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Message Posted: Mon, 02 Nov 2015 @ 20:42:30 GMT
| Subj: || || Re: Multiple single-column SI vs Single Multi-column SI |
| From: || || Anomy Anom |
<-- Anonymously Posted: Monday, November 02, 2015 17:32 -->
The USI row contains the actual column values as well as the RowHash of those values and the RowID of the base row. No, you won't know which
AMP to check, but it may be cheaper to scan the USI subtable on all AMPs than to scan the table.
For a NUSI, the index "rows" are not hashed, they are locally ordered and always scanned rather than being accessed directly. ORDER BY HASH
provides a pseudo-random order while ORDER BY VALUES may allow you to skip forward and/or terminate the scan early.