Include the backend ID in the relpath of temporary relations.

This allows us to reliably remove all leftover temporary relation
files on cluster startup without reference to system catalogs or WAL;
therefore, we no longer include temporary relations in XLOG_XACT_COMMIT
and XLOG_XACT_ABORT WAL records.

Since these changes require including a backend ID in each
SharedInvalSmgrMsg, the size of the SharedInvalidationMessage.id
field has been reduced from two bytes to one, and the maximum number
of connections has been reduced from INT_MAX / 4 to 2^23-1.  It would
be possible to remove these restrictions by increasing the size of
SharedInvalidationMessage by 4 bytes, but right now that doesn't seem
like a good trade-off.

Review by Jaime Casanova and Tom Lane.

1 files changed, 25 insertions, 6 deletions

diff --git a/src/include/storage/relfilenode.h b/src/include/storage/relfilenode.h
index b5e4e1134d..9bf170b2c8 100644
--- a/src/include/storage/relfilenode.h
+++ b/src/include/storage/relfilenode.h
@@ -7,13 +7,15 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/relfilenode.h,v 1.25 2010/02/07 20:48:13 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/relfilenode.h,v 1.26 2010/08/13 20:10:53 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef RELFILENODE_H
 #define RELFILENODE_H
 
+#include "storage/backendid.h"
+
 /*
  * The physical storage of a relation consists of one or more forks. The
  * main fork is always created, but in addition to that there can be
@@ -37,7 +39,8 @@ typedef enum ForkNumber
 
 /*
  * RelFileNode must provide all that we need to know to physically access
- * a relation. Note, however, that a "physical" relation is comprised of
+ * a relation, with the exception of the backend ID, which can be provided
+ * separately. Note, however, that a "physical" relation is comprised of
  * multiple files on the filesystem, as each fork is stored as a separate
  * file, and each fork can be divided into multiple segments. See md.c.
  *
@@ -74,14 +77,30 @@ typedef struct RelFileNode
 } RelFileNode;
 
 /*
- * Note: RelFileNodeEquals compares relNode first since that is most likely
- * to be different in two unequal RelFileNodes.  It is probably redundant
- * to compare spcNode if the other two fields are found equal, but do it
- * anyway to be sure.
+ * Augmenting a relfilenode with the backend ID provides all the information
+ * we need to locate the physical storage.
+ */
+typedef struct RelFileNodeBackend
+{
+	RelFileNode	node;
+	BackendId	backend;
+} RelFileNodeBackend;
+
+/*
+ * Note: RelFileNodeEquals and RelFileNodeBackendEquals compare relNode first
+ * since that is most likely to be different in two unequal RelFileNodes.  It
+ * is probably redundant to compare spcNode if the other fields are found equal,
+ * but do it anyway to be sure.
  */
 #define RelFileNodeEquals(node1, node2) \
 	((node1).relNode == (node2).relNode && \
 	 (node1).dbNode == (node2).dbNode && \
 	 (node1).spcNode == (node2).spcNode)
 
+#define RelFileNodeBackendEquals(node1, node2) \
+	((node1).node.relNode == (node2).node.relNode && \
+	 (node1).node.dbNode == (node2).node.dbNode && \
+	 (node1).backend == (node2).backend && \
+	 (node1).node.spcNode == (node2).node.spcNode)
+
 #endif   /* RELFILENODE_H */