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Re: MDEV-7004 review


Hi Sergei,

On Fri, Nov 28, 2014 at 10:35:09AM +0100, Sergei Golubchik wrote:
> Hi, Sergey!
> On Nov 28, Sergey Vojtovich wrote:
> > Eh, that's what I was afraid of. Not seeing elements that were added at about
> > the same time should always be acceptable. Can't it miss elements that were
> > in the list before iteration started (because it has moved to a different
> > location)? The latter is unacceptable in many cases.
> No, in this hash implementation elements are never moved in the list.
> It's prety difficult to move elements lock-free, that's why it wasn't
> easy to create a good performing lock-free hash. And this one works
> around this problem by not moving elements at all.
That's good.

> > But let's see:
> > - print_cached_tables() - old debug stuff, remove it?
> > - I_S.OPEN_TABLES - seeing elements twice is not good, use PFS?
> Duplicates can be removed on the upper layer. Like, I_S data are
> inserted into a temp table anyway, so a UNIQUE key would solve the issue
> of duplicates. Or a Unique object.
Ok, it is acceptable.

This all makes your hash iterator good for MDL and table cache.