OpenSearch/docs/reference/ml/anomaly-detection/apis/find-file-structure.asciidoc

[role="xpack"]
[testenv="basic"]
[[ml-find-file-structure]]
=== Find file structure API
++++
<titleabbrev>Find file structure</titleabbrev>
++++

experimental[]

Finds the structure of a text file. The text file must contain data that is
suitable to be ingested into {es}.

[[ml-find-file-structure-request]]
==== {api-request-title}

`POST _ml/find_file_structure`

[[ml-find-file-structure-prereqs]]
==== {api-prereq-title}

* If the {es} {security-features} are enabled, you must have `monitor_ml` or
`monitor` cluster privileges to use this API. See
<<security-privileges>>.

[[ml-find-file-structure-desc]]
==== {api-description-title}

This API provides a starting point for ingesting data into {es} in a format that
is suitable for subsequent use with other {ml} functionality.

Unlike other {es} endpoints, the data that is posted to this endpoint does not
need to be UTF-8 encoded and in JSON format. It must, however, be text; binary
file formats are not currently supported.

The response from the API contains:

* A couple of messages from the beginning of the file.
* Statistics that reveal the most common values for all fields detected within
  the file and basic numeric statistics for numeric fields.
* Information about the structure of the file, which is useful when you write
  ingest configurations to index the file contents.
* Appropriate mappings for an {es} index, which you could use to ingest the file
  contents.

All this information can be calculated by the structure finder with no guidance.
However, you can optionally override some of the decisions about the file
structure by specifying one or more query parameters.

Details of the output can be seen in the
<<ml-find-file-structure-examples,examples>>.

If the structure finder produces unexpected results for a particular file,
specify the `explain` query parameter. It causes an `explanation` to appear in
the response, which should help in determining why the returned structure was
chosen.

[[ml-find-file-structure-query-parms]]
==== {api-query-parms-title}

`charset`::
  (string) Optional. The file's character set. It must be a character set that
  is supported by the JVM that {es} uses. For example, `UTF-8`, `UTF-16LE`,
  `windows-1252`, or `EUC-JP`. If this parameter is not specified, the structure
  finder chooses an appropriate character set.

`column_names`::
  (string) Optional. If you have set `format` to `delimited`, you can specify
  the column names in a comma-separated list. If this parameter is not specified,
  the structure finder uses the column names from the header row of the file. If
  the file does not have a header role, columns are named "column1", "column2",
  "column3", etc.

`delimiter`::
  (string) Optional. If you have set `format` to `delimited`, you can specify
  the character used to delimit the values in each row. Only a single character
  is supported; the delimiter cannot have multiple characters. If this parameter
  is not specified, the structure finder considers the following possibilities:
  comma, tab, semi-colon, and pipe (`|`).

`explain`::
  (boolean) Optional. If this parameter is set to `true`, the response includes
  a field named `explanation`, which is an array of strings that indicate how
  the structure finder produced its result. The default value is `false`.

`format`::
  (string) Optional. The high level structure of the file. Valid values are
  `ndjson`, `xml`, `delimited`, and `semi_structured_text`. If this parameter is
  not specified, the structure finder chooses one.

`grok_pattern`::
  (string) Optional. If you have set `format` to `semi_structured_text`, you can
  specify a Grok pattern that is used to extract fields from every message in
  the file. The name of the timestamp field in the Grok pattern must match what
  is specified in the `timestamp_field` parameter. If that parameter is not
  specified, the name of the timestamp field in the Grok pattern must match
  "timestamp". If `grok_pattern` is not specified, the structure finder creates
  a Grok pattern.

`has_header_row`::
  (boolean) Optional. If you have set `format` to `delimited`, you can use this
  parameter to indicate whether the column names are in the first row of the
  file. If this parameter is not specified, the structure finder guesses based
  on the similarity of the first row of the file to other rows.

`line_merge_size_limit`::
  (unsigned integer) Optional. The maximum number of characters in a message
  when lines are merged to form messages while analyzing semi-structured files.
  The default is `10000`. If you have extremely long messages you may need to
  increase this, but be aware that this may lead to very long processing times
  if the way to group lines into messages is misdetected.

`lines_to_sample`::
  (unsigned integer) Optional. The number of lines to include in the structural
  analysis, starting from the beginning of the file. The minimum is 2; the
  default is `1000`. If the value of this parameter is greater than the number
  of lines in the file, the analysis proceeds (as long as there are at least two
  lines in the file) for all of the lines. +
+
--
NOTE: The number of lines and the variation of the lines affects the speed of
the analysis. For example, if you upload a log file where the first 1000 lines
are all variations on the same message, the analysis will find more commonality
than would be seen with a bigger sample. If possible, however, it is more
efficient to upload a sample file with more variety in the first 1000 lines than
to request analysis of 100000 lines to achieve some variety.
--

`quote`::
  (string) Optional. If you have set `format` to `delimited`, you can specify
  the character used to quote the values in each row if they contain newlines or
  the delimiter character. Only a single character is supported. If this
  parameter is not specified, the default value is a double quote (`"`). If your
  delimited file format does not use quoting, a workaround is to set this
  argument to a character that does not appear anywhere in the sample.

