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Message Posted: Fri, 02 Nov 2012 @ 20:47:48 GMT

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There is no problem with the hashing, it is to do with the access - single/two amp access for a USI or an ALL amp operation for a NUSI.

When accessing a NUSI an ALL amp operation is initiated to access the index subtable rows in each of the amp. From the index subtable, the base row ids pointing to the base table rows within the same AMP are accessed(thereby avoiding relocating of the base table rows in another AMP). Thus making the NUSI subtable as AMP local.

This is different when we access a USI, wherein it is a single/two amp operation. First the respective amp for a given index value is accessed and then the index subtable is probed to get the base table row which 'may' reside on the same amp(single AMP operation) or may reside on another amp(two amp).

Narayan
Wipro

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