On 06/17/2014 12:14 PM, Ivan Shapovalov wrote:
On Tuesday 17 June 2014 at 02:37:16, Edward Shishkin wrote:
[...]
Yup, blocknr sets minimize memory consumption and are unsortable...
I think that the cleanest option will be using lists (instead of blocknr
sets) for
the delete sets, if the discard is turned on. It will reduce memory
consumption
by 20%. Indeed, every entry in a blocknr_set occupies ~8 bytes (assuming
that everything is pretty fragmented because of txmod=wa), whereas a list
entry occupies 32 bytes (start, length, plus 2 pointers for the link).
In this option we'll need to join lists (instead of merging blocknr
sets) during
atoms fusion and apply the list (instead of blocknr set) to the COMMIT
BITMAP
at pre_commit_hook(). I think it won't be a problem, since the lists are
simpler
than blocknr sets.
That's a neat approach. I think I'll use unions and do the decision at runtime.
Yup.
So, if discard is on, we work with 2 lists (delete_set,
delete_set_for_wander).
If discard is off, we work with one blocknr set..
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