`should_trim_fields`::
  (boolean) Optional. If you have set `format` to `delimited`, you can specify
  whether values between delimiters should have whitespace trimmed from them. If
  this parameter is not specified and the delimiter is pipe (`|`), the default
  value is `true`. Otherwise, the default value is `false`.

`timeout`::
  (time) Optional. Sets the maximum amount of time that the structure analysis
  make take. If the analysis is still running when the timeout expires then it
  will be aborted. The default value is 25 seconds.

`timestamp_field`::
  (string) Optional. The name of the field that contains the primary timestamp
  of each record in the file. In particular, if the file were ingested into an
  index, this is the field that would be used to populate the `@timestamp` field.
+
--
If the `format` is `semi_structured_text`, this field must match the name of the
appropriate extraction in the `grok_pattern`. Therefore, for semi-structured
file formats, it is best not to specify this parameter unless `grok_pattern` is
also specified.

For structured file formats, if you specify this parameter, the field must exist
within the file.

If this parameter is not specified, the structure finder makes a decision about which
field (if any) is the primary timestamp field. For structured file formats, it
is not compulsory to have a timestamp in the file.
--

`timestamp_format`::
  (string) Optional. The Java time format of the timestamp field in the file. +
+
--
NOTE: Only a subset of Java time format letter groups are supported:

* `a`
* `d`
* `dd`
* `EEE`
* `EEEE`
* `H`
* `HH`
* `h`
* `M`
* `MM`
* `MMM`
* `MMMM`
* `mm`
* `ss`
* `XX`
* `XXX`
* `yy`
* `yyyy`
* `zzz`

Additionally `S` letter groups (fractional seconds) of length one to nine are
supported providing they occur after `ss` and separated from the `ss` by a `.`,
`,` or `:`. Spacing and punctuation is also permitted with the exception of `?`,
newline and carriage return, together with literal text enclosed in single
quotes. For example, `MM/dd HH.mm.ss,SSSSSS 'in' yyyy` is a valid override
format.

One valuable use case for this parameter is when the format is semi-structured
text, there are multiple timestamp formats in the file, and you know which
format corresponds to the primary timestamp, but you do not want to specify the
full `grok_pattern`. Another is when the timestamp format is one that the
structure finder does not consider by default.

If this parameter is not specified, the structure finder chooses the best
format from a built-in set.

--

[[ml-find-file-structure-request-body]]
==== {api-request-body-title}

The text file that you want to analyze. It must contain data that is suitable to
be ingested into {es}. It does not need to be in JSON format and it does not
need to be UTF-8 encoded. The size is limited to the {es} HTTP receive buffer
size, which defaults to 100 Mb.

[[ml-find-file-structure-examples]]
==== {api-examples-title}

Suppose you have a newline-delimited JSON file that contains information about
some books. You can send the contents to the `find_file_structure` endpoint:

[source,console]
----
POST _ml/find_file_structure
{"name": "Leviathan Wakes", "author": "James S.A. Corey", "release_date": "2011-06-02", "page_count": 561}
{"name": "Hyperion", "author": "Dan Simmons", "release_date": "1989-05-26", "page_count": 482}
{"name": "Dune", "author": "Frank Herbert", "release_date": "1965-06-01", "page_count": 604}
{"name": "Dune Messiah", "author": "Frank Herbert", "release_date": "1969-10-15", "page_count": 331}
{"name": "Children of Dune", "author": "Frank Herbert", "release_date": "1976-04-21", "page_count": 408}
{"name": "God Emperor of Dune", "author": "Frank Herbert", "release_date": "1981-05-28", "page_count": 454}
{"name": "Consider Phlebas", "author": "Iain M. Banks", "release_date": "1987-04-23", "page_count": 471}
{"name": "Pandora's Star", "author": "Peter F. Hamilton", "release_date": "2004-03-02", "page_count": 768}
{"name": "Revelation Space", "author": "Alastair Reynolds", "release_date": "2000-03-15", "page_count": 585}
{"name": "A Fire Upon the Deep", "author": "Vernor Vinge", "release_date": "1992-06-01", "page_count": 613}
{"name": "Ender's Game", "author": "Orson Scott Card", "release_date": "1985-06-01", "page_count": 324}
{"name": "1984", "author": "George Orwell", "release_date": "1985-06-01", "page_count": 328}
{"name": "Fahrenheit 451", "author": "Ray Bradbury", "release_date": "1953-10-15", "page_count": 227}
{"name": "Brave New World", "author": "Aldous Huxley", "release_date": "1932-06-01", "page_count": 268}
{"name": "Foundation", "author": "Isaac Asimov", "release_date": "1951-06-01", "page_count": 224}
{"name": "The Giver", "author": "Lois Lowry", "release_date": "1993-04-26", "page_count": 208}
{"name": "Slaughterhouse-Five", "author": "Kurt Vonnegut", "release_date": "1969-06-01", "page_count": 275}
{"name": "The Hitchhiker's Guide to the Galaxy", "author": "Douglas Adams", "release_date": "1979-10-12", "page_count": 180}
{"name": "Snow Crash", "author": "Neal Stephenson", "release_date": "1992-06-01", "page_count": 470}
{"name": "Neuromancer", "author": "William Gibson", "release_date": "1984-07-01", "page_count": 271}
{"name": "The Handmaid's Tale", "author": "Margaret Atwood", "release_date": "1985-06-01", "page_count": 311}
{"name": "Starship Troopers", "author": "Robert A. Heinlein", "release_date": "1959-12-01", "page_count": 335}
{"name": "The Left Hand of Darkness", "author": "Ursula K. Le Guin", "release_date": "1969-06-01", "page_count": 304}
{"name": "The Moon is a Harsh Mistress", "author": "Robert A. Heinlein", "release_date": "1966-04-01", "page_count": 288}
----

