Re: [HACKERS] Restricting maximum keep segments by repslots - Mailing list pgsql-hackers

At Tue, 30 Jul 2019 21:30:45 +0900 (Tokyo Standard Time), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in
<20190730.213045.221405075.horikyota.ntt@gmail.com>
> I attach the revised patch. I'll repost the polished version
> sooner.

This is the revised patch.

- Status criteria has been changed.

  "streaming" : restart_lsn is within max_wal_size. (and kept)

  "keeping" : restart_lsn is behind max_wal_size but still kept
       by max_slot_wal_keep_size or wal_keep_segments.

  "losing" : The segment for restart_lsn is being lost or has
       been lost, but active walsender (or session) using the
       slot is still running. If the walsender caught up before
       stopped, the state will transfer to "keeping" or
       "streaming" again.

  "lost" : The segment for restart_lsn has been lost and the
       active session on the slot is gone. The standby cannot
       continue replication using this slot.

  null : restart_lsn is null (never activated).

- remain is null if restart_lsn is null (never activated) or
  wal_status is "losing" or "lost".

- catalogs.sgml is updated.

- Refactored GetLsnAvailability and GetOldestKeepSegment and
  pg_get_replication_slots.

- TAP test is fied. But test for "losing" state cannot be done
  since it needs interactive session. (I think using isolation
  tester is too much)..

reards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center
From a7f2efdcf64eae2cd4fd707981658f29090d36ee Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Thu, 21 Dec 2017 21:20:20 +0900
Subject: [PATCH 1/6] Add WAL relief vent for replication slots

Replication slot is useful to maintain replication connection in the
configurations where replication is so delayed that connection is
broken. On the other hand so many WAL files can fill up disk that the
master downs by a long delay. This feature, which is activated by a
GUC "max_slot_wal_keep_size", protects master servers from suffering
disk full by limiting the number of WAL files reserved by replication
slots.
---
 src/backend/access/transam/xlog.c             | 128 +++++++++++++++++++++-----
 src/backend/replication/slot.c                |  62 +++++++++++++
 src/backend/utils/misc/guc.c                  |  12 +++
 src/backend/utils/misc/postgresql.conf.sample |   1 +
 src/include/access/xlog.h                     |   1 +
 src/include/replication/slot.h                |   1 +
 6 files changed, 180 insertions(+), 25 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index f553523857..3989f6e54a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -104,6 +104,7 @@ int            wal_level = WAL_LEVEL_MINIMAL;
 int            CommitDelay = 0;    /* precommit delay in microseconds */
 int            CommitSiblings = 5; /* # concurrent xacts needed to sleep */
 int            wal_retrieve_retry_interval = 5000;
+int            max_slot_wal_keep_size_mb = -1;
 
 #ifdef WAL_DEBUG
 bool        XLOG_DEBUG = false;
@@ -872,6 +873,7 @@ static void checkTimeLineSwitch(XLogRecPtr lsn, TimeLineID newTLI,
 static void LocalSetXLogInsertAllowed(void);
 static void CreateEndOfRecoveryRecord(void);
 static void CheckPointGuts(XLogRecPtr checkPointRedo, int flags);
+static XLogSegNo GetOldestKeepSegment(XLogRecPtr currpos, XLogRecPtr minSlotPtr);
 static void KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo);
 static XLogRecPtr XLogGetReplicationSlotMinimumLSN(void);
 
@@ -9288,6 +9290,54 @@ CreateRestartPoint(int flags)
     return true;
 }
 
+/*
+ * Returns minimum segment number that the next checkpoint must leave
+ * considering wal_keep_segments, replication slots and
+ * max_slot_wal_keep_size.
+ *
+ * currLSN is the current insert location.
+ * minSlotLSN is the minimum restart_lsn of all active slots.
+ */
+static XLogSegNo
+GetOldestKeepSegment(XLogRecPtr currLSN, XLogRecPtr minSlotLSN)
+{
+    XLogSegNo    currSeg;
+    XLogSegNo    minSlotSeg;
+    uint64        keepSegs = 0;    /* # of segments actually kept */
+
+    XLByteToSeg(currLSN, currSeg, wal_segment_size);
+    XLByteToSeg(minSlotLSN, minSlotSeg, wal_segment_size);
+
+    /*
+     * Calculate how many segments are kept by slots first. The second
+     * term of the condition is just a sanity check.
+     */
+    if (minSlotLSN != InvalidXLogRecPtr && minSlotSeg <= currSeg)
+        keepSegs = currSeg - minSlotSeg;
+
+    /* Cap keepSegs by max_slot_wal_keep_size */
+    if (max_slot_wal_keep_size_mb >= 0)
+    {
+        uint64 limitSegs;
+
+        limitSegs = ConvertToXSegs(max_slot_wal_keep_size_mb, wal_segment_size);
+
+        /* Reduce it if slots already reserves too many. */
+        if (limitSegs < keepSegs)
+            keepSegs = limitSegs;
+    }
+
+    /* but, keep at least wal_keep_segments segments if any */
+    if (wal_keep_segments > 0 && keepSegs < wal_keep_segments)
+        keepSegs = wal_keep_segments;
+
+    /* avoid underflow, don't go below 1 */
+    if (currSeg <= keepSegs)
+        return 1;
+
+    return currSeg - keepSegs;
+}
+
 /*
  * Retreat *logSegNo to the last segment that we need to retain because of
  * either wal_keep_segments or replication slots.
@@ -9299,38 +9349,66 @@ CreateRestartPoint(int flags)
 static void
 KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo)
 {
-    XLogSegNo    segno;
-    XLogRecPtr    keep;
+    XLogRecPtr    slotminptr = InvalidXLogRecPtr;
+    XLogSegNo    minSegNo;
+    XLogSegNo    slotSegNo;
 
