Various utils for WAL

Author: vadim4o

src/backend/access/transam/xlogutils.c

@@ -0,0 +1,120 @@
+/*-------------------------------------------------------------------------
+ *
+ * xlog.c
+ *
+ *
+ * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xlog.h"
+#include "access/xact.h"
+
+#ifdef XLOG
+
+/*
+ * Check if specified heap tuple was inserted by given
+ * xaction/command and return
+ *
+ * - -1 if not
+ * - 0  if there is no tuple at all
+ * - 1  if yes
+ */
+int
+XLogIsOwnerOfTuple(RelFileNode hnode, ItemPointer iptr, 
+					TransactionId xid, CommandId cid)
+{
+	Relation		reln;
+	Buffer			buffer;
+	Page			page;
+	ItemId			lp;
+	HeapTupleHeader	htup;
+
+	reln = XLogOpenRelation(false, RM_HEAP_ID, hnode);
+	if (!RelationIsValid(reln))
+		return(0);
+
+	buffer = ReadBuffer(reln, ItemPointerGetBlockNumber(iptr));
+	if (!BufferIsValid(buffer))
+		return(0);
+
+	LockBuffer(buffer, BUFFER_LOCK_SHARE);
+	page = (Page) BufferGetPage(buffer);
+	if (PageIsNew((PageHeader) page) ||
+		ItemPointerGetOffsetNumber(iptr) > PageGetMaxOffsetNumber(page))
+	{
+		UnlockAndReleaseBuffer(buffer);
+		return(0);
+	}
+	lp = PageGetItemId(page, ItemPointerGetOffsetNumber(iptr));
+	if (!ItemIdIsUsed(lp) || ItemIdDeleted(lp))
+	{
+		UnlockAndReleaseBuffer(buffer);
+		return(0);
+	}
+
+	htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+	if (PageGetSUI(page) != ThisStartUpID || htup->t_xmin != xid || htup->t_cmin != cid)
+	{
+		UnlockAndReleaseBuffer(buffer);
+		return(-1);
+	}
+
+	UnlockAndReleaseBuffer(buffer);
+	return(1);
+}
+
+/*
+ * Check if exists valid (inserted by not aborted xaction) heap tuple
+ * for given item pointer
+ */
+bool
+XLogIsValidTuple(RelFileNode hnode, ItemPointer iptr)
+{
+	Relation		reln;
+	Buffer			buffer;
+	Page			page;
+	ItemId			lp;
+	HeapTupleHeader	htup;
+
+	reln = XLogOpenRelation(false, RM_HEAP_ID, hnode);
+	if (!RelationIsValid(reln))
+		return(false);
+
+	buffer = ReadBuffer(reln, ItemPointerGetBlockNumber(iptr));
+	if (!BufferIsValid(buffer))
+		return(false);
+
+	LockBuffer(buffer, BUFFER_LOCK_SHARE);
+	page = (Page) BufferGetPage(buffer);
+	if (PageIsNew((PageHeader) page) ||
+		ItemPointerGetOffsetNumber(iptr) > PageGetMaxOffsetNumber(page))
+	{
+		UnlockAndReleaseBuffer(buffer);
+		return(false);
+	}
+	lp = PageGetItemId(page, ItemPointerGetOffsetNumber(iptr));
+	if (!ItemIdIsUsed(lp) || ItemIdDeleted(lp))
+	{
+		UnlockAndReleaseBuffer(buffer);
+		return(false);
+	}
+
+	htup = (HeapTupleHeader) PageGetItem(page, lp);
+
+	if (XLogIsAborted(PageGetSUI(page), htup->t_xmin))
+	{
+		UnlockAndReleaseBuffer(buffer);
+		return(false);
+	}
+
+	UnlockAndReleaseBuffer(buffer);
+	return(true);
+}
+
+#endif