Local Parameters in Queries
Local parameters are arguments in a Solr request that are specific to a query parameter.
Local parameters provide a way to add meta-data to certain argument types such as query strings. (In Solr documentation, local parameters are sometimes referred to as LocalParams.)
Local parameters are specified as prefixes to arguments. Take the following query argument, for example:
q=solr rocks
We can prefix this query string with local parameters to provide more information to the Standard Query Parser. For example, we can change the default operator type to "AND" and the default field to "title":
q={!q.op=AND df=title}solr rocks
These local parameters would change the query to require a match on both "solr" and "rocks" while searching the "title" field by default.
Basic Syntax of Local Parameters
To specify a local parameter, insert the following before the argument to be modified:
- Begin with
{! - Insert any number of key=value pairs separated by white space
- End with
}and immediately follow with the query argument
You may specify only one local parameters prefix per argument. Values in the key-value pairs may be quoted via single or double quotes, and backslash escaping works within quoted strings.
Query Type Short Form
If a local parameter value appears without a name, it is given the implicit name of "type". This allows short-form representation for the type of query parser to use when parsing a query string. Thus
q={!dismax qf=myfield}solr rocks
is equivalent to:
q={!type=dismax qf=myfield}solr rocks
If no "type" is specified (either explicitly or implicitly) then the lucene parser is used by default. Thus
fq={!df=summary}solr rocks
is equivalent to:
fq={!type=lucene df=summary}solr rocks
Specifying the Parameter Value with the v Key
A special key of v within local parameters is an alternate way to specify the value of that parameter.
q={!dismax qf=myfield}solr rocks
is equivalent to
q={!type=dismax qf=myfield v='solr rocks'}
Parameter Dereferencing
Parameter dereferencing, or indirection, lets you use the value of another argument rather than specifying it directly. This can be used to simplify queries, decouple user input from query parameters, or decouple front-end GUI parameters from defaults set in solrconfig.xml.
q={!dismax qf=myfield}solr rocks
is equivalent to:
q={!type=dismax qf=myfield v=$qq}&qq=solr rocks