Fix checkpoint after fast promotion.

The intention was to request a regular online checkpoint immediately after
end of recovery, when performing "fast promotion". However, because the
checkpoint was requested before other backends were allowed to write WAL,
the checkpointer process performed a restartpoint rather than a checkpoint.

Delay the RequestCheckPoint call until after recovery has truly ended, so
that you get a real checkpoint.

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 3155238c58de5a12d252db9d0bc42f3f7747ae86..140f9109a6f92e39658d76c8f35a0e32ee269de3 100644 (file)
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -4731,6 +4731,7 @@ StartupXLOG(void)
    DBState     dbstate_at_startup;
    XLogReaderState *xlogreader;
    XLogPageReadPrivate private;
+   bool        fast_promoted = false;
 
    /*
     * Read control file and check XLOG status looks valid.
@@ -5781,15 +5782,13 @@ StartupXLOG(void)
         * assigning a new TLI, using a shutdown checkpoint allows us to have
         * the rule that TLI only changes in shutdown checkpoints, which
         * allows some extra error checking in xlog_redo.
+        *
+        * In fast promotion, only create a lightweight end-of-recovery record
+        * instead of a full checkpoint. A checkpoint is requested later, after
+        * we're fully out of recovery mode and already accepting queries.
         */
        if (bgwriterLaunched)
        {
-           bool    checkpoint_wait = true;
-
-           /*
-            * If we've been explicitly promoted with fast option,
-            * end of recovery without a checkpoint if possible.
-            */
            if (fast_promote)
            {
                checkPointLoc = ControlFile->prevCheckPoint;
@@ -5802,22 +5801,15 @@ StartupXLOG(void)
                record = ReadCheckpointRecord(xlogreader, checkPointLoc, 1, false);
                if (record != NULL)
                {
-                   checkpoint_wait = false;
+                   fast_promoted = true;
                    CreateEndOfRecoveryRecord();
                }
            }
 
-           /*
-            * In most cases we will wait for a full checkpoint to complete.
-            *
-            * If not, issue a normal, non-immediate checkpoint but don't wait.
-            */
-           if (checkpoint_wait)
+           if (!fast_promoted)
                RequestCheckpoint(CHECKPOINT_END_OF_RECOVERY |
                                    CHECKPOINT_IMMEDIATE |
                                    CHECKPOINT_WAIT);
-           else
-               RequestCheckpoint(0);   /* No flags */
        }
        else
            CreateCheckPoint(CHECKPOINT_END_OF_RECOVERY | CHECKPOINT_IMMEDIATE);
@@ -5925,6 +5917,15 @@ StartupXLOG(void)
     * wal sender processes to notice that we've been promoted.
     */
    WalSndWakeup();
+
+   /*
+    * If this was a fast promotion, request an (online) checkpoint now. This
+    * isn't required for consistency, but the last restartpoint might be far
+    * back, and in case of a crash, recovering from it might take a longer
+    * than is appropriate now that we're not in standby mode anymore.
+    */
+   if (fast_promoted)
+       RequestCheckpoint(0);
 }
 
 /*