-    XLByteToSeg(recptr, segno, wal_segment_size);
-    keep = XLogGetReplicationSlotMinimumLSN();
+    if (max_replication_slots > 0)
+        slotminptr = XLogGetReplicationSlotMinimumLSN();
 
-    /* compute limit for wal_keep_segments first */
-    if (wal_keep_segments > 0)
+    /*
+     * We should keep certain number of WAL segments after this checkpoint.
+     */
+    minSegNo = GetOldestKeepSegment(recptr, slotminptr);
+
+    /*
+     * Warn the checkpoint is going to flush the segments required by
+     * replication slots.
+     */
+    if (!XLogRecPtrIsInvalid(slotminptr))
     {
-        /* avoid underflow, don't go below 1 */
-        if (segno <= wal_keep_segments)
-            segno = 1;
+        static XLogSegNo prev_lost_segs = 0;    /* avoid duplicate messages */
+
+        XLByteToSeg(slotminptr, slotSegNo, wal_segment_size);
+
+        if (slotSegNo < minSegNo)
+        {
+            XLogSegNo lost_segs = minSegNo - slotSegNo;
+            if (prev_lost_segs != lost_segs)
+            {
+                /* We have lost a new segment, warn it.*/
+                XLogRecPtr minlsn;
+                char *slot_names;
+                int nslots;
+
+                XLogSegNoOffsetToRecPtr(minSegNo, 0, wal_segment_size, minlsn);
+                slot_names =
+                    ReplicationSlotsEnumerateBehinds(minlsn, ", ", &nslots);
+
+                /*
+                 * Some of the affected slots could have just been removed. We
+                 * don't need show anything here if no affected slots are
+                 * remaining.
+                 */
+                if (slot_names)
+                {
+                    ereport(WARNING,
+                            (errmsg ("some replication slots have lost required WAL segments"),
+                             errdetail_plural(
+                                 "Slot %s lost %ld segment(s).",
+                                 "Slots %s lost at most %ld segment(s).",
+                                 nslots, slot_names, lost_segs)));
+                }
+            }
+            prev_lost_segs = lost_segs;
+        }
         else
-            segno = segno - wal_keep_segments;
-    }
-
-    /* then check whether slots limit removal further */
-    if (max_replication_slots > 0 && keep != InvalidXLogRecPtr)
-    {
-        XLogSegNo    slotSegNo;
-
-        XLByteToSeg(keep, slotSegNo, wal_segment_size);
-
-        if (slotSegNo <= 0)
-            segno = 1;
-        else if (slotSegNo < segno)
-            segno = slotSegNo;
+            prev_lost_segs = 0;
     }
 
     /* don't delete WAL segments newer than the calculated segment */
-    if (segno < *logSegNo)
-        *logSegNo = segno;
+    if (minSegNo < *logSegNo)
+        *logSegNo = minSegNo;
 }
 
 /*
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 62342a69cb..5bdf1e90fb 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1064,6 +1064,68 @@ ReplicationSlotReserveWal(void)
     }
 }
 
+/*
+ * Returns names of inactive replication slots that their restart_lsn are
+ * behind specified LSN for the purpose of error message, in palloc'ed
+ * character array stuffed with slot names delimited by the given
+ * separator. Returns NULL if no slot matches. If pnslots is given, the number
+ * of the returned slots is returned there.
+ */
+char *
+ReplicationSlotsEnumerateBehinds(XLogRecPtr target, char *separator, int *pnslots)
+{
+    static StringInfoData retstr;
+    static bool retstr_initialized = false;
+    bool insert_separator = false;
+    int i;
+    int nslots = 0;
+
+    Assert (separator);
+    if (max_replication_slots <= 0)
+        return NULL;
+
+    if (!retstr_initialized)
+    {
+        initStringInfo(&retstr);
+        retstr_initialized = true;
+    }
+    else
+        resetStringInfo(&retstr);
+
+    /* construct name list */
+    LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+    for (i = 0 ; i < max_replication_slots ; i++)
+    {
+        ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
+
+        /*
+         * We are collecting slots that are definitely behind the given target
+         * LSN. Active slots are exluded since they can catch up later.
+         */
+        if (s->in_use && s->active_pid == 0 && s->data.restart_lsn < target)
+        {
+            if (insert_separator)
+                appendStringInfoString(&retstr, separator);
+
+            /*
+             * Slot names consist only with lower-case letters. We don't
+             * bother quoting.
+             */
+            appendStringInfoString(&retstr, NameStr(s->data.name));
+            insert_separator = true;
+            nslots++;
+        }
+    }
+    LWLockRelease(ReplicationSlotControlLock);
+
+    /* return the number of slots in the list if requested */
+    if (pnslots)
+        *pnslots = nslots;
+
+    /* return NULL instead of an empty string */
+    return retstr.data[0] ? retstr.data : NULL;
+}
+
 /*
  * Flush all replication slots to disk.
  *
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index fc463601ff..f8e796b6c1 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2654,6 +2654,18 @@ static struct config_int ConfigureNamesInt[] =
         NULL, NULL, NULL
     },
 
