Hive actually does this optimization (it is called semi-join reduction) by 
generating bloom-filters on one side and passing it on to the other side.
This is not a rewrite but instead a physical implementation.

Vineet

On Aug 29, 2018, at 10:34 AM, Vladimir Sitnikov 
<[email protected]<mailto:[email protected]>> wrote:

Nested loops are never likely to happe

What's wrong with that?

Apparently Andrei asks for that, and "subquery precomputation" is quite
close to nested loops in my opinion.

Vladimir

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