At Fri, 02 Oct 2020 11:44:46 +0900 (JST), Kyotaro Horiguchi <horikyota....@gmail.com> wrote in > At Thu, 1 Oct 2020 12:55:34 +0000, "k.jami...@fujitsu.com" > <k.jami...@fujitsu.com> wrote in > - * XXX currently it sequentially searches the buffer pool, should > be > - * changed to more clever ways of searching. However, this routine > - * is used only in code paths that aren't very > performance-critical, > - * and we shouldn't slow down the hot paths to make it faster ... > + * XXX The relation might have extended before this, so this path > is > + * only optimized during recovery when we can get a reliable cached > + * value of blocks for specified relation. In addition, it is > safe to > + * do this since there are no other processes but the startup > process > + * that changes the relation size during recovery. Otherwise, or > if > + * not in recovery, proceed to usual invalidation process, where it > + * sequentially searches the buffer pool. > > This should no longer be a XXX comment. It seems to me somewhat > describing too-detailed at this function's level. How about something > like the follwoing? (excpet its syntax, or phrasing:p) > > === > If the expected maximum number of buffers to drop is small enough > compared to NBuffers, individual buffers are located by > BufTableLookup. Otherwise we scan through all buffers. Snnce we > mustn't leave a buffer behind, we take the latter way unless the > number is not reliably identified. See smgrcachednblocks() for > details. > ===
The second to last phrase is inversed, and some typos are found. FWIW this is the revised version. ==== If we are expected to drop buffers less enough, we locate individual buffers using BufTableLookup. Otherwise we scan through all buffers. Since we mustn't leave a buffer behind, we take the latter way unless the sizes of all the involved forks are known to be accurte. See smgrcachednblocks() for details. ==== regards. -- Kyotaro Horiguchi NTT Open Source Software Center
