v16-0001-Add-flag-to-format_type_extended-to-enforce-NULL.patch

From 76ef961e02e0276af5516bdce6e0e543526db5b2 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 2 Jul 2019 16:07:06 +0900
Subject: [PATCH v16 1/3] Add flag to format_type_extended to enforce NULL-ness

If a type scanned is undefined, type format routines have two behaviors
depending on if FORMAT_TYPE_ALLOW_INVALID is defined by the caller:
- Generate an error
- Return undefined type name "???" or "-".

The current interface is unhelpful for callers willing to format
properly a type name, but still make sure that the type is defined as
there could be types matching the undefined strings.  In order to
counter that, add a new flag called FORMAT_TYPE_FORCE_NULL which returns
a NULL result instead of "??? or "-" which does not generate an error.
They will be used for future patches to improve the SQL interface for
object addresses.
---
 src/backend/utils/adt/format_type.c | 20 ++++++++++++++++----
 src/include/utils/builtins.h        |  1 +
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/backend/utils/adt/format_type.c b/src/backend/utils/adt/format_type.c
index 6ae2a31345..8ee0e10c29 100644
--- a/src/backend/utils/adt/format_type.c
+++ b/src/backend/utils/adt/format_type.c
@@ -96,6 +96,9 @@ format_type(PG_FUNCTION_ARGS)
  * - FORMAT_TYPE_ALLOW_INVALID
  *			if the type OID is invalid or unknown, return ??? or such instead
  *			of failing
+ * - FORMAT_TYPE_FORCE_NULL
+ *			if the type OID is invalid or unknown, return NULL instead of ???
+ *			or such
  * - FORMAT_TYPE_FORCE_QUALIFY
  *			always schema-qualify type names, regardless of search_path
  *
@@ -114,13 +117,20 @@ format_type_extended(Oid type_oid, int32 typemod, bits16 flags)
 	char	   *buf;
 	bool		with_typemod;
 
-	if (type_oid == InvalidOid && (flags & FORMAT_TYPE_ALLOW_INVALID) != 0)
-		return pstrdup("-");
+	if (type_oid == InvalidOid)
+	{
+		if ((flags & FORMAT_TYPE_FORCE_NULL) != 0)
+			return NULL;
+		else if ((flags & FORMAT_TYPE_ALLOW_INVALID) != 0)
+			return pstrdup("-");
+	}
 
 	tuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(type_oid));
 	if (!HeapTupleIsValid(tuple))
 	{
-		if ((flags & FORMAT_TYPE_ALLOW_INVALID) != 0)
+		if ((flags & FORMAT_TYPE_FORCE_NULL) != 0)
+			return NULL;
+		else if ((flags & FORMAT_TYPE_ALLOW_INVALID) != 0)
 			return pstrdup("???");
 		else
 			elog(ERROR, "cache lookup failed for type %u", type_oid);
@@ -143,7 +153,9 @@ format_type_extended(Oid type_oid, int32 typemod, bits16 flags)
 		tuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(array_base_type));
 		if (!HeapTupleIsValid(tuple))
 		{
-			if ((flags & FORMAT_TYPE_ALLOW_INVALID) != 0)
+			if ((flags & FORMAT_TYPE_FORCE_NULL) != 0)
+				return NULL;
+			else if ((flags & FORMAT_TYPE_ALLOW_INVALID) != 0)
 				return pstrdup("???[]");
 			else
 				elog(ERROR, "cache lookup failed for type %u", type_oid);
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index a3cd7d26fa..a1e418cee7 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -109,6 +109,7 @@ extern Datum numeric_float8_no_overflow(PG_FUNCTION_ARGS);
 #define FORMAT_TYPE_TYPEMOD_GIVEN	0x01	/* typemod defined by caller */
 #define FORMAT_TYPE_ALLOW_INVALID	0x02	/* allow invalid types */
 #define FORMAT_TYPE_FORCE_QUALIFY	0x04	/* force qualification of type */
+#define FORMAT_TYPE_FORCE_NULL		0x08	/* force NULL if undefined */
 extern char *format_type_extended(Oid type_oid, int32 typemod, bits16 flags);
 
 extern char *format_type_be(Oid type_oid);
-- 
2.20.1