Data From Field Example - Biasing Down PDFs in Search Results

Thunderstone Search Appliance Manual

Data From Field Example - Biasing Down PDFs in Search Results

Arbitrary document types can be biased down in search results with a combination of Data from Field and Rank Bias settings. For example, the percentage rank of PDFs could be decreased by 2% (to push them lower in relevance-ranked query results).

To accomplish this, first create an Integer Parametric field - either at profile creation or via Tools → Parametric Field Tools - or repurpose an existing numeric field. In this example we will call this field docTypeBias.

Then define a Data from Field rule (under All Walk Settings) as follows:

REX Search: >>=application/pdf==
Replace: -2
From Field: MIME Type
From Meta Field: (Empty)
To Field: docTypeBias

This rule looks for "application/pdf" as the MIME type for each document. If it matches, we set docTypeBias to -2. Also, for improved performance, add docTypeBias to the Compound Index Fields setting.

After doing a New rewalk to fully populate this field, go to Search Settings and set Parametric Search Options → docTypeBias to Sortable and Rank Bias (here) to docTypeBias. This will add docTypeBias to the percentage rank, and thus bias PDFs down by 2%. To bias PDFs up instead, simply set the Replace value in the Data from Field rule to a positive number.