If the request does not encounter errors, you receive the following result:

[source,console-result]
----
{
  "num_lines_analyzed" : 24, <1>
  "num_messages_analyzed" : 24, <2>
  "sample_start" : "{\"name\": \"Leviathan Wakes\", \"author\": \"James S.A. Corey\", \"release_date\": \"2011-06-02\", \"page_count\": 561}\n{\"name\": \"Hyperion\", \"author\": \"Dan Simmons\", \"release_date\": \"1989-05-26\", \"page_count\": 482}\n", <3>
  "charset" : "UTF-8", <4>
  "has_byte_order_marker" : false, <5>
  "format" : "ndjson", <6>
  "timestamp_field" : "release_date", <7>
  "joda_timestamp_formats" : [ <8>
    "ISO8601"
  ],
  "java_timestamp_formats" : [ <9>
    "ISO8601"
  ],
  "need_client_timezone" : true, <10>
  "mappings" : { <11>
    "@timestamp" : {
      "type" : "date"
    },
    "author" : {
      "type" : "keyword"
    },
    "name" : {
      "type" : "keyword"
    },
    "page_count" : {
      "type" : "long"
    },
    "release_date" : {
      "type" : "date",
      "format" : "iso8601"
    }
  },
  "ingest_pipeline" : {
    "description" : "Ingest pipeline created by file structure finder",
    "processors" : [
      {
        "date" : {
          "field" : "release_date",
          "timezone" : "{{ beat.timezone }}",
          "formats" : [
            "ISO8601"
          ]
        }
      }
    ]
  },
  "field_stats" : { <12>
    "author" : {
      "count" : 24,
      "cardinality" : 20,
      "top_hits" : [
        {
          "value" : "Frank Herbert",
          "count" : 4
        },
        {
          "value" : "Robert A. Heinlein",
          "count" : 2
        },
        {
          "value" : "Alastair Reynolds",
          "count" : 1
        },
        {
          "value" : "Aldous Huxley",
          "count" : 1
        },
        {
          "value" : "Dan Simmons",
          "count" : 1
        },
        {
          "value" : "Douglas Adams",
          "count" : 1
        },
        {
          "value" : "George Orwell",
          "count" : 1
        },
        {
          "value" : "Iain M. Banks",
          "count" : 1
        },
        {
          "value" : "Isaac Asimov",
          "count" : 1
        },
        {
          "value" : "James S.A. Corey",
          "count" : 1
        }
      ]
    },
    "name" : {
      "count" : 24,
      "cardinality" : 24,
      "top_hits" : [
        {
          "value" : "1984",
          "count" : 1
        },
        {
          "value" : "A Fire Upon the Deep",
          "count" : 1
        },
        {
          "value" : "Brave New World",
          "count" : 1
        },
        {
          "value" : "Children of Dune",
          "count" : 1
        },
        {
          "value" : "Consider Phlebas",
          "count" : 1
        },
        {
          "value" : "Dune",
          "count" : 1
        },
        {
          "value" : "Dune Messiah",
          "count" : 1
        },
        {
          "value" : "Ender's Game",
          "count" : 1
        },
        {
          "value" : "Fahrenheit 451",
          "count" : 1
        },
        {
          "value" : "Foundation",
          "count" : 1
        }
      ]
    },
    "page_count" : {
      "count" : 24,
      "cardinality" : 24,
      "min_value" : 180,
      "max_value" : 768,
      "mean_value" : 387.0833333333333,
      "median_value" : 329.5,
      "top_hits" : [
        {
          "value" : 180,
          "count" : 1
        },
        {
          "value" : 208,
          "count" : 1
        },
        {
          "value" : 224,
          "count" : 1
        },
        {
          "value" : 227,
          "count" : 1
        },
        {
          "value" : 268,
          "count" : 1
        },
        {
          "value" : 271,
          "count" : 1
        },
        {
          "value" : 275,
          "count" : 1
        },
        {
          "value" : 288,
          "count" : 1
        },
        {
          "value" : 304,
          "count" : 1
        },
        {
          "value" : 311,
          "count" : 1
        }
      ]
    },
    "release_date" : {
      "count" : 24,
      "cardinality" : 20,
      "earliest" : "1932-06-01",
      "latest" : "2011-06-02",
      "top_hits" : [
        {
          "value" : "1985-06-01",
          "count" : 3
        },
        {
          "value" : "1969-06-01",
          "count" : 2
        },
        {
          "value" : "1992-06-01",
          "count" : 2
        },
        {
          "value" : "1932-06-01",
          "count" : 1
        },
        {
          "value" : "1951-06-01",
          "count" : 1
        },
        {
          "value" : "1953-10-15",
          "count" : 1
        },
        {
          "value" : "1959-12-01",
          "count" : 1
        },
        {
          "value" : "1965-06-01",
          "count" : 1
        },
        {
          "value" : "1966-04-01",
          "count" : 1
        },
        {
          "value" : "1969-10-15",
          "count" : 1
        }
      ]
    }
  }
}
----
// TESTRESPONSE[s/"sample_start" : ".*",/"sample_start" : "$body.sample_start",/]
// The substitution is because the "file" is pre-processed by the test harness,
// so the fields may get reordered in the JSON the endpoint sees

