On Wed, Sep 2, 2009 at 8:45 PM, Tom Lane<t...@sss.pgh.pa.us> wrote: > Greg Stark <gsst...@mit.edu> writes: >> The backwards scan is awful for rotating media. The reading from the >> end and writing to the beginning is bad too, though hopefully the >> cache can help that. > > Yeah. And all that pales in comparison to what happens in the indexes. > You have to insert index entries (retail) for each moved-in tuple,
Hm, that could be addressed by buffering index inserts in backend local memory. That's something Heikki proposed a long time ago primarily for improving bulk data loading. Basically it would be a retail version of the bulk loader that we saw at the 10th anniversary where you merge a sorted list into the index. You would still have to flush the buffer at transaction commit but even if it only buffered a few dozen tuples if they're in the same region of the index it would be a win. In this case it could probably buffer hundreds and merge them all into the index en masse. -- greg http://mit.edu/~gsstark/resume.pdf -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
