Hi!
On Oct 21, Mads Kristensen wrote:
> *snip*
> > Yes.
> > B-tree is always balanced: http://www.nist.gov/dads/HTML/btree.html
> >
> > Regards,
> > Sergei
> *snip*
>
> You are right, B+Trees are always balanced but.... When you insert in
> increasing order all your inserts will be to the last leaf of the
> B+tree. This means that you can get some concurrency problems when
> updating the index since it is always the same part of the index that
> needs to be locked.
>
> I'm not quite sure how MySQL does it locking, but if it locks only the
> index leafs that it is updating this kind of insertion will give poor
> performance compared to random insertion.
MyISAM uses table-level locks, so it always lock the complete index for
writes.
On the other hand, always writting to the last leaf, you constantly
touch only few nodes - on the path from the root to the last leaf. Thus
these nodes/keypages will be always cached and the performance should be
somewhat better as compared to random accesses (assuming the index is
too big to fit in cache completely).
Regards,
Sergei
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/ |/ /_ __/ __/ __ \/ / Sergei Golubchik <[EMAIL PROTECTED]>
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