Ensure that expandTableLikeClause() re-examines the same table.

tglsfdc · tglsfdc · commit f00c4400270f · 2020-12-01T14:02:28.000-05:00
As it stood, expandTableLikeClause() re-did the same relation_openrv call that transformTableLikeClause() had done. However there are scenarios where this would not find the same table as expected. We hold lock on the LIKE source table, so it can't be renamed or dropped, but another table could appear before it in the search path. This explains the odd behavior reported in bug #16758 when cloning a table as a temp table of the same name. This case worked as expected before commit 5028981 introduced the need to open the source table twice, so we should fix it. To make really sure we get the same table, let's re-open it by OID not name. That requires adding an OID field to struct TableLikeClause, which is a little nervous-making from an ABI standpoint, but as long as it's at the end I don't think there's any serious risk. Per bug #16758 from Marc Boeren. Like the previous patch, back-patch to all supported branches. Discussion: https://postgr.es/m/16758-840e84a6cfab276d@postgresql.org
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
@@ -3025,6 +3025,7 @@ _copyTableLikeClause(const TableLikeClause *from)
 
 	COPY_NODE_FIELD(relation);
 	COPY_SCALAR_FIELD(options);
+	COPY_SCALAR_FIELD(relationOid);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
@@ -1172,6 +1172,7 @@ _equalTableLikeClause(const TableLikeClause *a, const TableLikeClause *b)
 {
 	COMPARE_NODE_FIELD(relation);
 	COMPARE_SCALAR_FIELD(options);
+	COMPARE_SCALAR_FIELD(relationOid);
 
 	return true;
 }
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
@@ -2541,6 +2541,7 @@ _outTableLikeClause(StringInfo str, const TableLikeClause *node)
 
 	WRITE_NODE_FIELD(relation);
 	WRITE_UINT_FIELD(options);
+	WRITE_OID_FIELD(relationOid);
 }
 
 static void
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
@@ -3174,6 +3174,7 @@ TableLikeClause:
 					TableLikeClause *n = makeNode(TableLikeClause);
 					n->relation = $2;
 					n->options = $3;
+					n->relationOid = InvalidOid;
 					$$ = (Node *)n;
 				}
 		;
diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
@@ -909,12 +909,16 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla
 	 * yet know what column numbers the copied columns will have in the
 	 * finished table.  If any of those options are specified, add the LIKE
 	 * clause to cxt->likeclauses so that expandTableLikeClause will be called
-	 * after we do know that.
+	 * after we do know that.  Also, remember the relation OID so that
+	 * expandTableLikeClause is certain to open the same table.
 	 */
 	if (table_like_clause->options &
 		(CREATE_TABLE_LIKE_CONSTRAINTS |
 		 CREATE_TABLE_LIKE_INDEXES))
+	{
+		table_like_clause->relationOid = RelationGetRelid(relation);
 		cxt->likeclauses = lappend(cxt->likeclauses, table_like_clause);
+	}
 
 	/*
 	 * Close the parent rel, but keep our AccessShareLock on it until xact
@@ -948,9 +952,13 @@ expandTableLikeClause(RangeVar *heapRel, TableLikeClause *table_like_clause)
 	 * Open the relation referenced by the LIKE clause.  We should still have
 	 * the table lock obtained by transformTableLikeClause (and this'll throw
 	 * an assertion failure if not).  Hence, no need to recheck privileges
-	 * etc.
+	 * etc.  We must open the rel by OID not name, to be sure we get the same
+	 * table.
 	 */
-	relation = relation_openrv(table_like_clause->relation, NoLock);
+	if (!OidIsValid(table_like_clause->relationOid))
+		elog(ERROR, "expandTableLikeClause called on untransformed LIKE clause");
+
+	relation = relation_open(table_like_clause->relationOid, NoLock);
 
 	tupleDesc = RelationGetDescr(relation);
 	constr = tupleDesc->constr;
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
@@ -610,6 +610,7 @@ typedef struct TableLikeClause
 	NodeTag		type;
 	RangeVar   *relation;
 	bits32		options;		/* OR of TableLikeOption flags */
+	Oid			relationOid;	/* If table has been looked up, its OID */
 } TableLikeClause;
 
 typedef enum TableLikeOption
diff --git a/src/test/regress/expected/create_table_like.out b/src/test/regress/expected/create_table_like.out
@@ -275,6 +275,25 @@ Check constraints:
     "ctlt1_a_check" CHECK (length(a) > 2)
 