+    {
+        {"max_slot_wal_keep_size", PGC_SIGHUP, REPLICATION_SENDING,
+            gettext_noop("Sets the maximum size of extra WALs kept by replication slots."),
+         NULL,
+         GUC_UNIT_MB
+        },
+        &max_slot_wal_keep_size_mb,
+        -1, -1,
+        MAX_KILOBYTES, /* XXX: This is in megabytes, like max/min_wal_size */
+        NULL, NULL, NULL
+    },
+
     {
         {"wal_sender_timeout", PGC_USERSET, REPLICATION_SENDING,
             gettext_noop("Sets the maximum time to wait for WAL replication."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index cfad86c02a..aadbc76d85 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -286,6 +286,7 @@
 #max_wal_senders = 10        # max number of walsender processes
                 # (change requires restart)
 #wal_keep_segments = 0        # in logfile segments; 0 disables
+#max_slot_wal_keep_size = -1    # measured in bytes; -1 disables
 #wal_sender_timeout = 60s    # in milliseconds; 0 disables
 
 #max_replication_slots = 10    # max number of replication slots
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index d519252aad..b355452072 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -108,6 +108,7 @@ extern int    wal_segment_size;
 extern int    min_wal_size_mb;
 extern int    max_wal_size_mb;
 extern int    wal_keep_segments;
+extern int    max_slot_wal_keep_size_mb;
 extern int    XLOGbuffers;
 extern int    XLogArchiveTimeout;
 extern int    wal_retrieve_retry_interval;
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 8fbddea78f..e0fee0663c 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -199,6 +199,7 @@ extern void ReplicationSlotsComputeRequiredLSN(void);
 extern XLogRecPtr ReplicationSlotsComputeLogicalRestartLSN(void);
 extern bool ReplicationSlotsCountDBSlots(Oid dboid, int *nslots, int *nactive);
 extern void ReplicationSlotsDropDBSlots(Oid dboid);
+extern char *ReplicationSlotsEnumerateBehinds(XLogRecPtr target, char *separator, int *pnslots);
 
 extern void StartupReplicationSlots(void);
 extern void CheckPointReplicationSlots(void);
-- 
2.16.3

From 68232445aca90c9d104c58893f45db6f740354b3 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Thu, 21 Dec 2017 21:23:25 +0900
Subject: [PATCH 2/6] Add monitoring aid for max_slot_wal_keep_size

Adds two columns "status" and "remain" in pg_replication_slot. Setting
max_slot_wal_keep_size, replication connections may lose sync by a
long delay. The "status" column shows whether the slot is
reconnectable or not, or about to lose reserving WAL segments. The
"remain" column shows the remaining bytes of WAL that can be advance
until the slot loses required WAL records.
---
 contrib/test_decoding/expected/ddl.out |   4 +-
 contrib/test_decoding/sql/ddl.sql      |   2 +
 src/backend/access/transam/xlog.c      | 157 +++++++++++++++++++++++++++++++--
 src/backend/catalog/system_views.sql   |   4 +-
 src/backend/replication/slotfuncs.c    |  17 +++-
 src/include/access/xlog.h              |   2 +
 src/include/catalog/pg_proc.dat        |   6 +-
 src/test/regress/expected/rules.out    |   6 +-
 8 files changed, 181 insertions(+), 17 deletions(-)

diff --git a/contrib/test_decoding/expected/ddl.out b/contrib/test_decoding/expected/ddl.out
index 2c999fd3eb..cf0318f697 100644
--- a/contrib/test_decoding/expected/ddl.out
+++ b/contrib/test_decoding/expected/ddl.out
@@ -723,8 +723,8 @@ SELECT pg_drop_replication_slot('regression_slot');
 (1 row)
 
 /* check that the slot is gone */
+\x
 SELECT * FROM pg_replication_slots;
- slot_name | plugin | slot_type | datoid | database | temporary | active | active_pid | xmin | catalog_xmin |
restart_lsn| confirmed_flush_lsn 
 

------------+--------+-----------+--------+----------+-----------+--------+------------+------+--------------+-------------+---------------------
 (0 rows)
 
+\x
diff --git a/contrib/test_decoding/sql/ddl.sql b/contrib/test_decoding/sql/ddl.sql
index 856495c952..0f2b9992f7 100644
--- a/contrib/test_decoding/sql/ddl.sql
+++ b/contrib/test_decoding/sql/ddl.sql
@@ -387,4 +387,6 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'inc
 SELECT pg_drop_replication_slot('regression_slot');
 
 /* check that the slot is gone */
+\x
 SELECT * FROM pg_replication_slots;
+\x
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 3989f6e54a..f4cab30d5d 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -873,7 +873,8 @@ static void checkTimeLineSwitch(XLogRecPtr lsn, TimeLineID newTLI,
 static void LocalSetXLogInsertAllowed(void);
 static void CreateEndOfRecoveryRecord(void);
 static void CheckPointGuts(XLogRecPtr checkPointRedo, int flags);
-static XLogSegNo GetOldestKeepSegment(XLogRecPtr currpos, XLogRecPtr minSlotPtr);
+static XLogSegNo GetOldestKeepSegment(XLogRecPtr currpos, XLogRecPtr minSlotPtr,
+                                      XLogRecPtr targetLSN, int64 *restBytes);
 static void KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo);
 static XLogRecPtr XLogGetReplicationSlotMinimumLSN(void);
 
