104,8 @@ getObjectIdentityParts(const ObjectAddress *object,
 			{
 				char	   *attr;
 
-				attr = get_relid_attribute_name(object->objectId,
+				attr = get_attname(object->objectId, object->objectSubId,
-												object->objectSubId);
+								   false);
 				appendStringInfo(&buffer, ".%s", quote_identifier(attr));
 				if (objname)
 					*objname = lappend(*objname, attr);

src/backend/parser/parse_relation.c

@@ -2687,7 +2687,7 @@ get_rte_attribute_name(RangeTblEntry *rte, AttrNumber attnum)
 	 * built (which can easily happen for rules).
 	 */
 	if (rte->rtekind == RTE_RELATION)
-		return get_relid_attribute_name(rte->relid, attnum);
+		return get_attname(rte->relid, attnum, false);
 
 	/*
 	 * Otherwise use the column name from eref.  There should always be one.

src/backend/parser/parse_utilcmd.c

@@ -1470,7 +1470,7 @@ generateClonedIndexStmt(RangeVar *heapRel, Oid heapRelid, Relation source_idx,
 			/* Simple index column */
 			char	   *attname;
 
-			attname = get_relid_attribute_name(indrelid, attnum);
+			attname = get_attname(indrelid, attnum, false);
 			keycoltype = get_atttype(indrelid, attnum);
 
 			iparam->name = attname;
@@ -3406,8 +3406,8 @@ transformPartitionBound(ParseState *pstate, Relation parent,
 
 		/* Get the only column's name in case we need to output an error */
 		if (key->partattrs[0] != 0)
-			colname = get_relid_attribute_name(RelationGetRelid(parent),
+			colname = get_attname(RelationGetRelid(parent),
-											   key->partattrs[0]);
+								  key->partattrs[0], false);
 		else
 			colname = deparse_expression((Node *) linitial(partexprs),
 										 deparse_context_for(RelationGetRelationName(parent),
@@ -3491,8 +3491,8 @@ transformPartitionBound(ParseState *pstate, Relation parent,
 
 			/* Get the column's name in case we need to output an error */
 			if (key->partattrs[i] != 0)
-				colname = get_relid_attribute_name(RelationGetRelid(parent),
+				colname = get_attname(RelationGetRelid(parent),
-												   key->partattrs[i]);
+									  key->partattrs[i], false);
 			else
 			{
 				colname = deparse_expression((Node *) list_nth(partexprs, j),

src/backend/utils/adt/ruleutils.c

@@ -908,8 +908,8 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
 
 				if (i > 0)
 					appendStringInfoString(&buf, ", ");
-				attname = get_relid_attribute_name(trigrec->tgrelid,
+				attname = get_attname(trigrec->tgrelid,
-												   trigrec->tgattr.values[i]);
+									  trigrec->tgattr.values[i], false);
 				appendStringInfoString(&buf, quote_identifier(attname));
 			}
 		}
@@ -1292,7 +1292,7 @@ pg_get_indexdef_worker(Oid indexrelid, int colno,
 			char	   *attname;
 			int32		keycoltypmod;
 
-			attname = get_relid_attribute_name(indrelid, attnum);
+			attname = get_attname(indrelid, attnum, false);
 			if (!colno || colno == keyno + 1)
 				appendStringInfoString(&buf, quote_identifier(attname));
 			get_atttypetypmodcoll(indrelid, attnum,
@@ -1535,7 +1535,7 @@ pg_get_statisticsobj_worker(Oid statextid, bool missing_ok)
 		if (colno > 0)
 			appendStringInfoString(&buf, ", ");
 
-		attname = get_relid_attribute_name(statextrec->stxrelid, attnum);
+		attname = get_attname(statextrec->stxrelid, attnum, false);
 
 		appendStringInfoString(&buf, quote_identifier(attname));
 	}
@@ -1692,7 +1692,7 @@ pg_get_partkeydef_worker(Oid relid, int prettyFlags,
 			char	   *attname;
 			int32		keycoltypmod;
 
-			attname = get_relid_attribute_name(relid, attnum);
+			attname = get_attname(relid, attnum, false);
 			appendStringInfoString(&buf, quote_identifier(attname));
 			get_atttypetypmodcoll(relid, attnum,
 								  &keycoltype, &keycoltypmod,
@@ -2196,7 +2196,7 @@ decompile_column_index_array(Datum column_index_array, Oid relId,
 	{
 		char	   *colName;
 
