• Full caching (default): loads the entire reference dataset into memory before the lookups begin.
• Partial caching: loads a subset of the reference dataset into memory (which can be constrained to a specific size), queries the source database when a lookup match isn't found in the existing cache, and loads new rows into the cache if a match is found in the source database.
• No caching: the source dataset is queried for each row in the pipeline.

While you can tune the caching for the lookup to get optimal performance, that cache goes away. So if you have a second package that needs to lookup to the same reference table, you have to pay the overhead cost of loading up the cache (if you're using it) again. That's where SQL Server 2008 comes to the rescue with "persistent lookups."

The new Lookup transformation hasn't been made available yet in a public CTP, so I haven't had a chance to benchmark the caching, but I think the improvement of persistent lookups shows promise. Here's my understanding of this feature (which of course is subject to change before SQL Server 2008 goes RTM):

• Caching as it was in SQL Server 2005 continues to work as described with full, partial, and no cache (only better).
• A new type of cache - a "persistent" cache - can be created and re-used.

One big change to caching in general is that you can have a cache larger than 4GB, on both 32-bit and 64-bit systems which should help the scalability of your Lookups.

Let's explore the idea of a persistent cache further. Obviously, it's not useful when the reference dataset is highly volatile. But for a relatively stable reference dataset, it's got possibilities. Essentially, you start the process by populating the cache. You can do this in a separate data flow from the one containing your Lookup transformation. The cache stays in memory to be used by as many Lookups as you like until the package stops executing.

But wait - there's more! As an alternative, you could populate the cache in its own package and store it in a .caw file. Then that cache file can be used in as many other packages as needed. Here's the resusability factor that was missing in SQL Server 2005. The .caw file can be read faster into memory than reading in a table, view, or query for a full cache. It's like the Raw File you can use for asynchronous processing and optimized for reads by Integration Services. In fact, you can use the Raw File Source to load the cache contents into a data flow, do whatchya gotta do to the data, and land the results someplace else if you use the data for more than just Lookups.

Another benefit of storing the cache in a file is the ability to deploy a package to multiple environments and ensure the contents of each cache are identical. Simply add it to the Miscellaneous folder and the package deployment utility will include it in the set of files to be transferred to each target server.

An important change with partial caching is the ability to store rows in the cache that don't match rows in the data flow. You will even be able to specify how much of the cache you want to devote to this purpose.

Considering a considerable part of the ETL process in data warehousing depends on the Lookup transformation, it's good to see this part of Integration Services has received attention in the next release of SQL Server. Watch for the new Lookup transformation, Cache transformation, and Cache connection manager in a future CTP. --Stacia

As I was slogging through updating reports for a client recently, I was really wishing I could fast-forward in time, install SQL Server 2008 in my client's environment, and use the new report designer demonstrated by Jason Carlson (Product Unit Manager of Reporting Services at Microsoft) at PASS 2007 in Denver a few weeks ago. In particular, the 2000/2005 report designer interface isn't very friendly when you want to work with matrix subtotal properties. When I teach Reporting Services classes, I often ask students to come up with a name for the green triangle that is the single point of entry to the Subtotal properties. No one has yet come up with anything better than "that green thingie...". Somehow that strikes me as so much more amusing than the more matter-of-fact "green triangle." (But then I'm easily amused...) I've been creating reports in Reporting Services for at least 4 years now and still have yet to master the precise click-motion required to nail that green thingie the first time. Compound that with trying to accomplish this feat over a Remote Desktop Connection and I was quickly frustrated before I had finished updating the first report! Only twenty more to go...sigh.

While Katmai won't help me with my current problem, I am delighted to see that it will resolve one of the most frustrating aspects of working with the matrix data region. I haven't done an official count, but I do believe I use a matrix much more often than a table, so my encounters with the green thingie are more numerous than I would like. I suspect many other people are frequent users of the matrix and therefore feel my pain. Fortunately, our collective frustration goes away as soon as Katmai releases (and we can convince everyone to make the leap right away - I AM an optimist after all!).

In fact, not only does the matrix improve, the whole report designer interface changes. The version that Jason showed at PASS was a separate client tool - outside of Visual Studio, that is - which he said will ultimately be merged with Report Builder (but don't expect that to happen in the Katmai release). The beautiful thing about the report designer is that it's less intimidating to non-developer types than the Visual Studio report designer interface. The Properties window is still there for the hard-core folks. For everyone else, a right-click will get you what you need. There's also definitely an Office 2007 flavor to the new designer, including ribbons. Business users who are responsible for report development will LOVE this tool.

I have to say it all looks pretty, but my personal favorite is the disappearance of the green thingie. Nothing personal, but good riddance. Subtotal areas in a matrix will now have a place right alongside every other object you place in the designer. And you can use subtotal areas a lot more flexibly, too, because a matrix is no longer really a matrix. Now it's a tablix. (Is that tay-blicks with a long a or tab-blicks with a short a.....?) More about tablix in a future blog entry. Watch for the new report designer in a future CTP release. --Stacia

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