Avoid index rebuild for no-rewrite ALTER TABLE .. ALTER TYPE.

Noah Misch.  Review and minor cosmetic changes by me.

Author: robertmhaas

doc/src/sgml/xindex.sgml

@@ -834,8 +834,10 @@ ALTER OPERATOR FAMILY integer_ops USING btree ADD
   <para>
    In a B-tree operator family, all the operators in the family must sort
    compatibly, meaning that the transitive laws hold across all the data types
-   supported by the family: <quote>if A = B and B = C, then A =
-   C</>, and <quote>if A &lt; B and B &lt; C, then A &lt; C</>.  For each
+   supported by the family: <quote>if A = B and B = C, then A = C</>,
+   and <quote>if A &lt; B and B &lt; C, then A &lt; C</>.  Moreover, implicit
+   or binary coercion casts between types represented in the operator family
+   must not change the associated sort ordering.  For each
    operator in the family there must be a support function having the same
    two input data types as the operator.  It is recommended that a family be
    complete, i.e., for each combination of data types, all operators are
@@ -851,6 +853,9 @@ ALTER OPERATOR FAMILY integer_ops USING btree ADD
    by the family's equality operators, even when the values are of different
    types.  This is usually difficult to accomplish when the types have
    different physical representations, but it can be done in some cases.
+   Furthermore, casting a value from one data type represented in the operator
+   family to another data type also represented in the operator family via
+   an implicit or binary coercion cast must not change the computed hash value.
    Notice that there is only one support function per data type, not one
    per equality operator.  It is recommended that a family be complete, i.e.,
    provide an equality operator for each combination of data types.

src/backend/bootstrap/bootparse.y

@@ -217,6 +217,7 @@ Boot_CreateStmt:
 												   PG_CATALOG_NAMESPACE,
 												   shared_relation ? GLOBALTABLESPACE_OID : 0,
 												   $3,
+												   InvalidOid,
 												   tupdesc,
 												   RELKIND_RELATION,
 												   RELPERSISTENCE_PERMANENT,
@@ -284,6 +285,7 @@ Boot_DeclareIndexStmt:
 					DefineIndex(makeRangeVar(NULL, $6, -1),
 								$3,
 								$4,
+								InvalidOid,
 								$8,
 								NULL,
 								$10,
@@ -302,6 +304,7 @@ Boot_DeclareUniqueIndexStmt:
 					DefineIndex(makeRangeVar(NULL, $7, -1),
 								$4,
 								$5,
+								InvalidOid,
 								$9,
 								NULL,
 								$11,

src/backend/catalog/heap.c

@@ -229,7 +229,8 @@ SystemAttributeByName(const char *attname, bool relhasoids)
  *		heap_create		- Create an uncataloged heap relation
  *
  *		Note API change: the caller must now always provide the OID
- *		to use for the relation.
+ *		to use for the relation.  The relfilenode may (and, normally,
+ *		should) be left unspecified.
  *
  *		rel->rd_rel is initialized by RelationBuildLocalRelation,
  *		and is mostly zeroes at return.
@@ -240,6 +241,7 @@ heap_create(const char *relname,
 			Oid relnamespace,
 			Oid reltablespace,
 			Oid relid,
+			Oid relfilenode,
 			TupleDesc tupDesc,
 			char relkind,
 			char relpersistence,
@@ -296,6 +298,16 @@ heap_create(const char *relname,
 			break;
 	}
 
+	/*
+	 * Unless otherwise requested, the physical ID (relfilenode) is initially
+	 * the same as the logical ID (OID).  When the caller did specify a
+	 * relfilenode, it already exists; do not attempt to create it.
+	 */
+	if (OidIsValid(relfilenode))
+		create_storage = false;
+	else
+		relfilenode = relid;
+
 	/*
 	 * Never allow a pg_class entry to explicitly specify the database's
 	 * default tablespace in reltablespace; force it to zero instead. This
@@ -315,6 +327,7 @@ heap_create(const char *relname,
 									 relnamespace,
 									 tupDesc,
 									 relid,
+									 relfilenode,
 									 reltablespace,
 									 shared_relation,
 									 mapped_relation,
@@ -1103,6 +1116,7 @@ heap_create_with_catalog(const char *relname,
 							   relnamespace,
 							   reltablespace,
 							   relid,
+							   InvalidOid,
 							   tupdesc,
 							   relkind,
 							   relpersistence,

src/backend/catalog/index.c

@@ -649,6 +649,8 @@ UpdateIndexRelation(Oid indexoid,
  * indexRelationId: normally, pass InvalidOid to let this routine
  *		generate an OID for the index.	During bootstrap this may be
  *		nonzero to specify a preselected OID.
+ * relFileNode: normally, pass InvalidOid to get new storage.  May be
+ *		nonzero to attach an existing valid build.
  * indexInfo: same info executor uses to insert into the index
  * indexColNames: column names to use for index (List of char *)
  * accessMethodObjectId: OID of index AM to use
@@ -674,6 +676,7 @@ Oid
 index_create(Relation heapRelation,
 			 const char *indexRelationName,
 			 Oid indexRelationId,
+			 Oid relFileNode,
 			 IndexInfo *indexInfo,
 			 List *indexColNames,
 			 Oid accessMethodObjectId,
@@ -813,6 +816,7 @@ index_create(Relation heapRelation,
 								namespaceId,
 								tableSpaceId,
 								indexRelationId,
+								relFileNode,
 								indexTupDesc,
 								RELKIND_INDEX,
 								relpersistence,

src/backend/catalog/storage.c

@@ -206,10 +206,13 @@ RelationDropStorage(Relation rel)
  * The relation mapper fixes this by telling us to not delete such relations
  * after all as part of its commit.
  *
+ * We also use this to reuse an old build of an index during ALTER TABLE, this
+ * time removing the delete-at-commit entry.
+ *
  * No-op if the relation is not among those scheduled for deletion.
  */
 void
-RelationPreserveStorage(RelFileNode rnode)
+RelationPreserveStorage(RelFileNode rnode, bool atCommit)
 {
 	PendingRelDelete *pending;
 	PendingRelDelete *prev;
@@ -219,11 +222,9 @@ RelationPreserveStorage(RelFileNode rnode)
 	for (pending = pendingDeletes; pending != NULL; pending = next)
 	{
 		next = pending->next;
-		if (RelFileNodeEquals(rnode, pending->relnode))
+		if (RelFileNodeEquals(rnode, pending->relnode)
+			&& pending->atCommit == atCommit)
 		{
-			/* we should only find delete-on-abort entries, else trouble */
-			if (pending->atCommit)
-				elog(ERROR, "cannot preserve a delete-on-commit relation");
 			/* unlink and delete list entry */
 			if (prev)
 				prev->next = next;

src/backend/catalog/toasting.c

@@ -274,7 +274,7 @@ create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid, Datum reloptio
 	coloptions[0] = 0;
 	coloptions[1] = 0;
 
-	index_create(toast_rel, toast_idxname, toastIndexOid,
+	index_create(toast_rel, toast_idxname, toastIndexOid, InvalidOid,
 				 indexInfo,
 				 list_make2("chunk_id", "chunk_seq"),
 				 BTREE_AM_OID,