2 files changed, 104 insertions, 0 deletions

diff --git a/src/backend/backup/walsummaryfuncs.c b/src/backend/backup/walsummaryfuncs.c
index 89c660c6969..f082488b33f 100644
--- a/src/backend/backup/walsummaryfuncs.c
+++ b/src/backend/backup/walsummaryfuncs.c
@@ -16,11 +16,13 @@
 #include "common/blkreftable.h"
 #include "funcapi.h"
 #include "miscadmin.h"
+#include "postmaster/walsummarizer.h"
 #include "utils/fmgrprotos.h"
 #include "utils/pg_lsn.h"
 
 #define NUM_WS_ATTS			3
 #define NUM_SUMMARY_ATTS	6
+#define NUM_STATE_ATTS		4
 #define MAX_BLOCKS_PER_CALL	256
 
 /*
@@ -167,3 +169,40 @@ pg_wal_summary_contents(PG_FUNCTION_ARGS)
 
 	return (Datum) 0;
 }
+
+/*
+ * Returns information about the state of the WAL summarizer process.
+ */
+Datum
+pg_get_wal_summarizer_state(PG_FUNCTION_ARGS)
+{
+	Datum		values[NUM_STATE_ATTS];
+	bool		nulls[NUM_STATE_ATTS];
+	TimeLineID	summarized_tli;
+	XLogRecPtr	summarized_lsn;
+	XLogRecPtr	pending_lsn;
+	int			summarizer_pid;
+	TupleDesc	tupdesc;
+	HeapTuple	htup;
+
+	GetWalSummarizerState(&summarized_tli, &summarized_lsn, &pending_lsn,
+						  &summarizer_pid);
+
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	memset(nulls, 0, sizeof(nulls));
+
+	values[0] = Int64GetDatum((int64) summarized_tli);
+	values[1] = LSNGetDatum(summarized_lsn);
+	values[2] = LSNGetDatum(pending_lsn);
+
+	if (summarizer_pid < 0)
+		nulls[3] = true;
+	else
+		values[3] = Int32GetDatum(summarizer_pid);
+
+	htup = heap_form_tuple(tupdesc, values, nulls);
+
+	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+}
diff --git a/src/backend/postmaster/walsummarizer.c b/src/backend/postmaster/walsummarizer.c
index f828cc436a6..7287f07529e 100644
--- a/src/backend/postmaster/walsummarizer.c
+++ b/src/backend/postmaster/walsummarizer.c
@@ -142,6 +142,7 @@ static XLogRecPtr redo_pointer_at_last_summary_removal = InvalidXLogRecPtr;
 bool		summarize_wal = false;
 int			wal_summary_keep_time = 10 * 24 * 60;
 
+static void WalSummarizerShutdown(int code, Datum arg);
 static XLogRecPtr GetLatestLSN(TimeLineID *tli);
 static void HandleWalSummarizerInterrupts(void);
 static XLogRecPtr SummarizeWAL(TimeLineID tli, XLogRecPtr start_lsn,
@@ -245,6 +246,7 @@ WalSummarizerMain(void)
 	pqsignal(SIGUSR2, SIG_IGN); /* not used */
 
 	/* Advertise ourselves. */
+	on_shmem_exit(WalSummarizerShutdown, (Datum) 0);
 	LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE);
 	WalSummarizerCtl->summarizer_pgprocno = MyProc->pgprocno;
 	LWLockRelease(WALSummarizerLock);
@@ -418,6 +420,57 @@ WalSummarizerMain(void)
 }
 
 /*
+ * Get information about the state of the WAL summarizer.
+ */
+void
+GetWalSummarizerState(TimeLineID *summarized_tli, XLogRecPtr *summarized_lsn,
+					  XLogRecPtr *pending_lsn, int *summarizer_pid)
+{
+	LWLockAcquire(WALSummarizerLock, LW_SHARED);
+	if (!WalSummarizerCtl->initialized)
+	{
+		/*
+		 * If initialized is false, the rest of the structure contents are
+		 * undefined.
+		 */
+		*summarized_tli = 0;
+		*summarized_lsn = InvalidXLogRecPtr;
+		*pending_lsn = InvalidXLogRecPtr;
+		*summarizer_pid = -1;
+	}
+	else
+	{
+		int	summarizer_pgprocno = WalSummarizerCtl->summarizer_pgprocno;
+
+		*summarized_tli = WalSummarizerCtl->summarized_tli;
+		*summarized_lsn = WalSummarizerCtl->summarized_lsn;
+		if (summarizer_pgprocno == INVALID_PGPROCNO)
+		{
+			/*
+			 * If the summarizer has exited, the fact that it had processed
+			 * beyond summarized_lsn is irrelevant now.
+			 */
+			*pending_lsn = WalSummarizerCtl->summarized_lsn;
+			*summarizer_pid = -1;
+		}
+		else
+		{
+			*pending_lsn = WalSummarizerCtl->pending_lsn;
+
+			/*
+			 * We're not fussed about inexact answers here, since they could
+			 * become stale instantly, so we don't bother taking the lock, but
+			 * make sure that invalid PID values are normalized to -1.
+			 */
+			*summarizer_pid = GetPGProcByNumber(summarizer_pgprocno)->pid;
+			if (*summarizer_pid <= 0)
+				*summarizer_pid = -1;
+		}
+	}
+	LWLockRelease(WALSummarizerLock);
+}
+
+/*
  * Get the oldest LSN in this server's timeline history that has not yet been
  * summarized.
  *
@@ -623,6 +676,18 @@ WaitForWalSummarization(XLogRecPtr lsn, long timeout, XLogRecPtr *pending_lsn)
 }
 
 /*
+ * On exit, update shared memory to make it clear that we're no longer
+ * running.
+ */
+static void
+WalSummarizerShutdown(int code, Datum arg)
+{
+	LWLockAcquire(WALSummarizerLock, LW_EXCLUSIVE);
+	WalSummarizerCtl->summarizer_pgprocno = INVALID_PGPROCNO;
+	LWLockRelease(WALSummarizerLock);
+}
+
+/*
  * Get the latest LSN that is eligible to be summarized, and set *tli to the
  * corresponding timeline.
  */