<1> `num_lines_analyzed` indicates how many lines of the file were analyzed.
<2> `num_messages_analyzed` indicates how many distinct messages the lines contained.
     For NDJSON, this value is the same as `num_lines_analyzed`. For other file
     formats, messages can span several lines.
<3> `sample_start` reproduces the first two messages in the file verbatim. This
     may help to diagnose parse errors or accidental uploads of the wrong file.
<4> `charset` indicates the character encoding used to parse the file.
<5> For UTF character encodings, `has_byte_order_marker` indicates whether the
    file begins with a byte order marker.
<6> `format` is one of `ndjson`, `xml`, `delimited` or `semi_structured_text`.
<7> The `timestamp_field` names the field considered most likely to be the
    primary timestamp of each document.
<8> `joda_timestamp_formats` are used to tell Logstash how to parse timestamps.
<9> `java_timestamp_formats` are the Java time formats recognized in the time
    fields. Elasticsearch mappings and Ingest pipeline use this format.
<10> If a timestamp format is detected that does not include a timezone,
     `need_client_timezone` will be `true`. The server that parses the file must
     therefore be told the correct timezone by the client.
<11> `mappings` contains some suitable mappings for an index into which the data
     could be ingested. In this case, the `release_date` field has been given a
     `keyword` type as it is not considered specific enough to convert to the
     `date` type.
<12> `field_stats` contains the most common values of each field, plus basic
     numeric statistics for the numeric `page_count` field. This information
     may provide clues that the data needs to be cleaned or transformed prior
     to use by other {ml} functionality.

The next example shows how it's possible to find the structure of some New York
City yellow cab trip data. The first `curl` command downloads the data, the
first 20000 lines of which are then piped into the `find_file_structure`
endpoint. The `lines_to_sample` query parameter of the endpoint is set to 20000
to match what is specified in the `head` command.

[source,js]
----
curl -s "s3.amazonaws.com/nyc-tlc/trip+data/yellow_tripdata_2018-06.csv" | head -20000 | curl -s -H "Content-Type: application/json" -XPOST "localhost:9200/_ml/find_file_structure?pretty&lines_to_sample=20000" -T -
----
// NOTCONSOLE
// Not converting to console because this shows how curl can be used

--
NOTE: The `Content-Type: application/json` header must be set even though in
this case the data is not JSON. (Alternatively the `Content-Type` can be set
to any other supported by Elasticsearch, but it must be set.)
--

If the request does not encounter errors, you receive the following result:

[source,js]
----
{
  "num_lines_analyzed" : 20000,
  "num_messages_analyzed" : 19998, <1>
  "sample_start" : "VendorID,tpep_pickup_datetime,tpep_dropoff_datetime,passenger_count,trip_distance,RatecodeID,store_and_fwd_flag,PULocationID,DOLocationID,payment_type,fare_amount,extra,mta_tax,tip_amount,tolls_amount,improvement_surcharge,total_amount\n\n1,2018-06-01 00:15:40,2018-06-01 00:16:46,1,.00,1,N,145,145,2,3,0.5,0.5,0,0,0.3,4.3\n",
  "charset" : "UTF-8",
  "has_byte_order_marker" : false,
  "format" : "delimited", <2>
  "multiline_start_pattern" : "^.*?,\"?\\d{4}-\\d{2}-\\d{2}[T ]\\d{2}:\\d{2}",
  "exclude_lines_pattern" : "^\"?VendorID\"?,\"?tpep_pickup_datetime\"?,\"?tpep_dropoff_datetime\"?,\"?passenger_count\"?,\"?trip_distance\"?,\"?RatecodeID\"?,\"?store_and_fwd_flag\"?,\"?PULocationID\"?,\"?DOLocationID\"?,\"?payment_type\"?,\"?fare_amount\"?,\"?extra\"?,\"?mta_tax\"?,\"?tip_amount\"?,\"?tolls_amount\"?,\"?improvement_surcharge\"?,\"?total_amount\"?",
  "column_names" : [ <3>
    "VendorID",
    "tpep_pickup_datetime",
    "tpep_dropoff_datetime",
    "passenger_count",
    "trip_distance",
    "RatecodeID",
    "store_and_fwd_flag",
    "PULocationID",
    "DOLocationID",
    "payment_type",
    "fare_amount",
    "extra",
    "mta_tax",
    "tip_amount",
    "tolls_amount",
    "improvement_surcharge",
    "total_amount"
  ],
  "has_header_row" : true, <4>
  "delimiter" : ",", <5>
  "quote" : "\"", <6>
  "timestamp_field" : "tpep_pickup_datetime", <7>
  "joda_timestamp_formats" : [ <8>
    "YYYY-MM-dd HH:mm:ss"
  ],
  "java_timestamp_formats" : [ <9>
    "yyyy-MM-dd HH:mm:ss"
  ],
  "need_client_timezone" : true, <10>
  "mappings" : {
    "@timestamp" : {
      "type" : "date"
    },
    "DOLocationID" : {
      "type" : "long"
    },
    "PULocationID" : {
      "type" : "long"
    },
    "RatecodeID" : {
      "type" : "long"
    },
    "VendorID" : {
      "type" : "long"
    },
    "extra" : {
      "type" : "double"
    },
    "fare_amount" : {
      "type" : "double"
    },
    "improvement_surcharge" : {
      "type" : "double"
    },
    "mta_tax" : {
      "type" : "double"
    },
    "passenger_count" : {
      "type" : "long"
    },
    "payment_type" : {
      "type" : "long"
    },
    "store_and_fwd_flag" : {
      "type" : "keyword"
    },
    "tip_amount" : {
      "type" : "double"
    },
    "tolls_amount" : {
      "type" : "double"
    },
    "total_amount" : {
      "type" : "double"
    },
    "tpep_dropoff_datetime" : {
      "type" : "date",
      "format" : "yyyy-MM-dd HH:mm:ss"
    },
    "tpep_pickup_datetime" : {
      "type" : "date",
      "format" : "yyyy-MM-dd HH:mm:ss"
    },
    "trip_distance" : {
      "type" : "double"
    }
  },
  "ingest_pipeline" : {
    "description" : "Ingest pipeline created by file structure finder",
    "processors" : [
      {
        "date" : {
          "field" : "tpep_pickup_datetime",
          "timezone" : "{{ beat.timezone }}",
          "formats" : [
            "yyyy-MM-dd HH:mm:ss"
          ]
        }
      }
    ]
  },
  "field_stats" : {
    "DOLocationID" : {
      "count" : 19998,
      "cardinality" : 240,
      "min_value" : 1,
      "max_value" : 265,
      "mean_value" : 150.26532653265312,
      "median_value" : 148,
      "top_hits" : [
        {
          "value" : 79,
          "count" : 760
        },
        {
          "value" : 48,
          "count" : 683
        },
        {
          "value" : 68,
          "count" : 529
        },
        {
          "value" : 170,
          "count" : 506
        },
        {
          "value" : 107,
          "count" : 468
        },
        {
          "value" : 249,
          "count" : 457
        },
        {
          "value" : 230,
          "count" : 441
        },
        {
          "value" : 186,
          "count" : 432
        },
        {
          "value" : 141,
          "count" : 409
        },
        {
          "value" : 263,
          "count" : 386
        }
      ]
    },
    "PULocationID" : {
      "count" : 19998,
      "cardinality" : 154,
      "min_value" : 1,
      "max_value" : 265,
      "mean_value" : 153.4042404240424,
      "median_value" : 148,
      "top_hits" : [
        {
          "value" : 79,
          "count" : 1067
        },
        {
          "value" : 230,
          "count" : 949
        },
        {
          "value" : 148,
          "count" : 940
        },
        {
          "value" : 132,
          "count" : 897
        },
        {
          "value" : 48,
          "count" : 853
        },
        {
          "value" : 161,
          "count" : 820
        },
        {
          "value" : 234,
          "count" : 750
        },
        {
          "value" : 249,
          "count" : 722
        },
        {
          "value" : 164,
          "count" : 663
        },
        {
          "value" : 114,
          "count" : 646
        }
      ]
    },
    "RatecodeID" : {
      "count" : 19998,
      "cardinality" : 5,
      "min_value" : 1,
      "max_value" : 5,
      "mean_value" : 1.0656565656565653,
      "median_value" : 1,
      "top_hits" : [
        {
          "value" : 1,
          "count" : 19311
        },
        {
          "value" : 2,
          "count" : 468
        },
        {
          "value" : 5,
          "count" : 195
        },
        {
          "value" : 4,
          "count" : 17
        },
        {
          "value" : 3,
          "count" : 7
        }
      ]
    },
    "VendorID" : {
      "count" : 19998,
      "cardinality" : 2,
      "min_value" : 1,
      "max_value" : 2,
      "mean_value" : 1.59005900590059,
      "median_value" : 2,
      "top_hits" : [
        {
          "value" : 2,
          "count" : 11800
        },
        {
          "value" : 1,
          "count" : 8198
        }
      ]
    },
    "extra" : {
      "count" : 19998,
      "cardinality" : 3,
      "min_value" : -0.5,
      "max_value" : 0.5,
      "mean_value" : 0.4815981598159816,
      "median_value" : 0.5,
      "top_hits" : [
        {
          "value" : 0.5,
          "count" : 19281
        },
        {
          "value" : 0,
          "count" : 698
        },
        {
          "value" : -0.5,
          "count" : 19
        }
      ]
    },
    "fare_amount" : {
      "count" : 19998,
      "cardinality" : 208,
      "min_value" : -100,
      "max_value" : 300,
      "mean_value" : 13.937719771977209,
      "median_value" : 9.5,
      "top_hits" : [
        {
          "value" : 6,
          "count" : 1004
        },
        {
          "value" : 6.5,
          "count" : 935
        },
        {
          "value" : 5.5,
          "count" : 909
        },
        {
          "value" : 7,
          "count" : 903
        },
        {
          "value" : 5,
          "count" : 889
        },
        {
          "value" : 7.5,
          "count" : 854
        },
        {
          "value" : 4.5,
          "count" : 802
        },
        {
          "value" : 8.5,
          "count" : 790
        },
        {
          "value" : 8,
          "count" : 789
        },
        {
          "value" : 9,
          "count" : 711
        }
      ]
    },
    "improvement_surcharge" : {
      "count" : 19998,
      "cardinality" : 3,
      "min_value" : -0.3,
      "max_value" : 0.3,
      "mean_value" : 0.29915991599159913,
      "median_value" : 0.3,
      "top_hits" : [
        {
          "value" : 0.3,
          "count" : 19964
        },
        {
          "value" : -0.3,
          "count" : 22
        },
        {
          "value" : 0,
          "count" : 12
        }
      ]
    },
    "mta_tax" : {
      "count" : 19998,