-		colName = get_relid_attribute_name(relId, DatumGetInt16(keys[j]));
+		colName = get_attname(relId, DatumGetInt16(keys[j]), false);
 
 		if (j == 0)
 			appendStringInfoString(buf, quote_identifier(colName));
@@ -6015,8 +6015,9 @@ get_insert_query_def(Query *query, deparse_context *context)
 		 * tle->resname, since resname will fail to track RENAME.
 		 */
 		appendStringInfoString(buf,
-							   quote_identifier(get_relid_attribute_name(rte->relid,
+							   quote_identifier(get_attname(rte->relid,
-																		 tle->resno)));
+															tle->resno,
+															false)));
 
 		/*
 		 * Print any indirection needed (subfields or subscripts), and strip
@@ -6319,8 +6320,9 @@ get_update_query_targetlist_def(Query *query, List *targetList,
 		 * tle->resname, since resname will fail to track RENAME.
 		 */
 		appendStringInfoString(buf,
-							   quote_identifier(get_relid_attribute_name(rte->relid,
+							   quote_identifier(get_attname(rte->relid,
-																		 tle->resno)));
+															tle->resno,
+															false)));
 
 		/*
 		 * Print any indirection needed (subfields or subscripts), and strip
@@ -10340,8 +10342,8 @@ processIndirection(Node *node, deparse_context *context)
 			 * target lists, but this function cannot be used for that case.
 			 */
 			Assert(list_length(fstore->fieldnums) == 1);
-			fieldname = get_relid_attribute_name(typrelid,
+			fieldname = get_attname(typrelid,
-												 linitial_int(fstore->fieldnums));
+									linitial_int(fstore->fieldnums), false);
 			appendStringInfo(buf, ".%s", quote_identifier(fieldname));
 
 			/*

src/backend/utils/cache/lsyscache.c

@@ -765,19 +765,19 @@ get_opfamily_proc(Oid opfamily, Oid lefttype, Oid righttype, int16 procnum)
 
 /*
  * get_attname
- *		Given the relation id and the attribute number,
+ *		Given the relation id and the attribute number, return the "attname"
- *		return the "attname" field from the attribute relation.
+ *		field from the attribute relation as a palloc'ed string.
  *
- * Note: returns a palloc'd copy of the string, or NULL if no such attribute.
+ * If no such attribute exists and missing_ok is true, NULL is returned;
+ * otherwise a not-intended-for-user-consumption error is thrown.
  */
 char *
-get_attname(Oid relid, AttrNumber attnum)
+get_attname(Oid relid, AttrNumber attnum, bool missing_ok)
 {
 	HeapTuple	tp;
 
 	tp = SearchSysCache2(ATTNUM,
-						 ObjectIdGetDatum(relid),
+						 ObjectIdGetDatum(relid), Int16GetDatum(attnum));
-						 Int16GetDatum(attnum));
 	if (HeapTupleIsValid(tp))
 	{
 		Form_pg_attribute att_tup = (Form_pg_attribute) GETSTRUCT(tp);
@@ -787,26 +787,11 @@ get_attname(Oid relid, AttrNumber attnum)
 		ReleaseSysCache(tp);
 		return result;
 	}
-	else
-		return NULL;
-}
 
-/*
+	if (!missing_ok)
- * get_relid_attribute_name
- *
- * Same as above routine get_attname(), except that error
- * is handled by elog() instead of returning NULL.
- */
-char *
-get_relid_attribute_name(Oid relid, AttrNumber attnum)
-{
-	char	   *attname;
-
-	attname = get_attname(relid, attnum);
-	if (attname == NULL)
 		elog(ERROR, "cache lookup failed for attribute %d of relation %u",
 			 attnum, relid);
-	return attname;
+	return NULL;
 }
 
 /*

src/backend/utils/cache/relcache.c

@@ -5250,7 +5250,7 @@ errtablecol(Relation rel, int attnum)
 	if (attnum > 0 && attnum <= reldesc->natts)
 		colname = NameStr(TupleDescAttr(reldesc, attnum - 1)->attname);
 	else
-		colname = get_relid_attribute_name(RelationGetRelid(rel), attnum);
+		colname = get_attname(RelationGetRelid(rel), attnum, false);
 
 	return errtablecolname(rel, colname);
 }

src/include/utils/lsyscache.h

@@ -83,8 +83,7 @@ extern List *get_op_btree_interpretation(Oid opno);
 extern bool equality_ops_are_compatible(Oid opno1, Oid opno2);
 extern Oid get_opfamily_proc(Oid opfamily, Oid lefttype, Oid righttype,
 				  int16 procnum);
-extern char *get_attname(Oid relid, AttrNumber attnum);
+extern char *get_attname(Oid relid, AttrNumber attnum, bool missing_ok);
-extern char *get_relid_attribute_name(Oid relid, AttrNumber attnum);
 extern AttrNumber get_attnum(Oid relid, const char *attname);
 extern char get_attidentity(Oid relid, AttrNumber attnum);
 extern Oid	get_atttype(Oid relid, AttrNumber attnum);