Search-as-you-type field type
editSearch-as-you-type field type
editThe search_as_you_type
field type is a text-like field that is optimized to
provide out-of-the-box support for queries that serve an as-you-type completion
use case. It creates a series of subfields that are analyzed to index terms
that can be efficiently matched by a query that partially matches the entire
indexed text value. Both prefix completion (i.e matching terms starting at the
beginning of the input) and infix completion (i.e. matching terms at any
position within the input) are supported.
When adding a field of this type to a mapping
PUT my-index-000001 { "mappings": { "properties": { "my_field": { "type": "search_as_you_type" } } } }
This creates the following fields
|
Analyzed as configured in the mapping. If an analyzer is not configured, the default analyzer for the index is used |
|
Wraps the analyzer of |
|
Wraps the analyzer of |
|
Wraps the analyzer of |
The size of shingles in subfields can be configured with the max_shingle_size
mapping parameter. The default is 3, and valid values for this parameter are
integer values 2 - 4 inclusive. Shingle subfields will be created for each
shingle size from 2 up to and including the max_shingle_size
. The
my_field._index_prefix
subfield will always use the analyzer from the shingle
subfield with the max_shingle_size
when constructing its own analyzer.
Increasing the max_shingle_size
will improve matches for queries with more
consecutive terms, at the cost of larger index size. The default
max_shingle_size
should usually be sufficient.
The same input text is indexed into each of these fields automatically, with
their differing analysis chains, when an indexed document has a value for the
root field my_field
.
response = client.index( index: 'my-index-000001', id: 1, refresh: true, body: { my_field: 'quick brown fox jump lazy dog' } ) puts response
PUT my-index-000001/_doc/1?refresh { "my_field": "quick brown fox jump lazy dog" }
The most efficient way of querying to serve a search-as-you-type use case is
usually a multi_match
query of type
bool_prefix
that targets the root
search_as_you_type
field and its shingle subfields. This can match the query
terms in any order, but will score documents higher if they contain the terms
in order in a shingle subfield.
response = client.search( index: 'my-index-000001', body: { query: { multi_match: { query: 'brown f', type: 'bool_prefix', fields: [ 'my_field', 'my_field._2gram', 'my_field._3gram' ] } } } ) puts response
GET my-index-000001/_search { "query": { "multi_match": { "query": "brown f", "type": "bool_prefix", "fields": [ "my_field", "my_field._2gram", "my_field._3gram" ] } } }
{ "took" : 44, "timed_out" : false, "_shards" : { "total" : 1, "successful" : 1, "skipped" : 0, "failed" : 0 }, "hits" : { "total" : { "value" : 1, "relation" : "eq" }, "max_score" : 0.8630463, "hits" : [ { "_index" : "my-index-000001", "_id" : "1", "_score" : 0.8630463, "_source" : { "my_field" : "quick brown fox jump lazy dog" } } ] } }
To search for documents that strictly match the query terms in order, or to
search using other properties of phrase queries, use a
match_phrase_prefix
query on the root
field. A match_phrase
query can also be used
if the last term should be matched exactly, and not as a prefix. Using phrase
queries may be less efficient than using the match_bool_prefix
query.
response = client.search( index: 'my-index-000001', body: { query: { match_phrase_prefix: { my_field: 'brown f' } } } ) puts response
GET my-index-000001/_search { "query": { "match_phrase_prefix": { "my_field": "brown f" } } }
Parameters specific to the search_as_you_type
field
editThe following parameters are accepted in a mapping for the search_as_you_type
field and are specific to this field type
-
max_shingle_size
-
(Optional, integer) Largest shingle size to create. Valid values are
2
(inclusive) to4
(inclusive). Defaults to3
.A subfield is created for each integer between
2
and this value. For example, a value of3
creates two subfields:my_field._2gram
andmy_field._3gram
More subfields enables more specific queries but increases index size.
Parameters of the field type as a text field
editThe following parameters are accepted in a mapping for the search_as_you_type
field due to its nature as a text-like field, and behave similarly to their
behavior when configuring a field of the text
data type. Unless
otherwise noted, these options configure the root fields subfields in
the same way.
-
analyzer
-
The analyzer which should be used for
text
fields, both at index-time and at search-time (unless overridden by thesearch_analyzer
). Defaults to the default index analyzer, or thestandard
analyzer. -
index
-
Should the field be searchable? Accepts
true
(default) orfalse
. -
index_options
-
What information should be stored in the index, for search and highlighting
purposes. Defaults to
positions
. -
norms
-
Whether field-length should be taken into account when scoring queries.
Accepts
true
orfalse
. This option configures the root field and shingle subfields, where its default istrue
. It does not configure the prefix subfield, where it isfalse
. -
store
-
Whether the field value should be stored and retrievable separately from
the
_source
field. Acceptstrue
orfalse
(default). This option only configures the root field, and does not configure any subfields. -
search_analyzer
-
The
analyzer
that should be used at search time ontext
fields. Defaults to theanalyzer
setting. -
search_quote_analyzer
-
The
analyzer
that should be used at search time when a phrase is encountered. Defaults to thesearch_analyzer
setting. -
similarity
-
Which scoring algorithm or similarity should be used. Defaults
to
BM25
. -
term_vector
-
Whether term vectors should be stored for the field. Defaults to
no
. This option configures the root field and shingle subfields, but not the prefix subfield.
Optimization of prefix queries
editWhen making a prefix
query to the root field or
any of its subfields, the query will be rewritten to a
term
query on the ._index_prefix
subfield. This
matches more efficiently than is typical of prefix
queries on text fields,
as prefixes up to a certain length of each shingle are indexed directly as
terms in the ._index_prefix
subfield.
The analyzer of the ._index_prefix
subfield slightly modifies the
shingle-building behavior to also index prefixes of the terms at the end of the
field’s value that normally would not be produced as shingles. For example, if
the value quick brown fox
is indexed into a search_as_you_type
field with
max_shingle_size
of 3, prefixes for brown fox
and fox
are also indexed
into the ._index_prefix
subfield even though they do not appear as terms in
the ._3gram
subfield. This allows for completion of all the terms in the
field’s input.