[tarantool-patches] Re: [PATCH 1/2] space: add method to fetch next rowid

Konstantin Osipov kostja at tarantool.org
Wed Nov 21 21:58:42 MSK 2018

* n.pettik <korablev at tarantool.org> [18/11/12 16:12]:
> It is true that 2^64 is likely to be quite huge number of tuples,
> but for instance JOIN uses nested-loop algorithm, so it requires
> n^2 memory for ephemeral table to comprise results.
> In this regard, to reach the limit we need 4-way join where each
> table contains 2^16 entries, which in turn doesn’t seem to be giant.
> *It is only thoughts tho, I haven’t tested it since I suppose very likely
>  my pc would simply get stuck.*

intel 64 bit architecture can not address more than 48 bits.

Apart from the fact that you can multiply 4 numbers in a cross
join there is a question how much time this nested loop is going
to run. Imagine it runs 2^48 processor ticks. It's several weeks
by a conservative estimate.
> I wanted to create long test as the easiest solution, but Alexander warned
> me that Travis may not survive such test due to lack of memory.

Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov

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