[DOCS] Reformat match phrase prefix query (#45209)

This commit is contained in:
James Rodewig 2019-08-06 14:01:49 -04:00
parent fc8a6fc9d0
commit 51c1abc112
2 changed files with 73 additions and 35 deletions

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@ -32,6 +32,7 @@ to the inverted index:
------
[float]
[[specify-index-time-analyzer]]
=== Specifying an index time analyzer
Each <<text,`text`>> field in a mapping can specify its own

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@ -4,27 +4,19 @@
<titleabbrev>Match phrase prefix</titleabbrev>
++++
The `match_phrase_prefix` is the same as `match_phrase`, except that it
allows for prefix matches on the last term in the text. For example:
Returns documents that contain the words of a provided text, in the **same
order** as provided. The last term of the provided text is treated as a
<<query-dsl-prefix-query,prefix>>, matching any words that begin with that term.
[source,js]
--------------------------------------------------
GET /_search
{
"query": {
"match_phrase_prefix" : {
"message" : "quick brown f"
}
}
}
--------------------------------------------------
// CONSOLE
It accepts the same parameters as the phrase type. In addition, it also
accepts a `max_expansions` parameter (default `50`) that can control to how
many suffixes the last term will be expanded. It is highly recommended to set
it to an acceptable value to control the execution time of the query. For
example:
[[match-phrase-prefix-query-ex-request]]
==== Example request
The following search returns documents that contain phrases beginning with
`quick brown f` in the `message` field.
This search would match a `message` value of `quick brown fox` or `two quick
brown ferrets` but not `the fox is quick and brown`.
[source,js]
--------------------------------------------------
@ -33,8 +25,7 @@ GET /_search
"query": {
"match_phrase_prefix" : {
"message" : {
"query" : "quick brown f",
"max_expansions" : 10
"query" : "quick brown f"
}
}
}
@ -42,26 +33,72 @@ GET /_search
--------------------------------------------------
// CONSOLE
[IMPORTANT]
===================================================
The `match_phrase_prefix` query is a poor-man's autocomplete. It is very easy
to use, which lets you get started quickly with _search-as-you-type_ but its
results, which usually are good enough, can sometimes be confusing.
[[match-phrase-prefix-top-level-params]]
==== Top-level parameters for `match_phrase_prefix`
`<field>`::
(Required, object) Field you wish to search.
Consider the query string `quick brown f`. This query works by creating a
phrase query out of `quick` and `brown` (i.e. the term `quick` must exist and
must be followed by the term `brown`). Then it looks at the sorted term
dictionary to find the first 50 terms that begin with `f`, and
adds these terms to the phrase query.
[[match-phrase-prefix-field-params]]
==== Parameters for `<field>`
`query`::
+
--
(Required, string) Text you wish to find in the provided `<field>`.
The `match_phrase_prefix` query <<analysis,analyzes>> any provided text into
tokens before performing a search. The last term of this text is treated as a
<<query-dsl-prefix-query,prefix>>, matching any words that begin with that term.
--
`analyzer`::
(Optional, string) <<analysis,Analyzer>> used to convert text in the `query`
value into tokens. Defaults to the <<specify-index-time-analyzer,index-time
analyzer>> mapped for the `<field>`. If no analyzer is mapped, the index's
default analyzer is used.
`max_expansions`::
(Optional, integer) Maximum number of terms to which the last provided term of
the `query` value will expand. Defaults to `50`.
`slop`::
(Optional, integer) Maximum number of positions allowed between matching tokens.
Defaults to `0`. Transposed terms have a slop of `2`.
`zero_terms_query`::
+
--
(Optional, string) Indicates whether no documents are returned if the `analyzer`
removes all tokens, such as when using a `stop` filter. Valid values are:
`none` (Default)::
No documents are returned if the `analyzer` removes all tokens.
`all`::
Returns all documents, similar to a <<query-dsl-match-all-query,`match_all`>>
query.
--
[[match-phrase-prefix-query-notes]]
==== Notes
[[match-phrase-prefix-autocomplete]]
===== Using the match phrase prefix query for search autocompletion
While easy to set up, using the `match_phrase_prefix` query for search
autocompletion can sometimes produce confusing results.
For example, consider the query string `quick brown f`. This query works by
creating a phrase query out of `quick` and `brown` (i.e. the term `quick` must
exist and must be followed by the term `brown`). Then it looks at the sorted
term dictionary to find the first 50 terms that begin with `f`, and adds these
terms to the phrase query.
The problem is that the first 50 terms may not include the term `fox` so the
phrase `quick brown fox` will not be found. This usually isn't a problem as
phrase `quick brown fox` will not be found. This usually isn't a problem as
the user will continue to type more letters until the word they are looking
for appears.
For better solutions for _search-as-you-type_ see the
<<completion-suggester,completion suggester>> and
the <<search-as-you-type,`search_as_you_type` field type>>.
===================================================