@@ -9290,6 +9291,96 @@ CreateRestartPoint(int flags)
     return true;
 }
 
+/*
+ * Detect availability of the record at given targetLSN.
+ *
+ * targetLSN is restart_lsn of a slot.
+ * walsender_pid is the slot's walsender PID.
+ * restBytes is the pointer to uint64 variable, to store the remaining bytes
+ * until the slot goes into "losing" state.
+ *
+ * Returns in for kinds of strings.
+ *
+ * "streaming" means targetLSN is available because it is in the range of
+ * max_wal_size.
+ *
+ * "keeping" means it is still available by preserving extra segments beyond
+ * max_wal_size.
+ *
+ * "losing" means it is being removed or already removed but the walsender
+ * that using the given slot is keeping repliation stream yet. The state may
+ * return to "keeping" or "streaming" state if the walsender advances
+ * restart_lsn.
+ *
+ * "lost" means it is definitly lost. The walsender worked on the slot has
+ * been stopped.
+ *
+ * returns NULL if restart_lsn is invalid.
+ *
+ * -1 is stored to restBytes if the values is useless.
+ */
+char *
+GetLsnAvailability(XLogRecPtr restart_lsn, pid_t walsender_pid,
+                   int64 *restBytes)
+{
+    XLogRecPtr currpos;
+    XLogRecPtr slotPtr;
+    XLogSegNo currSeg;        /* segid of currpos */
+    XLogSegNo restartSeg;    /* segid of restart_lsn */
+    XLogSegNo oldestSeg;    /* oldest segid kept by max_wal_size */
+    XLogSegNo oldestSlotSeg;/* oldest segid kept by slot */
+
+    Assert(restBytes);
+
+    /* the case where the slot has never been activated */
+    if (XLogRecPtrIsInvalid(restart_lsn))
+    {
+        *restBytes = -1;
+        return NULL;
+    }
+
+    /*
+     * slot limitation is not activated, WAL files are kept unlimitedlllly in
+     * the case.
+     */
+    if (max_slot_wal_keep_size_mb < 0)
+    {
+        *restBytes = -1;
+        return "streaming";
+    }
+
+    currpos = GetXLogWriteRecPtr();
+
+    /* oldest segment currently needed by slots */
+    XLByteToSeg(restart_lsn, restartSeg, wal_segment_size);
+    slotPtr = XLogGetReplicationSlotMinimumLSN();
+    oldestSlotSeg = GetOldestKeepSegment(currpos, slotPtr, restart_lsn,
+                                         restBytes);
+
+    /* oldest segment by max_wal_size */
+    XLByteToSeg(currpos, currSeg, wal_segment_size);
+    oldestSeg = currSeg -
+        ConvertToXSegs(max_wal_size_mb, wal_segment_size) + 1;
+
+    /* restartSeg is within max_wal_size */
+    if (oldestSeg <= restartSeg)
+        return "streaming";
+
+    /* being retained by slots */
+    if (oldestSlotSeg <= restartSeg)
+        return "keeping";
+
+    /* it is useless for the states below */
+    *restBytes = -1;
+
+    /* no longer protected, but the working walsender can advance restart_lsn */
+    if (walsender_pid != 0)
+        return    "losing";
+
+    /* definitely lost. stopped walsender can no longer restart */
+    return "lost";
+}
+
 /*
  * Returns minimum segment number that the next checkpoint must leave
  * considering wal_keep_segments, replication slots and
@@ -9297,13 +9388,19 @@ CreateRestartPoint(int flags)
  *
  * currLSN is the current insert location.
  * minSlotLSN is the minimum restart_lsn of all active slots.
+ * targetLSN is used when restBytes is not NULL.
+ *
+ * If restBytes is not NULL, sets the remaining LSN bytes until the segment
+ * for targetLSN will be removed.
  */
 static XLogSegNo
-GetOldestKeepSegment(XLogRecPtr currLSN, XLogRecPtr minSlotLSN)
+GetOldestKeepSegment(XLogRecPtr currLSN, XLogRecPtr minSlotLSN,
+                     XLogRecPtr targetLSN, int64 *restBytes)
 {
     XLogSegNo    currSeg;
     XLogSegNo    minSlotSeg;
     uint64        keepSegs = 0;    /* # of segments actually kept */
+    uint64        limitSegs = 0;    /* # of maximum segments possibly kept */
 
     XLByteToSeg(currLSN, currSeg, wal_segment_size);
     XLByteToSeg(minSlotLSN, minSlotSeg, wal_segment_size);
@@ -9318,8 +9415,6 @@ GetOldestKeepSegment(XLogRecPtr currLSN, XLogRecPtr minSlotLSN)
     /* Cap keepSegs by max_slot_wal_keep_size */
     if (max_slot_wal_keep_size_mb >= 0)
     {
-        uint64 limitSegs;
-
         limitSegs = ConvertToXSegs(max_slot_wal_keep_size_mb, wal_segment_size);
 
         /* Reduce it if slots already reserves too many. */
@@ -9327,9 +9422,54 @@ GetOldestKeepSegment(XLogRecPtr currLSN, XLogRecPtr minSlotLSN)
             keepSegs = limitSegs;
     }
 
