1. 08 Nov, 2011 7 commits
  2. 07 Nov, 2011 4 commits
  3. 06 Nov, 2011 2 commits
  4. 05 Nov, 2011 4 commits
    • Magnus Hagander's avatar
      Update regression tests for \d+ modification · 3a6e4076
      Magnus Hagander authored
      Noted by Tom
      3a6e4076
    • Magnus Hagander's avatar
      ebcadba2
    • Magnus Hagander's avatar
    • Tom Lane's avatar
      Don't assume that a tuple's header size is unchanged during toasting. · 039680af
      Tom Lane authored
      This assumption can be wrong when the toaster is passed a raw on-disk
      tuple, because the tuple might pre-date an ALTER TABLE ADD COLUMN operation
      that added columns without rewriting the table.  In such a case the tuple's
      natts value is smaller than what we expect from the tuple descriptor, and
      so its t_hoff value could be smaller too.  In fact, the tuple might not
      have a null bitmap at all, and yet our current opinion of it is that it
      contains some trailing nulls.
      
      In such a situation, toast_insert_or_update did the wrong thing, because
      to save a few lines of code it would use the old t_hoff value as the offset
      where heap_fill_tuple should start filling data.  This did not leave enough
      room for the new nulls bitmap, with the result that the first few bytes of
      data could be overwritten with null flag bits, as in a recent report from
      Hubert Depesz Lubaczewski.
      
      The particular case reported requires ALTER TABLE ADD COLUMN followed by
      CREATE TABLE AS SELECT * FROM ... or INSERT ... SELECT * FROM ..., and
      further requires that there be some out-of-line toasted fields in one of
      the tuples to be copied; else we'll not reach the troublesome code.
      The problem can only manifest in this form in 8.4 and later, because
      before commit a77eaa6a, CREATE TABLE AS or
      INSERT/SELECT wouldn't result in raw disk tuples getting passed directly
      to heap_insert --- there would always have been at least a junkfilter in
      between, and that would reconstitute the tuple header with an up-to-date
      t_natts and hence t_hoff.  But I'm backpatching the tuptoaster change all
      the way anyway, because I'm not convinced there are no older code paths
      that present a similar risk.
      039680af
  5. 04 Nov, 2011 7 commits
  6. 03 Nov, 2011 12 commits
  7. 02 Nov, 2011 4 commits
    • Tom Lane's avatar
      Avoid scanning nulls at the beginning of a btree index scan. · 1a77f8b6
      Tom Lane authored
      If we have an inequality key that constrains the other end of the index,
      it doesn't directly help us in doing the initial positioning ... but it
      does imply a NOT NULL constraint on the index column.  If the index stores
      nulls at this end, we can use the implied NOT NULL condition for initial
      positioning, just as if it had been stated explicitly.  This avoids wasting
      time when there are a lot of nulls in the column.  This is the reverse of
      the examples given in bugs #6278 and #6283, which were about failing to
      stop early when we encounter nulls at the end of the indexscan.
      1a77f8b6
    • Tom Lane's avatar
      Fix btree stop-at-nulls logic properly. · 882368e8
      Tom Lane authored
      As pointed out by Naoya Anzai, my previous try at this was a few bricks
      shy of a load, because I had forgotten that the initial-positioning logic
      might not try to skip over nulls at the end of the index the scan will
      start from.  We ought to fix that, because it represents an unnecessary
      inefficiency, but first let's get the scan-stop logic back to a safe
      state.  With this patch, we preserve the performance benefit requested
      in bug #6278 for the case of scanning forward into NULLs (in a NULLS
      LAST index), but the reverse case of scanning backward across NULLs
      when there's no suitable initial-positioning qual is still inefficient.
      882368e8
    • Simon Riggs's avatar
    • Simon Riggs's avatar
      Reduce checkpoints and WAL traffic on low activity database server · 18fb9d8d
      Simon Riggs authored
      Previously, we skipped a checkpoint if no WAL had been written since
      last checkpoint, though this does not appear in user documentation.
      As of now, we skip a checkpoint until we have written at least one
      enough WAL to switch the next WAL file. This greatly reduces the
      level of activity and number of WAL messages generated by a very
      low activity server. This is safe because the purpose of a checkpoint
      is to act as a starting place for a recovery, in case of crash.
      This patch maintains minimal WAL volume for replay in case of crash,
      thus maintaining very low crash recovery time.
      18fb9d8d