      "cardinality" : 3,
      "min_value" : -0.5,
      "max_value" : 0.5,
      "mean_value" : 0.4962246224622462,
      "median_value" : 0.5,
      "top_hits" : [
        {
          "value" : 0.5,
          "count" : 19868
        },
        {
          "value" : 0,
          "count" : 109
        },
        {
          "value" : -0.5,
          "count" : 21
        }
      ]
    },
    "passenger_count" : {
      "count" : 19998,
      "cardinality" : 7,
      "min_value" : 0,
      "max_value" : 6,
      "mean_value" : 1.6201620162016201,
      "median_value" : 1,
      "top_hits" : [
        {
          "value" : 1,
          "count" : 14219
        },
        {
          "value" : 2,
          "count" : 2886
        },
        {
          "value" : 5,
          "count" : 1047
        },
        {
          "value" : 3,
          "count" : 804
        },
        {
          "value" : 6,
          "count" : 523
        },
        {
          "value" : 4,
          "count" : 406
        },
        {
          "value" : 0,
          "count" : 113
        }
      ]
    },
    "payment_type" : {
      "count" : 19998,
      "cardinality" : 4,
      "min_value" : 1,
      "max_value" : 4,
      "mean_value" : 1.315631563156316,
      "median_value" : 1,
      "top_hits" : [
        {
          "value" : 1,
          "count" : 13936
        },
        {
          "value" : 2,
          "count" : 5857
        },
        {
          "value" : 3,
          "count" : 160
        },
        {
          "value" : 4,
          "count" : 45
        }
      ]
    },
    "store_and_fwd_flag" : {
      "count" : 19998,
      "cardinality" : 2,
      "top_hits" : [
        {
          "value" : "N",
          "count" : 19910
        },
        {
          "value" : "Y",
          "count" : 88
        }
      ]
    },
    "tip_amount" : {
      "count" : 19998,
      "cardinality" : 717,
      "min_value" : 0,
      "max_value" : 128,
      "mean_value" : 2.010959095909593,
      "median_value" : 1.45,
      "top_hits" : [
        {
          "value" : 0,
          "count" : 6917
        },
        {
          "value" : 1,
          "count" : 1178
        },
        {
          "value" : 2,
          "count" : 624
        },
        {
          "value" : 3,
          "count" : 248
        },
        {
          "value" : 1.56,
          "count" : 206
        },
        {
          "value" : 1.46,
          "count" : 205
        },
        {
          "value" : 1.76,
          "count" : 196
        },
        {
          "value" : 1.45,
          "count" : 195
        },
        {
          "value" : 1.36,
          "count" : 191
        },
        {
          "value" : 1.5,
          "count" : 187
        }
      ]
    },
    "tolls_amount" : {
      "count" : 19998,
      "cardinality" : 26,
      "min_value" : 0,
      "max_value" : 35,
      "mean_value" : 0.2729697969796978,
      "median_value" : 0,
      "top_hits" : [
        {
          "value" : 0,
          "count" : 19107
        },
        {
          "value" : 5.76,
          "count" : 791
        },
        {
          "value" : 10.5,
          "count" : 36
        },
        {
          "value" : 2.64,
          "count" : 21
        },
        {
          "value" : 11.52,
          "count" : 8
        },
        {
          "value" : 5.54,
          "count" : 4
        },
        {
          "value" : 8.5,
          "count" : 4
        },
        {
          "value" : 17.28,
          "count" : 4
        },
        {
          "value" : 2,
          "count" : 2
        },
        {
          "value" : 2.16,
          "count" : 2
        }
      ]
    },
    "total_amount" : {
      "count" : 19998,
      "cardinality" : 1267,
      "min_value" : -100.3,
      "max_value" : 389.12,
      "mean_value" : 17.499898989898995,
      "median_value" : 12.35,
      "top_hits" : [
        {
          "value" : 7.3,
          "count" : 478
        },
        {
          "value" : 8.3,
          "count" : 443
        },
        {
          "value" : 8.8,
          "count" : 420
        },
        {
          "value" : 6.8,
          "count" : 406
        },
        {
          "value" : 7.8,
          "count" : 405
        },
        {
          "value" : 6.3,
          "count" : 371
        },
        {
          "value" : 9.8,
          "count" : 368
        },
        {
          "value" : 5.8,
          "count" : 362
        },
        {
          "value" : 9.3,
          "count" : 332
        },
        {
          "value" : 10.3,
          "count" : 332
        }
      ]
    },
    "tpep_dropoff_datetime" : {
      "count" : 19998,
      "cardinality" : 9066,
      "earliest" : "2018-05-31 06:18:15",
      "latest" : "2018-06-02 02:25:44",
      "top_hits" : [
        {
          "value" : "2018-06-01 01:12:12",
          "count" : 10
        },
        {
          "value" : "2018-06-01 00:32:15",
          "count" : 9
        },
        {
          "value" : "2018-06-01 00:44:27",
          "count" : 9
        },
        {
          "value" : "2018-06-01 00:46:42",
          "count" : 9
        },
        {
          "value" : "2018-06-01 01:03:22",
          "count" : 9
        },
        {
          "value" : "2018-06-01 01:05:13",
          "count" : 9
        },
        {
          "value" : "2018-06-01 00:11:20",
          "count" : 8
        },
        {
          "value" : "2018-06-01 00:16:03",
          "count" : 8
        },
        {
          "value" : "2018-06-01 00:19:47",
          "count" : 8
        },
        {
          "value" : "2018-06-01 00:25:17",
          "count" : 8
        }
      ]
    },
    "tpep_pickup_datetime" : {
      "count" : 19998,
      "cardinality" : 8760,
      "earliest" : "2018-05-31 06:08:31",
      "latest" : "2018-06-02 01:21:21",
      "top_hits" : [
        {
          "value" : "2018-06-01 00:01:23",
          "count" : 12
        },
        {
          "value" : "2018-06-01 00:04:31",
          "count" : 10
        },
        {
          "value" : "2018-06-01 00:05:38",
          "count" : 10
        },
        {
          "value" : "2018-06-01 00:09:50",
          "count" : 10
        },
        {
          "value" : "2018-06-01 00:12:01",
          "count" : 10
        },
        {
          "value" : "2018-06-01 00:14:17",
          "count" : 10
        },
        {
          "value" : "2018-06-01 00:00:34",
          "count" : 9
        },
        {
          "value" : "2018-06-01 00:00:40",
          "count" : 9
        },
        {
          "value" : "2018-06-01 00:02:53",
          "count" : 9
        },
        {
          "value" : "2018-06-01 00:05:40",
          "count" : 9
        }
      ]
    },
    "trip_distance" : {
      "count" : 19998,
      "cardinality" : 1687,
      "min_value" : 0,
      "max_value" : 64.63,
      "mean_value" : 3.6521062106210715,
      "median_value" : 2.16,
      "top_hits" : [
        {
          "value" : 0.9,
          "count" : 335
        },
        {
          "value" : 0.8,
          "count" : 320
        },
        {
          "value" : 1.1,
          "count" : 316
        },
        {
          "value" : 0.7,
          "count" : 304
        },
        {
          "value" : 1.2,
          "count" : 303
        },
        {
          "value" : 1,
          "count" : 296
        },
        {
          "value" : 1.3,
          "count" : 280
        },
        {
          "value" : 1.5,
          "count" : 268
        },
        {
          "value" : 1.6,
          "count" : 268
        },
        {
          "value" : 0.6,
          "count" : 256
        }
      ]
    }
  }
}
----
// NOTCONSOLE

