A query that uses a query parser in order to parse its content. Here is an example:
{
"query_string" : {
"default_field" : "content",
"query" : "this AND that OR thus"
}
}
The query_string top level parameters include:
| Parameter | Description |
|---|---|
query |
The actual query to be parsed. |
default_field |
The default field for query terms if no prefix field is specified. Defaults to the _all field. |
default_operator |
The default operator used if no explicit operator is specified. For example, with a default operator of OR, the query capital of Hungary is translated to capital OR of OR Hungary, and with default operator of AND, the same query is translated to capital AND of AND Hungary. The default value is OR. |
analyzer |
The analyzer name used to analyze the query string. |
allow_leading_wildcard |
When set, * or ? are allowed as the first character. Defaults to true. |
lowercase_expanded_terms |
Whether terms of wildcard, prefix, fuzzy, and range queries are to be automatically lower-cased or not (since they are not analyzed). Default it true. |
enable_position_increments |
Set to true to enable position increments in result queries. Defaults to true. |
fuzzy_prefix_length |
Set the prefix length for fuzzy queries. Default is 0. |
fuzzy_min_sim |
Set the minimum similarity for fuzzy queries. Defaults to 0.5 |
phrase_slop |
Sets the default slop for phrases. If zero, then exact phrase matches are required. Default value is 0. |
boost |
Sets the boost value of the query. Defaults to 1.0. |
analyze_wildcard |
By default, wildcards terms in a query string are not analyzed. By setting this value to true, a best effort will be made to analyze those as well. |
auto_generate_phrase_queries |
Default to false. |
minimum_should_match |
A percent value (for example 20%) controlling how many “should” clauses in the resulting boolean query should match. |
When a multi term query is being generated, one can control how it gets rewritten using the rewrite parameter.
Multi Field
The query_string query can also run against multiple fields. The idea of running the query_string query against multiple fields is by internally creating several queries for the same query string, each with default_field that match the fields provided. Since several queries are generated, combining them can be automatically done either using a dis_max query or a simple bool query. For example (the name is boosted by 5 using ^5 notation):
{
"query_string" : {
"fields" : ["content", "name^5"],
"query" : "this AND that OR thus",
"use_dis_max" : true
}
}
When running the query_string query against multiple fields, the following additional parameters are allowed:
| Parameter | Description |
|---|---|
use_dis_max |
Should the queries be combined using dis_max (set it to true), or a bool query (set it to false). Defaults to true. |
tie_breaker |
When using dis_max, the disjunction max tie breaker. Defaults to 0. |
The fields parameter can also include pattern based field names, allowing to automatically expand to the relevant fields (dynamically introduced fields included). For example:
{
"query_string" : {
"fields" : ["content", "name.*^5"],
"query" : "this AND that OR thus",
"use_dis_max" : true
}
}
Syntax Extension
There are several syntax extensions to the Lucene query language.
missing / exists
The _exists_ and _missing_ syntax allows to control docs that have fields that exists within them (have a value) and missing. The syntax is: _exists_:field1, _missing_:field and can be used anywhere a query string is used.