-    /* but, keep at least wal_keep_segments segments if any */
-    if (wal_keep_segments > 0 && keepSegs < wal_keep_segments)
-        keepSegs = wal_keep_segments;
+    if (wal_keep_segments > 0)
+    {
+        /* but, keep at least wal_keep_segments segments if any */
+        if (keepSegs < wal_keep_segments)
+            keepSegs = wal_keep_segments;
+
+        /* ditto for limitSegs */
+        if (limitSegs < wal_keep_segments)
+            limitSegs = wal_keep_segments;
+    }
+
+    /*
+     * If requested, calculate the remaining LSN bytes until the slot gives up
+     * keeping WAL records.
+     */
+    if (restBytes)
+    {
+        uint64 fragbytes;
+        XLogSegNo targetSeg;
+
+        *restBytes = 0;
+
+        XLByteToSeg(targetLSN, targetSeg, wal_segment_size);
+
+        /* avoid underflow */
+        if (currSeg <= targetSeg + limitSegs)
+        {
+            uint64 restbytes;
+
+            /*
+             * This slot still has all required segments. Calculate how
+             * many LSN bytes the slot has until it loses targetLSN.
+             */
+            fragbytes = wal_segment_size - (currLSN % wal_segment_size);
+            XLogSegNoOffsetToRecPtr(targetSeg + limitSegs - currSeg,
+                                    fragbytes, wal_segment_size,
+                                    restbytes);
+
+            /*
+             * not realistic, but make sure that it is not out of the
+             * range of int64. No problem to do so since such large values
+             * have no significant difference.
+             */
+            if (restbytes > PG_INT64_MAX)
+                restbytes = PG_INT64_MAX;
+            *restBytes = restbytes;
+        }
+    }
 
     /* avoid underflow, don't go below 1 */
     if (currSeg <= keepSegs)
@@ -9359,7 +9499,8 @@ KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo)
     /*
      * We should keep certain number of WAL segments after this checkpoint.
      */
-    minSegNo = GetOldestKeepSegment(recptr, slotminptr);
+    minSegNo = GetOldestKeepSegment(recptr, slotminptr, InvalidXLogRecPtr,
+                                    NULL);
 
     /*
      * Warn the checkpoint is going to flush the segments required by
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index ea4c85e395..6a9491e64a 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -849,7 +849,9 @@ CREATE VIEW pg_replication_slots AS
             L.xmin,
             L.catalog_xmin,
             L.restart_lsn,
-            L.confirmed_flush_lsn
+            L.confirmed_flush_lsn,
+            L.wal_status,
+            L.remain
     FROM pg_get_replication_slots() AS L
             LEFT JOIN pg_database D ON (L.datoid = D.oid);
 
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index 808a6f5b83..5c65c116d2 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -221,7 +221,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
 Datum
 pg_get_replication_slots(PG_FUNCTION_ARGS)
 {
-#define PG_GET_REPLICATION_SLOTS_COLS 11
+#define PG_GET_REPLICATION_SLOTS_COLS 13
     ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
     TupleDesc    tupdesc;
     Tuplestorestate *tupstore;
@@ -276,6 +276,8 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
         Oid            database;
         NameData    slot_name;
         NameData    plugin;
+        char       *walstate;
+        int64        remaining_bytes;
         int            i;
 
         if (!slot->in_use)
@@ -343,6 +345,19 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
         else
             nulls[i++] = true;
 
+        walstate =
+            GetLsnAvailability(restart_lsn, active_pid, &remaining_bytes);
+
+        if (walstate)
+            values[i++] = CStringGetTextDatum(walstate);
+        else
+            nulls[i++] = true;
+
+        if (remaining_bytes >= 0)
+            values[i++] = Int64GetDatum(remaining_bytes);
+        else
+            nulls[i++] = true;
+
         tuplestore_putvalues(tupstore, tupdesc, values, nulls);
     }
     LWLockRelease(ReplicationSlotControlLock);
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index b355452072..b021d12835 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -305,6 +305,8 @@ extern void ShutdownXLOG(int code, Datum arg);
 extern void InitXLOGAccess(void);
 extern void CreateCheckPoint(int flags);
 extern bool CreateRestartPoint(int flags);
+extern char *GetLsnAvailability(XLogRecPtr restart_lsn, pid_t walsender_pid,
+                                int64 *restBytes);
 extern void XLogPutNextOid(Oid nextOid);
 extern XLogRecPtr XLogRestorePoint(const char *rpName);
 extern void UpdateFullPageWrites(void);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 0902dce5f1..300d868980 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -9844,9 +9844,9 @@
   proname => 'pg_get_replication_slots', prorows => '10', proisstrict => 'f',
   proretset => 't', provolatile => 's', prorettype => 'record',
   proargtypes => '',
-  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames =>
'{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn}',
+  proallargtypes => '{name,name,text,oid,bool,bool,int4,xid,xid,pg_lsn,pg_lsn,text,int8}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames =>
'{slot_name,plugin,slot_type,datoid,temporary,active,active_pid,xmin,catalog_xmin,restart_lsn,confirmed_flush_lsn,wal_status,remain}',
   prosrc => 'pg_get_replication_slots' },
 { oid => '3786', descr => 'set up a logical replication slot',
   proname => 'pg_create_logical_replication_slot', provolatile => 'v',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 210e9cd146..74c44891a4 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1461,8 +1461,10 @@ pg_replication_slots| SELECT l.slot_name,
     l.xmin,
     l.catalog_xmin,
     l.restart_lsn,
-    l.confirmed_flush_lsn
-   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin,
catalog_xmin,restart_lsn, confirmed_flush_lsn)
 
+    l.confirmed_flush_lsn,
+    l.wal_status,
+    l.remain
+   FROM (pg_get_replication_slots() l(slot_name, plugin, slot_type, datoid, temporary, active, active_pid, xmin,
catalog_xmin,restart_lsn, confirmed_flush_lsn, wal_status, remain)
 
      LEFT JOIN pg_database d ON ((l.datoid = d.oid)));
 pg_roles| SELECT pg_authid.rolname,
     pg_authid.rolsuper,
-- 
2.16.3

From 306381b4ca2ec2335f73d7f7ebfc3c4a96d53dd9 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Wed, 19 Dec 2018 12:43:57 +0900
Subject: [PATCH 3/6] Add primary_slot_name to init_from_backup in TAP test.