<1> `num_messages_analyzed` is 2 lower than `num_lines_analyzed` because only
    data records count as messages. The first line contains the column names
    and in this sample the second line is blank.
<2> Unlike the first example, in this case the `format` has been identified as
    `delimited`.
<3> Because the `format` is `delimited`, the `column_names` field in the output
    lists the column names in the order they appear in the sample.
<4> `has_header_row` indicates that for this sample the column names were in
    the first row of the sample. (If they hadn't been then it would have been
    a good idea to specify them in the `column_names` query parameter.)
<5> The `delimiter` for this sample is a comma, as it's a CSV file.
<6> The `quote` character is the default double quote. (The structure finder
    does not attempt to deduce any other quote character, so if you have a
    delimited file that's quoted with some other character you must specify it
    using the `quote` query parameter.)
<7> The `timestamp_field` has been chosen to be `tpep_pickup_datetime`.
    `tpep_dropoff_datetime` would work just as well, but `tpep_pickup_datetime`
    was chosen because it comes first in the column order. If you prefer
    `tpep_dropoff_datetime` then force it to be chosen using the
    `timestamp_field` query parameter.
<8> `joda_timestamp_formats` are used to tell Logstash how to parse timestamps.
<9> `java_timestamp_formats` are the Java time formats recognized in the time
    fields. Elasticsearch mappings and Ingest pipeline use this format.
<10> The timestamp format in this sample doesn't specify a timezone, so to
     accurately convert them to UTC timestamps to store in Elasticsearch it's
     necessary to supply the timezone they relate to. `need_client_timezone`
     will be `false` for timestamp formats that include the timezone.

