OpenSearch/docs/reference/analysis/tokenizers/classic-tokenizer.asciidoc
Christoph Büscher 25aac4f77f
Remove include_type_name in asciidoc where possible (#37568)
The "include_type_name" parameter was temporarily introduced in #37285 to facilitate
moving the default parameter setting to "false" in many places in the documentation
code snippets. Most of the places can simply be reverted without causing errors.
In this change I looked for asciidoc files that contained the
"include_type_name=true" addition when creating new indices but didn't look
likey they made use of the "_doc" type for mappings. This is mostly the case
e.g. in the analysis docs where index creating often only contains settings. I
manually corrected the use of types in some places where the docs still used an
explicit type name and not the dummy "_doc" type.
2019-01-18 09:34:11 +01:00

265 lines
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[[analysis-classic-tokenizer]]
=== Classic Tokenizer
The `classic` tokenizer is a grammar based tokenizer that is good for English
language documents. This tokenizer has heuristics for special treatment of
acronyms, company names, email addresses, and internet host names. However,
these rules don't always work, and the tokenizer doesn't work well for most
languages other than English:
* It splits words at most punctuation characters, removing punctuation. However, a
dot that's not followed by whitespace is considered part of a token.
* It splits words at hyphens, unless there's a number in the token, in which case
the whole token is interpreted as a product number and is not split.
* It recognizes email addresses and internet hostnames as one token.
[float]
=== Example output
[source,js]
---------------------------
POST _analyze
{
"tokenizer": "classic",
"text": "The 2 QUICK Brown-Foxes jumped over the lazy dog's bone."
}
---------------------------
// CONSOLE
/////////////////////
[source,js]
----------------------------
{
"tokens": [
{
"token": "The",
"start_offset": 0,
"end_offset": 3,
"type": "<ALPHANUM>",
"position": 0
},
{
"token": "2",
"start_offset": 4,
"end_offset": 5,
"type": "<ALPHANUM>",
"position": 1
},
{
"token": "QUICK",
"start_offset": 6,
"end_offset": 11,
"type": "<ALPHANUM>",
"position": 2
},
{
"token": "Brown",
"start_offset": 12,
"end_offset": 17,
"type": "<ALPHANUM>",
"position": 3
},
{
"token": "Foxes",
"start_offset": 18,
"end_offset": 23,
"type": "<ALPHANUM>",
"position": 4
},
{
"token": "jumped",
"start_offset": 24,
"end_offset": 30,
"type": "<ALPHANUM>",
"position": 5
},
{
"token": "over",
"start_offset": 31,
"end_offset": 35,
"type": "<ALPHANUM>",
"position": 6
},
{
"token": "the",
"start_offset": 36,
"end_offset": 39,
"type": "<ALPHANUM>",
"position": 7
},
{
"token": "lazy",
"start_offset": 40,
"end_offset": 44,
"type": "<ALPHANUM>",
"position": 8
},
{
"token": "dog's",
"start_offset": 45,
"end_offset": 50,
"type": "<APOSTROPHE>",
"position": 9
},
{
"token": "bone",
"start_offset": 51,
"end_offset": 55,
"type": "<ALPHANUM>",
"position": 10
}
]
}
----------------------------
// TESTRESPONSE
/////////////////////
The above sentence would produce the following terms:
[source,text]
---------------------------
[ The, 2, QUICK, Brown, Foxes, jumped, over, the, lazy, dog's, bone ]
---------------------------
[float]
=== Configuration
The `classic` tokenizer accepts the following parameters:
[horizontal]
`max_token_length`::
The maximum token length. If a token is seen that exceeds this length then
it is split at `max_token_length` intervals. Defaults to `255`.
[float]
=== Example configuration
In this example, we configure the `classic` tokenizer to have a
`max_token_length` of 5 (for demonstration purposes):
[source,js]
----------------------------
PUT my_index
{
"settings": {
"analysis": {
"analyzer": {
"my_analyzer": {
"tokenizer": "my_tokenizer"
}
},
"tokenizer": {
"my_tokenizer": {
"type": "classic",
"max_token_length": 5
}
}
}
}
}
POST my_index/_analyze
{
"analyzer": "my_analyzer",
"text": "The 2 QUICK Brown-Foxes jumped over the lazy dog's bone."
}
----------------------------
// CONSOLE
/////////////////////
[source,js]
----------------------------
{
"tokens": [
{
"token": "The",
"start_offset": 0,
"end_offset": 3,
"type": "<ALPHANUM>",
"position": 0
},
{
"token": "2",
"start_offset": 4,
"end_offset": 5,
"type": "<ALPHANUM>",
"position": 1
},
{
"token": "QUICK",
"start_offset": 6,
"end_offset": 11,
"type": "<ALPHANUM>",
"position": 2
},
{
"token": "Brown",
"start_offset": 12,
"end_offset": 17,
"type": "<ALPHANUM>",
"position": 3
},
{
"token": "Foxes",
"start_offset": 18,
"end_offset": 23,
"type": "<ALPHANUM>",
"position": 4
},
{
"token": "over",
"start_offset": 31,
"end_offset": 35,
"type": "<ALPHANUM>",
"position": 6
},
{
"token": "the",
"start_offset": 36,
"end_offset": 39,
"type": "<ALPHANUM>",
"position": 7
},
{
"token": "lazy",
"start_offset": 40,
"end_offset": 44,
"type": "<ALPHANUM>",
"position": 8
},
{
"token": "dog's",
"start_offset": 45,
"end_offset": 50,
"type": "<APOSTROPHE>",
"position": 9
},
{
"token": "bone",
"start_offset": 51,
"end_offset": 55,
"type": "<ALPHANUM>",
"position": 10
}
]
}
----------------------------
// TESTRESPONSE
/////////////////////
The above example produces the following terms:
[source,text]
---------------------------
[ The, 2, QUICK, Brown, Foxes, jumpe, d, over, the, lazy, dog's, bone ]
---------------------------