Fix handling of CREATE TABLE LIKE with inheritance.

If a CREATE TABLE command uses both LIKE and traditional inheritance,
Vars in CHECK constraints and expression indexes that are absorbed
from a LIKE parent table tended to get mis-numbered, resulting in
wrong answers and/or bizarre error messages (though probably not any
actual crashes, thanks to validation occurring in the executor).

In v12 and up, the same could happen to Vars in GENERATED expressions,
even in cases with no LIKE clause but multiple traditional-inheritance
parents.

The cause of the problem for LIKE is that parse_utilcmd.c supposed
it could renumber such Vars correctly during transformCreateStmt(),
which it cannot since we have not yet accounted for columns added via
inheritance.  Fix that by postponing processing of LIKE INCLUDING
CONSTRAINTS, DEFAULTS, GENERATED, INDEXES till after we've performed
DefineRelation().

The error with GENERATED and multiple inheritance is a simple oversight
in MergeAttributes(); it knows it has to renumber Vars in inherited
CHECK constraints, but forgot to apply the same processing to inherited
GENERATED expressions (a/k/a defaults).

Per bug #16272 from Tom Gottfried.  The non-GENERATED variants of the
issue are ancient, presumably dating right back to the addition of
CREATE TABLE LIKE; hence back-patch to all supported branches.

Discussion: https://postgr.es/m/16272-6e32da020e9a9381@postgresql.org

Author: tglsfdc

src/backend/commands/tablecmds.c

@@ -405,6 +405,8 @@ static bool ConstraintImpliedByRelConstraint(Relation scanrel,
 											 List *testConstraint, List *provenConstraint);
 static ObjectAddress ATExecColumnDefault(Relation rel, const char *colName,
 										 Node *newDefault, LOCKMODE lockmode);
+static ObjectAddress ATExecCookedColumnDefault(Relation rel, AttrNumber attnum,
+											   Node *newDefault);
 static ObjectAddress ATExecAddIdentity(Relation rel, const char *colName,
 									   Node *def, LOCKMODE lockmode);
 static ObjectAddress ATExecSetIdentity(Relation rel, const char *colName,
@@ -2054,8 +2056,8 @@ storage_name(char c)
  * 'schema' is the column/attribute definition for the table. (It's a list
  *		of ColumnDef's.) It is destructively changed.
  * 'supers' is a list of OIDs of parent relations, already locked by caller.
- * 'relpersistence' is a persistence type of the table.
- * 'is_partition' tells if the table is a partition
+ * 'relpersistence' is the persistence type of the table.
+ * 'is_partition' tells if the table is a partition.
  *
  * Output arguments:
  * 'supconstr' receives a list of constraints belonging to the parents,
@@ -2218,7 +2220,11 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 		TupleDesc	tupleDesc;
 		TupleConstr *constr;
 		AttrMap    *newattmap;
+		List	   *inherited_defaults;
+		List	   *cols_with_defaults;
 		AttrNumber	parent_attno;
+		ListCell   *lc1;
+		ListCell   *lc2;
 
 		/* caller already got lock */
 		relation = table_open(parent, NoLock);
@@ -2304,6 +2310,9 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 		 */
 		newattmap = make_attrmap(tupleDesc->natts);
 
+		/* We can't process inherited defaults until newattmap is complete. */
+		inherited_defaults = cols_with_defaults = NIL;
+
 		for (parent_attno = 1; parent_attno <= tupleDesc->natts;
 			 parent_attno++)
 		{
@@ -2359,7 +2368,7 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 									   get_collation_name(defCollId),
 									   get_collation_name(attribute->attcollation))));
 
-				/* Copy storage parameter */
+				/* Copy/check storage parameter */
 				if (def->storage == 0)
 					def->storage = attribute->attstorage;
 				else if (def->storage != attribute->attstorage)
@@ -2410,7 +2419,7 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 			}
 
 			/*
-			 * Copy default if any
+			 * Locate default if any
 			 */
 			if (attribute->atthasdef)
 			{
@@ -2432,23 +2441,59 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 				Assert(this_default != NULL);
 
