Friday, February 26, 2010

Performance by lookup

1)We use Lookup transformations that query the largest amounts of data to improve overall performance. By doing that we can reduce the number of lookups on the same table.

2)If a mapping contains Lookup transformations, we will enable lookup caching if this option is not enabled .
We will use a persistent cache to improve performance of the lookup whenever possible.
We will explore the possibility of using concurrent caches to improve session performance.
We will use the Lookup SQL Override option to add a WHERE clause to the default SQL statement if it is not defined
We will add ORDER BY clause in lookup SQL statement if there is no order by defined.
We will use SQL override to suppress the default ORDER BY statement and enter an override ORDER BY with fewer columns. Indexing the Lookup Table
We can improve performance for the following types of lookups:
For cached lookups, we will index the lookup table using the columns in the lookup ORDER BY statement.
For Un-cached lookups, we will Index the lookup table using the columns in the lookup where condition.

3)In some cases we use lookup instead of Joiner as lookup is faster than joiner in some cases when lookup contains the master data only.

4)This lookup helps in terms of performance tuning of the mappings also.

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