Match Query
editMatch Query
editmatch
queries accept text/numerics/dates, analyzes
them, and constructs a query. For example:
GET /_search { "query": { "match" : { "message" : "this is a test" } } }
Note, message
is the name of a field, you can substitute the name of
any field instead.
match
editThe match
query is of type boolean
. It means that the text
provided is analyzed and the analysis process constructs a boolean query
from the provided text. The operator
flag can be set to or
or and
to control the boolean clauses (defaults to or
). The minimum number of
optional should
clauses to match can be set using the
minimum_should_match
parameter.
Here is an example when providing additional parameters (note the slight
change in structure, message
is the field name):
GET /_search { "query": { "match" : { "message" : { "query" : "this is a test", "operator" : "and" } } } }
The analyzer
can be set to control which analyzer will perform the
analysis process on the text. It defaults to the field explicit mapping
definition, or the default search analyzer.
The lenient
parameter can be set to true
to ignore exceptions caused by
data-type mismatches, such as trying to query a numeric field with a text
query string. Defaults to false
.
Fuzziness
editfuzziness
allows fuzzy matching based on the type of field being queried.
See Fuzziness for allowed settings.
The prefix_length
and
max_expansions
can be set in this case to control the fuzzy process.
If the fuzzy option is set the query will use top_terms_blended_freqs_${max_expansions}
as its rewrite
method the fuzzy_rewrite
parameter allows to control how the query will get
rewritten.
Fuzzy transpositions (ab
→ ba
) are allowed by default but can be disabled
by setting fuzzy_transpositions
to false
.
Note that fuzzy matching is not applied to terms with synonyms, as under the hood these terms are expanded to a special synonym query that blends term frequencies, which does not support fuzzy expansion.
GET /_search { "query": { "match" : { "message" : { "query" : "this is a testt", "fuzziness": "AUTO" } } } }
Zero terms query
editIf the analyzer used removes all tokens in a query like a stop
filter
does, the default behavior is to match no documents at all. In order to
change that the zero_terms_query
option can be used, which accepts
none
(default) and all
which corresponds to a match_all
query.
GET /_search { "query": { "match" : { "message" : { "query" : "to be or not to be", "operator" : "and", "zero_terms_query": "all" } } } }
Cutoff frequency
editThe match query supports a cutoff_frequency
that allows
specifying an absolute or relative document frequency where high
frequency terms are moved into an optional subquery and are only scored
if one of the low frequency (below the cutoff) terms in the case of an
or
operator or all of the low frequency terms in the case of an and
operator match.
This query allows handling stopwords
dynamically at runtime, is domain
independent and doesn’t require a stopword file. It prevents scoring /
iterating high frequency terms and only takes the terms into account if a
more significant / lower frequency term matches a document. Yet, if all
of the query terms are above the given cutoff_frequency
the query is
automatically transformed into a pure conjunction (and
) query to
ensure fast execution.
The cutoff_frequency
can either be relative to the total number of
documents if in the range [0..1)
or absolute if greater or equal to
1.0
.
Here is an example showing a query composed of stopwords exclusively:
GET /_search { "query": { "match" : { "message" : { "query" : "to be or not to be", "cutoff_frequency" : 0.001 } } } }
The cutoff_frequency
option operates on a per-shard-level. This means
that when trying it out on test indexes with low document numbers you
should follow the advice in Relevance is broken.
Synonyms
editThe match
query supports multi-terms synonym expansion with the synonym_graph token filter. When this filter is used, the parser creates a phrase query for each multi-terms synonyms.
For example, the following synonym: "ny, new york" would produce:
(ny OR ("new york"))
It is also possible to match multi terms synonyms with conjunctions instead:
GET /_search { "query": { "match" : { "message": { "query" : "ny city", "auto_generate_synonyms_phrase_query" : false } } } }
The example above creates a boolean query:
(ny OR (new AND york)) city
that matches documents with the term ny
or the conjunction new AND york
.
By default the parameter auto_generate_synonyms_phrase_query
is set to true
.