Persistent lookups

I read on the SQL Server 2008 Overview paper that there is a new "SSIS persistent lookup" feature.

Performing lookups is a common operation, especially in data warehousing, where fact records must use lookups to transform business keys to their corresponding surrogates. SQL Server Integration Services (SSIS) will increase the performance of lookups so that it scales to meet the largest tables.

I'd like to know how this is different from the existing 2005 lookup.

Marco Russo

http://www.sqlbi.eu

http://sqlblog.com/blogs/marco_russo

{disclaimer about unreleased software and unconfirmed features that can and will change before the release}

In SQL 2005, when the reference table is large and you are using fully cached mode, sometimes it takes longer to get the data out of reference table (OLEDB data source) and hash it for lookup, than to do the actual lookup on the input data.

In SQL 2008 we plan to allow persisting reference table and hashes, so that the reference table can be loaded faster from a local disk. You would not have to touch database that contains that reference table every time you use the lookup.

{disclaimer about unreleased software and unconfirmed features that can and will change before the release}

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Thank you - I hope to see early a new CTP to try this feature.

Marco