Don't set a fast default for anything but a plain table

The fast default code added in Release 11 omitted to check that the
table a fast default was being added to was a plain table. Thus one
could be added to a foreign table, which predicably blows up. Here we
perform that check.

In addition, on the back branches, since some of these might have
escaped into the wild, if we encounter a missing value for
an attribute of something other than a plain table we ignore it.

Fixes bug #17056

Backpatch to release 11,

Reviewed by: Andres Freund, Álvaro Herrera and Tom Lane

1 files changed, 18 insertions, 1 deletions

diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index 2babf525380..be50de462ed 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -552,6 +552,7 @@ RelationBuildTupleDesc(Relation relation)
 	{
 		Form_pg_attribute attp;
 		int			attnum;
+		bool        atthasmissing;
 
 		attp = (Form_pg_attribute) GETSTRUCT(pg_attribute_tuple);
 
@@ -565,6 +566,22 @@ RelationBuildTupleDesc(Relation relation)
 			   attp,
 			   ATTRIBUTE_FIXED_PART_SIZE);
 
+		/*
+		 * Fix atthasmissing flag - it's only for plain tables. Others
+		 * should not have missing values set, but there may be some left from
+		 * before when we placed that check, so this code defensively ignores
+		 * such values.
+		 */
+		atthasmissing = attp->atthasmissing;
+		if (relation->rd_rel->relkind != RELKIND_RELATION && atthasmissing)
+		{
+			Form_pg_attribute nattp;
+
+			atthasmissing = false;
+			nattp = TupleDescAttr(relation->rd_att, attnum - 1);
+			nattp->atthasmissing = false;
+		}
+
 		/* Update constraint/default info */
 		if (attp->attnotnull)
 			constr->has_not_null = true;
@@ -586,7 +603,7 @@ RelationBuildTupleDesc(Relation relation)
 		}
 
 		/* Likewise for a missing value */
-		if (attp->atthasmissing)
+		if (atthasmissing)
 		{
 			Datum		missingval;
 			bool		missingNull;