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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 / 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 .
| Is This Answer Correct ? | 4 Yes | 0 No |
Answer / saravanan
If COLLECT STATS has been defined on the table EMP, then PE
will avoid going for a FULL TABLE SCAN.
If not, PE will undergo a FULL TABLE SCAN to fetch
DEPTID=100
| Is This Answer Correct ? | 4 Yes | 2 No |
Answer / siva reddy
in case we are using nusi in this swicthvation subtable is created same amps.it is one of the full table scan but not full table scan.it's scan only all amps sub table.if any one of the match it will disply.here no allgorithem can be performed.
| Is This Answer Correct ? | 1 Yes | 0 No |
Answer / saravanan
If your question is about how Parsing engine would fetch
DEPTID=10, it will undergo a FULL TABLE scan since Dept_Id
is a Non unique secondary index.
| Is This Answer Correct ? | 1 Yes | 6 No |
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