Refiners are cool, whether you are using SharePoint Search or FAST. I like them because they give me so many options and offer so much power to
But a very common question comes up around Refiners, with regard to deep and shallow behavior. I'm sure you know the definition well: FAST Search for SharePoint has
deep refiners, which means that each result in the result set is processed and used when calculating the refiners. However, SharePoint Search uses shallow
refiners, where the refiner values are calculated from the first 50 results only.
These definitions are easy, right? But let’s think a bit ahead and try to answer the question that pops up at almost every conference: Why are some
Refiner values not visible when you're searching? Moreover, why are they visible when you run Query1 and hidden when you run Query2?
For example, let’s say you have a lot of documents crawled, and you enter a query where the result set contains many, many items--thousands, tens of
thousands, or even more. Let’s say you have some Excel workbooks in the result set that might be relevant for you, but this Excel file is not boosted in the
result set at all,. Let’s say the first Excel result is at the 51st position. (You have a lot of Word, PowerPoint, PDF, etc. files on the positions 1-50.)
What happens if you use FAST Search? As the refiners are deep, each result will be processed, including your Excel workbook. For example, in the Result
Type refiner, you’ll see all the Word, PowerPoint, and PDF file types, as well as Excel, as shown in Figure 1. The easy way is you can click on the Excel refiner, and you’ll get
what you’re looking for immediately.
Figure 1: Results include Excel
But what if you don’t have FAST Search, only SharePoint? As only the first 50 results are processed for the refiner calculation, your Excel workbook will
not be included. This means, the Result Type refiner displays the Word, PowerPoint, and PDF refiners but will not display the Excel at all, because it is not
among the top 50 results. As Figure 2 illustrates, you'll see the Result Type refiner as if it there weren't any Excel result at all!
Figure 2: No Excel results
The difference between the shallow and deep refiners doesn’t seem to be so important at first glance, but you have to be aware there’s a
huge difference in the results you'll get in a real production environment. You and your users might have some hidden refiners, and sometimes it’s hard to understand why.
In other words, if a refiner value shows up on your Refinement Panel, that means:
In case of FAST Search for SharePoint (deep refiner): At least one item matches this refiner value in the whole result set. The exact
number of the items matching the refiner value is included.
In the case of SharePoint Search (shallow refiner): At least one item matches this refiner value in the first 50 results.
If you cannot see a specific value on the Refiner Panel, that means:
In case of SharePoint Search (shallow refiner): No result matches this refiner in the first 50 results.