postgres.git / summary / log / commit / refs

commit    3881aedbcfb5e1e36e2860d081e045fb5283f8cc
Author:   Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date:     Thu Dec 20 19:30:59 2012 +0000

    Fix recycling of WAL segments after changing recovery target timeline.
    
    After the recovery target timeline is changed, we would still recycle and
    preallocate WAL segments on the old target timeline. Those WAL segments
    created for the old timeline are a waste of space, although otherwise
    harmless.
    
    The problem is that when installing a recycled WAL segment as a future one,
    ThisTimeLineID is used to construct the filename. ThisTimeLineID is
    initialized in the checkpointer process to the recovery target timeline at
    startup, but it was not updated when the startup process chooses a new
    target timeline (recovery_target_timeline='latest'). To fix, always update
    ThisTimeLineID before recycling WAL segments at a restartpoint.
    
    This still leaves a small window where we might install WAL segments under
    wrong timeline ID, if the target timeline is changed just as we're about to
    start recycling. Also, when we're not on the target timeline yet, but still
    replaying some older timeline, we'll install WAL segments to the newer
    timeline anyway and they will still go wasted. We'll just live with the
    waste in that situation.
    
    Commit to 9.2 and 9.1. Older versions didn't change recovery target timeline
    after startup, and for master, I'll commit a slightly different variant of
    this.


 src/backend/access/transam/xlog.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 1d1e47b588c..5df6063be99 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8415,6 +8415,13 @@ CreateRestartPoint(int flags)
 
 		KeepLogSeg(endptr, &_logId, &_logSeg);
 		PrevLogSeg(_logId, _logSeg);
+
+		/*
+		 * Update ThisTimeLineID to the recovery target timeline, so that
+		 * we install any recycled segments on the correct timeline.
+		 */
+		ThisTimeLineID = GetRecoveryTargetTLI();
+
 		RemoveOldXlogFiles(_logId, _logSeg, endptr);
 
 		/*


[parent: 8e1e8278c35b]