本地英文版地址: ../en/analysis-pattern-tokenizer.html
Pattern Tokenizeredit
The pattern tokenizer uses a regular expression to either split text into
terms whenever it matches a word separator, or to capture matching text as
terms.
The default pattern is \W+, which splits text whenever it encounters
non-word characters.
Beware of Pathological Regular Expressions
The pattern tokenizer uses Java Regular Expressions.
A badly written regular expression could run very slowly or even throw a StackOverflowError and cause the node it is running on to exit suddenly.
Read more about pathological regular expressions and how to avoid them.
Example outputedit
POST _analyze
{
"tokenizer": "pattern",
"text": "The foo_bar_size's default is 5."
}
The above sentence would produce the following terms:
[ The, foo_bar_size, s, default, is, 5 ]
Configurationedit
The pattern tokenizer accepts the following parameters:
|
|
A Java regular expression, defaults to |
|
|
Java regular expression flags.
Flags should be pipe-separated, eg |
|
|
Which capture group to extract as tokens. Defaults to |
Example configurationedit
In this example, we configure the pattern tokenizer to break text into
tokens when it encounters commas:
PUT my_index
{
"settings": {
"analysis": {
"analyzer": {
"my_analyzer": {
"tokenizer": "my_tokenizer"
}
},
"tokenizer": {
"my_tokenizer": {
"type": "pattern",
"pattern": ","
}
}
}
}
}
POST my_index/_analyze
{
"analyzer": "my_analyzer",
"text": "comma,separated,values"
}
The above example produces the following terms:
[ comma, separated, values ]
In the next example, we configure the pattern tokenizer to capture values
enclosed in double quotes (ignoring embedded escaped quotes \"). The regex
itself looks like this:
"((?:\\"|[^"]|\\")*)"
And reads as follows:
-
A literal
" -
Start capturing:
-
A literal
\"OR any character except" - Repeat until no more characters match
-
A literal
-
A literal closing
"
When the pattern is specified in JSON, the " and \ characters need to be
escaped, so the pattern ends up looking like:
\"((?:\\\\\"|[^\"]|\\\\\")+)\"
PUT my_index
{
"settings": {
"analysis": {
"analyzer": {
"my_analyzer": {
"tokenizer": "my_tokenizer"
}
},
"tokenizer": {
"my_tokenizer": {
"type": "pattern",
"pattern": "\"((?:\\\\\"|[^\"]|\\\\\")+)\"",
"group": 1
}
}
}
}
}
POST my_index/_analyze
{
"analyzer": "my_analyzer",
"text": "\"value\", \"value with embedded \\\" quote\""
}
The above example produces the following two terms:
[ value, value with embedded \" quote ]