 				/*
-				 * If default expr could contain any vars, we'd need to fix
-				 * 'em, but it can't; so default is ready to apply to child.
-				 *
-				 * If we already had a default from some prior parent, check
-				 * to see if they are the same.  If so, no problem; if not,
-				 * mark the column as having a bogus default. Below, we will
-				 * complain if the bogus default isn't overridden by the child
-				 * schema.
+				 * If it's a GENERATED default, it might contain Vars that
+				 * need to be mapped to the inherited column(s)' new numbers.
+				 * We can't do that till newattmap is ready, so just remember
+				 * all the inherited default expressions for the moment.
 				 */
-				Assert(def->raw_default == NULL);
-				if (def->cooked_default == NULL)
-					def->cooked_default = this_default;
-				else if (!equal(def->cooked_default, this_default))
-				{
-					def->cooked_default = &bogus_marker;
-					have_bogus_defaults = true;
-				}
+				inherited_defaults = lappend(inherited_defaults, this_default);
+				cols_with_defaults = lappend(cols_with_defaults, def);
+			}
+		}
+
+		/*
+		 * Now process any inherited default expressions, adjusting attnos
+		 * using the completed newattmap map.
+		 */
+		forboth(lc1, inherited_defaults, lc2, cols_with_defaults)
+		{
+			Node	   *this_default = (Node *) lfirst(lc1);
+			ColumnDef  *def = (ColumnDef *) lfirst(lc2);
+			bool		found_whole_row;
+
+			/* Adjust Vars to match new table's column numbering */
+			this_default = map_variable_attnos(this_default,
+											   1, 0,
+											   newattmap,
+											   InvalidOid, &found_whole_row);
+
+			/*
+			 * For the moment we have to reject whole-row variables.  We could
+			 * convert them, if we knew the new table's rowtype OID, but that
+			 * hasn't been assigned yet.  (A variable could only appear in a
+			 * generation expression, so the error message is correct.)
+			 */
+			if (found_whole_row)
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("cannot convert whole-row table reference"),
+						 errdetail("Generation expression for column \"%s\" contains a whole-row reference to table \"%s\".",
+								   def->colname,
+								   RelationGetRelationName(relation))));
+
+			/*
+			 * If we already had a default from some prior parent, check to
+			 * see if they are the same.  If so, no problem; if not, mark the
+			 * column as having a bogus default.  Below, we will complain if
+			 * the bogus default isn't overridden by the child schema.
+			 */
+			Assert(def->raw_default == NULL);
+			if (def->cooked_default == NULL)
+				def->cooked_default = this_default;
+			else if (!equal(def->cooked_default, this_default))
+			{
+				def->cooked_default = &bogus_marker;
+				have_bogus_defaults = true;
 			}
 		}
 
@@ -2667,7 +2712,6 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 					def->raw_default = newdef->raw_default;
 					def->cooked_default = newdef->cooked_default;
 				}
-
 			}
 			else
 			{
@@ -3781,6 +3825,7 @@ AlterTableGetLockLevel(List *cmds)
 				 * Theoretically, these could be ShareRowExclusiveLock.
 				 */
 			case AT_ColumnDefault:
+			case AT_CookedColumnDefault:
 			case AT_AlterConstraint:
 			case AT_AddIndex:	/* from ADD CONSTRAINT */
 			case AT_AddIndexConstraint:
@@ -4040,6 +4085,13 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			/* No command-specific prep needed */
 			pass = cmd->def ? AT_PASS_ADD_OTHERCONSTR : AT_PASS_DROP;
 			break;
+		case AT_CookedColumnDefault:	/* add a pre-cooked default */
+			/* This is currently used only in CREATE TABLE */
+			/* (so the permission check really isn't necessary) */
+			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
+			/* This command never recurses */
+			pass = AT_PASS_ADD_OTHERCONSTR;
+			break;
 		case AT_AddIdentity:
 			ATSimplePermissions(rel, ATT_TABLE | ATT_VIEW | ATT_FOREIGN_TABLE);
 			/* This command never recurses */
@@ -4398,6 +4450,9 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 		case AT_ColumnDefault:	/* ALTER COLUMN DEFAULT */
 			address = ATExecColumnDefault(rel, cmd->name, cmd->def, lockmode);
 			break;
+		case AT_CookedColumnDefault:	/* add a pre-cooked default */
+			address = ATExecCookedColumnDefault(rel, cmd->num, cmd->def);
+			break;
 		case AT_AddIdentity:
 			cmd = ATParseTransformCmd(wqueue, tab, rel, cmd, false, lockmode,
 									  cur_pass, context);
@@ -6857,6 +6912,35 @@ ATExecColumnDefault(Relation rel, const char *colName,
 	return address;
 }
 
+/*
+ * Add a pre-cooked default expression.
+ *
+ * Return the address of the affected column.
+ */
+static ObjectAddress
+ATExecCookedColumnDefault(Relation rel, AttrNumber attnum,
+						  Node *newDefault)
+{
+	ObjectAddress address;
+
+	/* We assume no checking is required */
+
+	/*
+	 * Remove any old default for the column.  We use RESTRICT here for
+	 * safety, but at present we do not expect anything to depend on the
+	 * default.  (In ordinary cases, there could not be a default in place
+	 * anyway, but it's possible when combining LIKE with inheritance.)
+	 */
+	RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, false,
+					  true);
+
+	(void) StoreAttrDefault(rel, attnum, newDefault, true, false);
+
+	ObjectAddressSubSet(address, RelationRelationId,
+						RelationGetRelid(rel), attnum);
+	return address;
+}
+
 /*
  * ALTER TABLE ALTER COLUMN ADD IDENTITY
  *