Combine cmin and cmax fields of HeapTupleHeaders into a single field, by

keeping private state in each backend that has inserted and deleted the same
tuple during its current top-level transaction.  This is sufficient since
there is no need to be able to determine the cmin/cmax from any other
transaction.  This gets us back down to 23-byte headers, removing a penalty
paid in 8.0 to support subtransactions.  Patch by Heikki Linnakangas, with
minor revisions by moi, following a design hashed out awhile back on the
pghackers list.

1 files changed, 25 insertions, 0 deletions

diff --git a/src/include/utils/combocid.h b/src/include/utils/combocid.h
new file mode 100644
index 00000000000..b9497a68a53
--- /dev/null
+++ b/src/include/utils/combocid.h
@@ -0,0 +1,25 @@
+/*-------------------------------------------------------------------------
+ *
+ * combocid.h
+ *	  Combo command ID support routines
+ *
+ *
+ * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * $PostgreSQL: pgsql/src/include/utils/combocid.h,v 1.1 2007/02/09 03:35:34 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef COMBOCID_H
+#define COMBOCID_H
+
+/*
+ * HeapTupleHeaderGetCmin and HeapTupleHeaderGetCmax function prototypes
+ * are in access/htup.h, because that's where the macro definitions that
+ * those functions replaced used to be.
+ */
+
+extern void AtEOXact_ComboCid(void);
+
+#endif   /* COMBOCID_H */