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Interview questions on aggregator transformation in informatica - Part -3

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Under what conditions selecting Sorted Input in aggregator will still not boost session per-formance?
 
Answer:

Incremental Aggregation, session option is enabled.

The aggregate expression contains nested aggregate functions. When session property, Treat Source rows as is set to data driven.


Under what condition selecting Sorted Input in aggregator may fail the session?

Answer:

If the input data is not sorted correctly, the session will fail.

Also if the input data is properly sorted, the session may fail if the sort order by ports and the group by ports of the aggregator are not in the same order.





Suppose we do not group by on any ports of the aggregator what will be the output.

Answer:

If we do not use an input port in group-by neither in aggregate expression, the Integration Ser-vice will return only the last row value of the column for the input rows.

For example, if we have 100 rows coming from source then aggregator will output only the last record (100th record)


What is the expected value if the column in an aggregator transformation is neither a group by nor an aggregate expression?

Answer:

Integration Service produces one row for each group based on the group by ports. The columns which are neither part of the key nor aggregate expression will return the corresponding value of last record of the group received.

However, if we specify particularly the FIRST function, the Integration Service then returns the value of the specified first row of the group. So default is the LAST function.
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