Tune GetSnapshotData() during Hot Standby by avoiding loop

through normal backends. Makes code clearer also, since we
avoid various Assert()s. Performance of snapshots taken
during recovery no longer depends upon number of read-only
backends.

src/backend/access/transam/xlog.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.397 2010/04/16 08:58:16 heikki Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.398 2010/04/18 18:05:51 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -6454,6 +6454,12 @@ CheckRecoveryConsistency(void)
 	}
 }
 
+bool
+XLogConsistentState(void)
+{
+	return reachedMinRecoveryPoint;
+}
+
 /*
  * Is the system still in recovery?
  *