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I have a table with emp id, emp name, dept id and sal where
dept id is NUSI. SEL * FROM EMP WHERE DEPTID = 100. Can any
one explain how it will fetch the record.
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Answer Posted / ajain
Whenever NUSI is created, subtable will be created for each AMP's with the fields rowid and secondary index value.For NUSI ,subtable will be AMP local ie it will be having the records which are specific to the particular AMP.
When someone queries with the NUSI, all the AMPs will search in their own subtable for particular secondary index .For AMPs which found the particular record in their subtable ,it will retrieve the actual data from the AMP and PE will be consolidating the records and give to user
Since NUSI involves all AMP operation , PE will be deciding whether FULL table scan or ALL AMP operation will be more efficient .
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