How do I do a partial match in Elasticsearch?
JsonRegexParsingUrlElasticsearchJson Problem Overview
I have a link like http://drive.google.com and I want to match "google" out of the link.
I have:
query: {
bool : {
must: {
match: { text: 'google'}
}
}
}
But this only matches if the whole text is 'google' (case insensitive, so it also matches Google or GooGlE etc). How do I match for the 'google' inside of another string?
Json Solutions
Solution 1 - Json
The point is that the ElasticSearch regex you are using requires a full string match:
>Lucene’s patterns are always anchored. The pattern provided must match the entire string.
Thus, to match any character (but a newline), you can use .*
pattern:
match: { text: '.*google.*'}
^^ ^^
In ES6+, use regexp
insted of match
:
"query": {
"regexp": { "text": ".*google.*"}
}
One more variation is for cases when your string can have newlines: match: { text: '(.|\n)*google(.|\n)*'}
. This awful (.|\n)*
is a must in ElasticSearch because this regex flavor does not allow any [\s\S]
workarounds, nor any DOTALL/Singleline flags. "The Lucene regular expression engine is not Perl-compatible but supports a smaller range of operators."
However, if you do not plan to match any complicated patterns and need no word boundary checking, regex search for a mere substring is better performed with a mere wildcard search:
{
"query": {
"wildcard": {
"text": {
"value": "*google*",
"boost": 1.0,
"rewrite": "constant_score"
}
}
}
}
See Wildcard search for more details.
NOTE: The wildcard pattern also needs to match the whole input string, thus
google*
finds all strings starting withgoogle
*google*
finds all strings containinggoogle
*google
finds all strings ending withgoogle
Also, bear in mind the only pair of special characters in wildcard patterns:
?, which matches any single character
*, which can match zero or more characters, including an empty one
Solution 2 - Json
use wildcard query:
'{"query":{ "wildcard": { "text.keyword" : "*google*" }}}'
Solution 3 - Json
For both partial and full text matching ,the following worked
"query" : {
"query_string" : {
"query" : "*searchText*",
"fields" : [
"fieldName"
]
}
Solution 4 - Json
I can't find a breaking change disabling regular expressions in match
, but match: { text: '.*google.*'}
does not work on any of my Elasticsearch 6.2 clusters. Perhaps it is configurable?
Regexp works:
"query": {
"regexp": { "text": ".*google.*"}
}
Solution 5 - Json
For partial matching you can either use prefix or match_phrase_prefix.
Solution 6 - Json
For a more generic solution you can look into using a different analyzer or defining your own. I am assuming you are using the standard analyzer which would split http://drive.google.com into the tokens "http" and "drive.google.com". This is why the search for just google isn't working because it is trying to compare it to the full "drive.google.com".
If instead you indexed your documents using the simple analyzer it would split it up into "http", "drive", "google", and "com". This will allow you to match anyone of those terms on their own.
Solution 7 - Json
using node.js client
tag_name is the field name, value is the incoming search value.
const { body } = await elasticWrapper.client.search({
index: ElasticIndexs.Tags,
body: {
query: {
wildcard: {
tag_name: {
value: `*${value}*`,
boost: 1.0,
rewrite: 'constant_score',
},
},
},
},
});