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FAQ: What Join algorithms are used by the PowerCenter Joiner transformation?
Answer
When using a Joiner transformation, the session log shows messages referring to Join algorithm Nested Loop and Sorted Merge.

Example

TT_11098 INFO: Joiner [JNR_A] is set up with join algorithm: Sorted-Merge.
TT_11098 INFO: Joiner [JNR_B] is set up with join algorithm: Nested-Loop.

These messages refer to the algorithm used to perform the joining of two sources.

Sorted Merge is the more efficient algorithm. Nested Loop requires to read and insert into cache every row of the master source before starting to join. The consequence is a higher memory consumption and higher number of input/output (I/O) operations when using the Nested Loop algorithm.

If the input rows are sorted, setting the attribute Sorted Input in the Joiner properties will make the Joiner use the Sorted Merge algorithm. Otherwise, the less efficient Nested Loop algorithm will be used.

More Information
Generic information about the algorithms (not specific to PowerCenter):

Applies To
Product: PowerCenter
Problem Type:
User Type: Administrator
Project Phase:
Product Version:
Database:
Operating System:
Other Software:

Reference

Attachments

Last Modified Date:11/19/2010 3:37 PMID:108465
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