It is convenient that priary_slot_name can be specified on taking a
base backup. This adds a new parameter of the name to the perl
function.
---
 src/test/perl/PostgresNode.pm | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/test/perl/PostgresNode.pm b/src/test/perl/PostgresNode.pm
index 6019f37f91..c7e138c121 100644
--- a/src/test/perl/PostgresNode.pm
+++ b/src/test/perl/PostgresNode.pm
@@ -694,6 +694,10 @@ port = $port
         $self->append_conf('postgresql.conf',
             "unix_socket_directories = '$host'");
     }
+    $self->append_conf('postgresql.conf',
+                       qq(primary_slot_name = $params{primary_slot_name}))
+      if (defined $params{primary_slot_name});
+
     $self->enable_streaming($root_node) if $params{has_streaming};
     $self->enable_restoring($root_node) if $params{has_restoring};
     return;
-- 
2.16.3

From 19c4243383229ccd200bf0ac30744a37b5b5695e Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Thu, 21 Dec 2017 17:33:53 +0900
Subject: [PATCH 4/6] TAP test for the slot limit feature

---
 src/test/recovery/t/018_replslot_limit.pl | 202 ++++++++++++++++++++++++++++++
 1 file changed, 202 insertions(+)
 create mode 100644 src/test/recovery/t/018_replslot_limit.pl

diff --git a/src/test/recovery/t/018_replslot_limit.pl b/src/test/recovery/t/018_replslot_limit.pl
new file mode 100644
index 0000000000..4b41a68faa
--- /dev/null
+++ b/src/test/recovery/t/018_replslot_limit.pl
@@ -0,0 +1,202 @@
+# Test for replication slot limit
+# Ensure that max_slot_wal_keep_size limits the number of WAL files to
+# be kept by replication slots.
+
+use strict;
+use warnings;
+use File::Path qw(rmtree);
+use PostgresNode;
+use TestLib;
+use Test::More tests => 13;
+use Time::HiRes qw(usleep);
+
+$ENV{PGDATABASE} = 'postgres';
+
+# Initialize master node, setting wal-segsize to 1MB
+my $node_master = get_new_node('master');
+$node_master->init(allows_streaming => 1, extra => ['--wal-segsize=1']);
+$node_master->append_conf('postgresql.conf', qq(
+min_wal_size = 2MB
+max_wal_size = 3MB
+log_checkpoints = yes
+));
+$node_master->start;
+$node_master->safe_psql('postgres', "SELECT pg_create_physical_replication_slot('rep1')");
+
+# The slot state and remain should be null before the first connection
+my $result = $node_master->safe_psql('postgres', "SELECT restart_lsn is NULL, wal_status is NULL, remain is NULL FROM
pg_replication_slotsWHERE slot_name = 'rep1'");
 
+is($result, "t|t|t", 'check the state of non-reserved slot is "unknown"');
+
+
+# Take backup
+my $backup_name = 'my_backup';
+$node_master->backup($backup_name);
+
+# Create a standby linking to it using the replication slot
+my $node_standby = get_new_node('standby_1');
+$node_standby->init_from_backup($node_master, $backup_name, has_streaming => 1, primary_slot_name => 'rep1');
+
+$node_standby->start;
+
+# Wait until standby has replayed enough data
+my $start_lsn = $node_master->lsn('write');
+$node_master->wait_for_catchup($node_standby, 'replay', $start_lsn);
+
+# Stop standby
+$node_standby->stop;
+
+
+# Preparation done, the slot is the state "streaming" now
+$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, remain is NULL FROM
pg_replication_slotsWHERE slot_name = 'rep1'");
 
+is($result, "$start_lsn|streaming|t", 'check the catching-up state');
+
+# Advance WAL by five segments (= 5MB) on master
+advance_wal($node_master, 1);
+$node_master->safe_psql('postgres', "CHECKPOINT;");
+
+# The slot is always "safe" when fitting max_wal_size
+$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, remain is NULL FROM
pg_replication_slotsWHERE slot_name = 'rep1'");
 
+is($result, "$start_lsn|streaming|t", 'check that restart_lsn is in max_wal_size');
+
+advance_wal($node_master, 4);
+$node_master->safe_psql('postgres', "CHECKPOINT;");
+
+# The slot is always "safe" when max_slot_wal_keep_size is not set
+$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, remain is NULL FROM
pg_replication_slotsWHERE slot_name = 'rep1'");
 
+is($result, "$start_lsn|streaming|t", 'check that slot is working');
+
+# The standby can reconnect to master
+$node_standby->start;
+
+$start_lsn = $node_master->lsn('write');
+$node_master->wait_for_catchup($node_standby, 'replay', $start_lsn);
+
+$node_standby->stop;
+
+# Set max_slot_wal_keep_size on master
+my $max_slot_wal_keep_size_mb = 4;
+$node_master->append_conf('postgresql.conf', qq(
+max_slot_wal_keep_size = ${max_slot_wal_keep_size_mb}MB
+));
+$node_master->reload;
+
+# The slot is in safe state. The remaining bytes should be as almost
+# (max_slot_wal_keep_size + 1) times large as the segment size
+$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, pg_size_pretty(remain) as remain FROM
pg_replication_slotsWHERE slot_name = 'rep1'");
 
