Fix truncate of global temp tables

Author: knizhnik

src/backend/commands/sequence.c

@@ -1188,8 +1188,9 @@ read_seq_tuple(Relation rel, Buffer *buf, HeapTuple seqdatatuple)
 		/* Initialize sequence for global temporary tables */
 		Datum		value[SEQ_COL_LASTCOL] = {0};
 		bool		null[SEQ_COL_LASTCOL] = {false};
+		HeapTuple tuple;
 		value[SEQ_COL_LASTVAL-1] = Int64GetDatumFast(1); /* start sequence with 1 */
-		HeapTuple tuple = heap_form_tuple(RelationGetDescr(rel), value, null);
+		tuple = heap_form_tuple(RelationGetDescr(rel), value, null);
 		fill_seq_with_data(rel, tuple, *buf);
 	}
 

src/backend/commands/tablecmds.c

@@ -1773,7 +1773,8 @@ ExecuteTruncateGuts(List *explicit_rels, List *relids, List *relids_logged,
 		 * table or the current physical file to be thrown away anyway.
 		 */
 		if (rel->rd_createSubid == mySubid ||
-			rel->rd_newRelfilenodeSubid == mySubid)
+			rel->rd_newRelfilenodeSubid == mySubid ||
+			rel->rd_rel->relpersistence == RELPERSISTENCE_SESSION)
 		{
 			/* Immediate, non-rollbackable truncation is OK */
 			heap_truncate_one_rel(rel);

src/backend/storage/smgr/md.c

@@ -176,9 +176,6 @@ TruncateSessionRelations(int code, Datum arg)
 	SessionRelation* rel;
 	for (rel = SessionRelations; rel != NULL; rel = rel->next)
 	{
-		/* Remove relation pages from shared buffers */
-		DropRelFileNodesAllBuffers(&rel->rnode, 1);
-
 		/* Delete relation files */
 		mdunlink(rel->rnode, InvalidForkNumber, false);
 	}

src/include/storage/bufmgr.h

@@ -205,7 +205,7 @@ extern XLogRecPtr BufferGetLSNAtomic(Buffer buffer);
 extern void PrintPinnedBufs(void);
 #endif
 extern Size BufferShmemSize(void);
-extern void BufferGetTag(Buffer buffer, RelFileNodeBackend *rnode,
+extern void BufferGetTag(Buffer buffer, RelFileNode *rnode,
 						 ForkNumber *forknum, BlockNumber *blknum);
 
 extern void MarkBufferDirtyHint(Buffer buffer, bool buffer_std);