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);
 }
 
 /*