 DROP TABLE public.pg_attrdef;
+-- Check that LIKE isn't confused when new table masks the old, either
+BEGIN;
+CREATE SCHEMA ctl_schema;
+SET LOCAL search_path = ctl_schema, public;
+CREATE TABLE ctlt1 (LIKE ctlt1 INCLUDING ALL);
+\d+ ctlt1
+                     Table "ctl_schema.ctlt1"
+ Column | Type | Modifiers | Storage  | Stats target | Description 
+--------+------+-----------+----------+--------------+-------------
+ a      | text | not null  | main     |              | A
+ b      | text |           | extended |              | B
+Indexes:
+    "ctlt1_pkey" PRIMARY KEY, btree (a)
+    "ctlt1_b_idx" btree (b)
+    "ctlt1_expr_idx" btree ((a || b))
+Check constraints:
+    "ctlt1_a_check" CHECK (length(a) > 2)
+
+ROLLBACK;
 DROP TABLE ctlt1, ctlt2, ctlt3, ctlt4, ctlt12_storage, ctlt12_comments, ctlt1_inh, ctlt13_inh, ctlt13_like, ctlt_all, ctla, ctlb CASCADE;
 NOTICE:  drop cascades to table inhe
 /* LIKE with other relation kinds */
diff --git a/src/test/regress/sql/create_table_like.sql b/src/test/regress/sql/create_table_like.sql
@@ -122,6 +122,14 @@ CREATE TABLE pg_attrdef (LIKE ctlt1 INCLUDING ALL);
 \d+ public.pg_attrdef
 DROP TABLE public.pg_attrdef;
 
+-- Check that LIKE isn't confused when new table masks the old, either
+BEGIN;
+CREATE SCHEMA ctl_schema;
+SET LOCAL search_path = ctl_schema, public;
+CREATE TABLE ctlt1 (LIKE ctlt1 INCLUDING ALL);
+\d+ ctlt1
+ROLLBACK;
+
 DROP TABLE ctlt1, ctlt2, ctlt3, ctlt4, ctlt12_storage, ctlt12_comments, ctlt1_inh, ctlt13_inh, ctlt13_like, ctlt_all, ctla, ctlb CASCADE;
 
 

Original file line number	Diff line number	Diff line change
`@@ -3025,6 +3025,7 @@ _copyTableLikeClause(const TableLikeClause *from)`
`3025`	`3025`
`3026`	`3026`	`COPY_NODE_FIELD(relation);`
`3027`	`3027`	`COPY_SCALAR_FIELD(options);`
	`3028`	`+ COPY_SCALAR_FIELD(relationOid);`
`3028`	`3029`
`3029`	`3030`	`return newnode;`
`3030`	`3031`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1172,6 +1172,7 @@ _equalTableLikeClause(const TableLikeClause a, const TableLikeClause b)`
`1172`	`1172`	`{`
`1173`	`1173`	`COMPARE_NODE_FIELD(relation);`
`1174`	`1174`	`COMPARE_SCALAR_FIELD(options);`
	`1175`	`+ COMPARE_SCALAR_FIELD(relationOid);`
`1175`	`1176`
`1176`	`1177`	`return true;`
`1177`	`1178`	`}`
Original file line number	Diff line number	Diff line change
`@@ -2541,6 +2541,7 @@ _outTableLikeClause(StringInfo str, const TableLikeClause *node)`
`2541`	`2541`
`2542`	`2542`	`WRITE_NODE_FIELD(relation);`
`2543`	`2543`	`WRITE_UINT_FIELD(options);`
	`2544`	`+ WRITE_OID_FIELD(relationOid);`
`2544`	`2545`	`}`
`2545`	`2546`
`2546`	`2547`	`static void`
Original file line number	Diff line number	Diff line change
`@@ -3174,6 +3174,7 @@ TableLikeClause:`
`3174`	`3174`	`TableLikeClause *n = makeNode(TableLikeClause);`
`3175`	`3175`	`n->relation = $2;`
`3176`	`3176`	`n->options = $3;`
	`3177`	`+ n->relationOid = InvalidOid;`
`3177`	`3178`	`$$ = (Node *)n;`
`3178`	`3179`	`}`
`3179`	`3180`	`;`