+is($result, "$start_lsn|streaming|5120 kB", 'check that max_slot_wal_keep_size is working');
+
+# Advance WAL again then checkpoint, reducing remain by 2 MB.
+advance_wal($node_master, 2);
+$node_master->safe_psql('postgres', "CHECKPOINT;");
+
+# The slot is still working
+$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, pg_size_pretty(remain) as remain FROM
pg_replication_slotsWHERE slot_name = 'rep1'");
 
+is($result, "$start_lsn|streaming|3072 kB", 'check that remaining byte is calculated correctly');
+
+# wal_keep_segments overrides max_slot_wal_keep_size
+$result = $node_master->safe_psql('postgres', "ALTER SYSTEM SET wal_keep_segments to 6; SELECT pg_reload_conf();");
+$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, pg_size_pretty(remain) as remain FROM
pg_replication_slotsWHERE slot_name = 'rep1'");
 
+is($result, "$start_lsn|streaming|5120 kB", 'check that wal_keep_segments overrides max_slot_wal_keep_size');
+
+# restore wal_keep_segments
+$result = $node_master->safe_psql('postgres', "ALTER SYSTEM SET wal_keep_segments to 0; SELECT pg_reload_conf();");
+
+# Advance WAL again without checkpoint, reducing remain by 2 MB.
+advance_wal($node_master, 2);
+
+# Slot gets into 'keeping' state
+$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, pg_size_pretty(remain) as remain FROM
pg_replication_slotsWHERE slot_name = 'rep1'");
 
+is($result, "$start_lsn|keeping|1024 kB", 'check that the slot state changes to "keeping"');
+
+# do checkpoint so that the next checkpoint runs too early
+$node_master->safe_psql('postgres', "CHECKPOINT;");
+
+# Advance WAL again without checkpoint; remain goes to 0.
+advance_wal($node_master, 1);
+
+# Slot gets into 'lost' state
+$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, remain is NULL FROM
pg_replication_slotsWHERE slot_name = 'rep1'");
 
+is($result, "$start_lsn|lost|t", 'check that the slot state changes to "lost"');
+
+# The standby still can connect to master before a checkpoint
+$node_standby->start;
+
+$start_lsn = $node_master->lsn('write');
+$node_master->wait_for_catchup($node_standby, 'replay', $start_lsn);
+
+$node_standby->stop;
+
+ok(!find_in_log($node_standby,
+                "requested WAL segment [0-9A-F]+ has already been removed"),
+   'check that required WAL segments are still available');
+
+# Advance WAL again, the slot loses the oldest segment.
+my $logstart = get_log_size($node_master);
+advance_wal($node_master, 5);
+$node_master->safe_psql('postgres', "CHECKPOINT;");
+
+# WARNING should be issued
+ok(find_in_log($node_master,
+               "some replication slots have lost required WAL segments\n".
+               ".*Slot rep1 lost 1 segment\\(s\\)\\.",
+               $logstart),
+   'check that the warning is logged');
+
+# This slot should be broken
+$result = $node_master->safe_psql('postgres', "SELECT restart_lsn, wal_status, remain is NULL FROM
pg_replication_slotsWHERE slot_name = 'rep1'");
 
+is($result, "$start_lsn|lost|t", 'check that the slot state changes to "lost"');
+
+# The standby no longer can connect to the master
+$logstart = get_log_size($node_standby);
+$node_standby->start;
+
+my $failed = 0;
+for (my $i = 0 ; $i < 10000 ; $i++)
+{
+    if (find_in_log($node_standby,
+                    "requested WAL segment [0-9A-F]+ has already been removed",
+                    $logstart))
+    {
+        $failed = 1;
+        last;
+    }
+    usleep(100_000);
+}
+ok($failed, 'check that replication has been broken');
+
+$node_standby->stop;
+
+#####################################
+# Advance WAL of $node by $n segments
+sub advance_wal
+{
+    my ($node, $n) = @_;
+
+    # Advance by $n segments (= (16 * $n) MB) on master
+    for (my $i = 0 ; $i < $n ; $i++)
+    {
+        $node->safe_psql('postgres', "CREATE TABLE t (); DROP TABLE t; SELECT pg_switch_wal();");
+    }
+}
+
+# return the size of logfile of $node in bytes
+sub get_log_size
+{
+    my ($node) = @_;
+
+    return (stat $node->logfile)[7];
+}
+
+# find $pat in logfile of $node after $off-th byte
+sub find_in_log
+{
+    my ($node, $pat, $off) = @_;
+
+    $off = 0 unless defined $off;
+    my $log = TestLib::slurp_file($node->logfile);
+    return 0 if (length($log) <= $off);
+
+    $log = substr($log, $off);
+
+    return $log =~ m/$pat/;
+}
-- 
2.16.3

From 531d600ebe100b53568f4b1ddf2defb2722abbd4 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Thu, 11 Jan 2018 15:00:32 +0900
Subject: [PATCH 5/6] Documentation for slot-limit feature

---
 doc/src/sgml/catalogs.sgml          | 37 +++++++++++++++++++++++++++++++++++++
 doc/src/sgml/config.sgml            | 23 +++++++++++++++++++++++
 doc/src/sgml/high-availability.sgml |  8 +++++---
 3 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 68ad5071ca..3605e34149 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -9975,6 +9975,43 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
       </entry>
      </row>
 
