Google Search Appliance Protocol Reference - Manual (Page 31)

Google Search Appliance: Search Protocol Reference Request Format 31
Automatic Filtering
Google uses automatic filtering to ensure the highest quality search results.
Google search uses two types of automatic filters:
• Duplicate Snippet Filter—If multiple documents contain identical titles as well as the same
information in their snippets in response to a query, only the most relevant document of that set is
displayed in the results.
• Duplicate Directory Filter—If there are many results in a single web directory, then only the two
most relevant results for that directory are displayed. An output flag indicates that more results are
available from that directory.
By default, both of these filters are enabled. You can disable or enable the filters by using the filter
parameter settings as shown in the table.
When a search filter is enabled and removes some results, the search results output indicates that
results were filtered. See “Appendix A: Estimated vs. Actual Number of Results” on page 105 for more
information about how a filtered result set is identified and for recommendations for displaying the
results.
Although the filter=0 option exists, Google recommends against setting filter=0 for typical search
requests, because filtering significantly enhances the quality of most search results.
For queries that contain the site special query term or the as_sitesearch query parameter,
automatic filtering does not take place.
When the Google Search Appliance filters results, the top 1000 most relevant URLs are found before the
filters are applied. A URL that is beyond the top 1000 most relevant results is not affected if you change
the filter settings.
Language Filters
Language filters limit a search to pages in the specified languages. The Google Search Appliance has
built-in language filters that detect the language of a query and return appropriate results. You can
combine language filters to further restrict search results.
Note: When the search appliance receives a language-restricted search request for which there are no
results in the languages specified by a filter, it displays search results in all languages.
This section covers:
• “Automatic Language Filters” on page 32
• “Combining Language Filters” on page 34
Filter value Duplicate Snippet Filter Duplicate Directory Filter
filter=1 Enabled (ON) Enabled (ON)
filter=0 Disabled (OFF) Disabled (OFF)
filter=s Disabled (OFF) Enabled (ON)
filter=p Enabled (ON) Disabled (OFF)