Apache Solr Reference Guide Covering Apache Solr 6.0

against the phrase fields. (This will work only for boosting documents, not actually for matching.) However, that
phrase query can have a 'slop,' which is the distance between the terms of the query while still considering it a
phrase match. For example:
q=foo bar
qf=field1^5 field2^10
pf=field1^50 field2^20
defType=dismax
With these parameters, the Dismax Query Parser generates a query that looks something like this:
(+(field1:foo^5 OR field2:foo^10) AND (field1:bar^5 OR field2:bar^10))
But it also generates another query that will only be used for boosting results:
field1:"foo bar"^50 OR field2:"foo bar"^20
Thus, any document that has the terms "foo" and "bar" will match; however if some of those documents have
both of the terms as a phrase, it will score much higher because it's more relevant.
If you add the parameter ps (phrase slop), the second query will instead be:
ps=10 field1:"foo bar"~10^50 OR field2:"foo bar"~10^20
This means that if the terms "foo" and "bar" appear in the document with less than 10 terms between each other,
the phrase will match. For example the doc that says:
*Foo* term1 term2 term3 *bar*
will match the phrase query.
How does one use phrase slop? Usually it is configured in the request handler (in solrconfig).
With query slop ( qs) the concept is similar, but it applies to explicit phrase queries from the user. For example, if
you want to search for a name, you could enter:
q="Hans Anderson"
A document that contains "Hans Anderson" will match, but a document that contains the middle name "Christian"
or where the name is written with the last name first ("Anderson, Hans") won't. For those cases one could
configure the query field qs, so that even if the user searches for an explicit phrase query, a slop is applied.
Finally, edismax contains not only a phrase fields ( pf) parameters, but also phrase and query fields 2 and 3.
You can use those fields for setting different fields or boosts. Each of those can use a different phrase slop.
Using the 'magic fields' _val_ and _query_
If the 'magic field' name _val_ is used in a term or phrase query, the value is parsed as a function.
The Solr Query Parser's use of _val_ and _query_ differs from the Lucene Query Parser in the following ways:
If the magic field name _val_ is used in a term or phrase query, the value is parsed as a function.
It provides a hook into FunctionQuery syntax. Quotes are necessary to encapsulate the function when
Apache Solr Reference Guide 6.0
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