+     <row>
+      <entry><structfield>wal_status</structfield></entry>
+      <entry><type>text</type></entry>
+      <entry></entry>
+
+      <entry>Availability of WAL records claimed by this
+      slot. <literal>streaming</literal>, <literal>keeping</literal>,
+      <literal>losing</literal> or <literal>lost</literal>.
+      <literal>streaming</literal> means that the claimed records are
+      available within max_wal_size. <literal>keeping</literal> means
+      max_wal_size is exceeded but still held by replication slots or
+      wal_keep_segments.
+      <literal>losing</literal> means that some of them are on the verge of
+      removal but the using session may go furether.
+      <literal>lost</literal> means that some of them are definitely lost and
+      the session that used this slot cannot continue replication. This state
+      also implies the using session has been stopped.
+
+      The last two states are seen only when
+      <xref linkend="guc-max-slot-wal-keep-size"/> is
+      non-negative. If <structfield>restart_lsn</structfield> is NULL, this
+      field is null.
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>remain</structfield></entry>
+      <entry><type>bigint</type></entry>
+      <entry></entry>
+      <entry>The amount in bytes WAL location (LSN) can advance that bytes
+        until this slot may lose required WAL
+        records. If <structfield>restart_lsn</structfield> is null
+        or <structfield>wal_status</structfield> is <literal>losing</literal>
+        or <literal>lost</literal>, this field is null.
+      </entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index c91e3e1550..c345538c8f 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3650,6 +3650,29 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
       </listitem>
      </varlistentry>
 
+      <varlistentry id="guc-max-slot-wal-keep-size" xreflabel="max_slot_wal_keep_size">
+       <term><varname>max_slot_wal_keep_size</varname> (<type>integer</type>)
+       <indexterm>
+        <primary><varname>max_slot_wal_keep_size</varname> configuration parameter</primary>
+       </indexterm>
+       </term>
+       <listitem>
+       <para>
+        Specify the maximum size of WAL files
+        that <link linkend="streaming-replication-slots">replication
+        slots</link> are allowed to retain in the <filename>pg_wal</filename>
+        directory at checkpoint time.
+        If <varname>max_slot_wal_keep_size</varname> is -1 (the default),
+        replication slots retain unlimited amount of WAL files.  If
+        restart_lsn of a replication slot gets behind more than that megabytes
+        from the current LSN, the standby using the slot may no longer be able
+        to continue replication due to removal of required WAL records. You
+        can see the WAL availability of replication slots
+        in <link linkend="view-pg-replication-slots">pg_replication_slots</link>.
+       </para>
+       </listitem>
+      </varlistentry>
+
      <varlistentry id="guc-wal-sender-timeout" xreflabel="wal_sender_timeout">
       <term><varname>wal_sender_timeout</varname> (<type>integer</type>)
       <indexterm>
diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index 543691dad4..ae8c3a2aca 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -925,9 +925,11 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass'
     <xref linkend="guc-archive-command"/>.
     However, these methods often result in retaining more WAL segments than
     required, whereas replication slots retain only the number of segments
-    known to be needed.  An advantage of these methods is that they bound
-    the space requirement for <literal>pg_wal</literal>; there is currently no way
-    to do this using replication slots.
+    known to be needed.  On the other hand, replication slots can retain so
+    many WAL segments that they fill up the space allocated
+    for <literal>pg_wal</literal>;
+    <xref linkend="guc-max-slot-wal-keep-size"/> limits the size of WAL files
+    retained by replication slots.
    </para>
    <para>
     Similarly, <xref linkend="guc-hot-standby-feedback"/>
-- 
2.16.3

From b5d6d702e0d36fde05323b647baa7b36e86f273b Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Fri, 26 Oct 2018 10:07:05 +0900
Subject: [PATCH 6/6] Check removal of in-reading segment file.

Checkpoints can recycle a segment file while it is being read by
ReadRecord and that leads to an apparently odd error message during
logical decoding. This patch explicitly checks that then error out
immediately.  Reading a recycled file is safe. Inconsistency caused by
overwrites as a new segment are caught by page/record validation. So
this is only for keeping consistency with the wal_status shown in
pg_replication_slots.
---
 src/backend/access/transam/xlogreader.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 33ccfc1553..4999892932 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -27,6 +27,7 @@
 
 #ifndef FRONTEND
 #include "miscadmin.h"
+#include "access/xlog.h"
 #include "utils/memutils.h"
 #endif
 
@@ -225,7 +226,9 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
     uint32        pageHeaderSize;
     bool        gotheader;
     int            readOff;
-
+#ifndef FRONTEND
+    XLogSegNo    targetSegNo;
+#endif
     /*
      * randAccess indicates whether to verify the previous-record pointer of
      * the record we're reading.  We only do this if we're reading
@@ -271,6 +274,22 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
     targetPagePtr = RecPtr - (RecPtr % XLOG_BLCKSZ);
     targetRecOff = RecPtr % XLOG_BLCKSZ;
 
+#ifndef FRONTEND
+    /*
+     * Although It's safe that the current segment is recycled as a new
+     * segment since we check the page/record header at reading, it leads to
+     * an apparently strange error message when logical replication, which can
+     * be prevented by explicitly checking if the current segment is removed.
+     */
+    XLByteToSeg(targetPagePtr, targetSegNo, state->wal_segment_size);
+    if (targetSegNo <= XLogGetLastRemovedSegno())
+    {
+        report_invalid_record(state,
+                              "WAL segment for LSN %X/%X has been removed",
+                              (uint32)(RecPtr >> 32), (uint32) RecPtr);
+        goto err;
+    }
+#endif
     /*
      * Read the page containing the record into state->readBuf. Request enough
      * byte to cover the whole record header, or at least the part of it that
-- 
2.16.3