1 files changed, 42 insertions, 0 deletions
diff --git a/src/include/access/xlogutils.h b/src/include/access/xlogutils.h
index 9ac602b674d..a5cb3d322c5 100644
--- a/src/include/access/xlogutils.h
+++ b/src/include/access/xlogutils.h
@@ -14,6 +14,48 @@
 #include "access/xlogreader.h"
 #include "storage/bufmgr.h"
 
+/*
+ * Prior to 8.4, all activity during recovery was carried out by the startup
+ * process. This local variable continues to be used in many parts of the
+ * code to indicate actions taken by RecoveryManagers. Other processes that
+ * potentially perform work during recovery should check RecoveryInProgress().
+ * See XLogCtl notes in xlog.c.
+ */
+extern bool InRecovery;
+
+/*
+ * Like InRecovery, standbyState is only valid in the startup process.
+ * In all other processes it will have the value STANDBY_DISABLED (so
+ * InHotStandby will read as false).
+ *
+ * In DISABLED state, we're performing crash recovery or hot standby was
+ * disabled in postgresql.conf.
+ *
+ * In INITIALIZED state, we've run InitRecoveryTransactionEnvironment, but
+ * we haven't yet processed a RUNNING_XACTS or shutdown-checkpoint WAL record
+ * to initialize our primary-transaction tracking system.
+ *
+ * When the transaction tracking is initialized, we enter the SNAPSHOT_PENDING
+ * state. The tracked information might still be incomplete, so we can't allow
+ * connections yet, but redo functions must update the in-memory state when
+ * appropriate.
+ *
+ * In SNAPSHOT_READY mode, we have full knowledge of transactions that are
+ * (or were) running on the primary at the current WAL location. Snapshots
+ * can be taken, and read-only queries can be run.
+ */
+typedef enum
+{
+	STANDBY_DISABLED,
+	STANDBY_INITIALIZED,
+	STANDBY_SNAPSHOT_PENDING,
+	STANDBY_SNAPSHOT_READY
+} HotStandbyState;
+
+extern HotStandbyState standbyState;
+
+#define InHotStandby (standbyState >= STANDBY_SNAPSHOT_PENDING)
+
 
 extern bool XLogHaveInvalidPages(void);
 extern void XLogCheckInvalidPages(void);