If you try to analyze a lot of data then the analysis will take a long time.
If you want to limit the amount of processing your {es} cluster performs for
a request, use the `timeout` query parameter. The analysis will be aborted and
an error returned when the timeout expires. For example, you can replace 20000
lines in the previous example with 200000 and set a 1 second timeout on the
analysis:

[source,js]
----
curl -s "s3.amazonaws.com/nyc-tlc/trip+data/yellow_tripdata_2018-06.csv" | head -200000 | curl -s -H "Content-Type: application/json" -XPOST "localhost:9200/_ml/find_file_structure?pretty&lines_to_sample=200000&timeout=1s" -T -
----
// NOTCONSOLE
// Not converting to console because this shows how curl can be used

Unless you are using an incredibly fast computer you'll receive a timeout error:

[source,js]
----
{
  "error" : {
    "root_cause" : [
      {
        "type" : "timeout_exception",
        "reason" : "Aborting structure analysis during [delimited record parsing] as it has taken longer than the timeout of [1s]"
      }
    ],
    "type" : "timeout_exception",
    "reason" : "Aborting structure analysis during [delimited record parsing] as it has taken longer than the timeout of [1s]"
  },
  "status" : 500
}
----
// NOTCONSOLE

--
NOTE: If you try the example above yourself you will note that the overall
running time of the `curl` commands is considerably longer than 1 second. This
is because it takes a while to download 200000 lines of CSV from the internet,
and the timeout is measured from the time this endpoint starts to process the
data.
--

This is an example of analyzing {es}'s own log file:

[source,js]
----
curl -s -H "Content-Type: application/json" -XPOST "localhost:9200/_ml/find_file_structure?pretty" -T "$ES_HOME/logs/elasticsearch.log"
----
// NOTCONSOLE
// Not converting to console because this shows how curl can be used

If the request does not encounter errors, the result will look something like
this:

[source,js]
----
{
  "num_lines_analyzed" : 53,
  "num_messages_analyzed" : 53,
  "sample_start" : "[2018-09-27T14:39:28,518][INFO ][o.e.e.NodeEnvironment    ] [node-0] using [1] data paths, mounts [[/ (/dev/disk1)]], net usable_space [165.4gb], net total_space [464.7gb], types [hfs]\n[2018-09-27T14:39:28,521][INFO ][o.e.e.NodeEnvironment    ] [node-0] heap size [494.9mb], compressed ordinary object pointers [true]\n",
  "charset" : "UTF-8",
  "has_byte_order_marker" : false,
  "format" : "semi_structured_text", <1>
  "multiline_start_pattern" : "^\\[\\b\\d{4}-\\d{2}-\\d{2}[T ]\\d{2}:\\d{2}", <2>
  "grok_pattern" : "\\[%{TIMESTAMP_ISO8601:timestamp}\\]\\[%{LOGLEVEL:loglevel}.*", <3>
  "timestamp_field" : "timestamp",
  "joda_timestamp_formats" : [
    "ISO8601"
  ],
  "java_timestamp_formats" : [
    "ISO8601"
  ],
  "need_client_timezone" : true,
  "mappings" : {
    "@timestamp" : {
      "type" : "date"
    },
    "loglevel" : {
      "type" : "keyword"
    },
    "message" : {
      "type" : "text"
    }
  },
  "ingest_pipeline" : {
    "description" : "Ingest pipeline created by file structure finder",
    "processors" : [
      {
        "grok" : {
          "field" : "message",
          "patterns" : [
            "\\[%{TIMESTAMP_ISO8601:timestamp}\\]\\[%{LOGLEVEL:loglevel}.*"
          ]
        }
      },
      {
        "date" : {
          "field" : "timestamp",
          "timezone" : "{{ beat.timezone }}",
          "formats" : [
            "ISO8601"
          ]
        }
      },
      {
        "remove" : {
          "field" : "timestamp"
        }
      }
    ]
  },
  "field_stats" : {
    "loglevel" : {
      "count" : 53,
      "cardinality" : 3,
      "top_hits" : [
        {
          "value" : "INFO",
          "count" : 51
        },
        {
          "value" : "DEBUG",
          "count" : 1
        },
        {
          "value" : "WARN",
          "count" : 1
        }
      ]
    },
    "timestamp" : {
      "count" : 53,
      "cardinality" : 28,
      "earliest" : "2018-09-27T14:39:28,518",
      "latest" : "2018-09-27T14:39:37,012",
      "top_hits" : [
        {
          "value" : "2018-09-27T14:39:29,859",
          "count" : 10
        },
        {
          "value" : "2018-09-27T14:39:29,860",
          "count" : 9
        },
        {
          "value" : "2018-09-27T14:39:29,858",
          "count" : 6
        },
        {
          "value" : "2018-09-27T14:39:28,523",
          "count" : 3
        },
        {
          "value" : "2018-09-27T14:39:34,234",
          "count" : 2
        },
        {
          "value" : "2018-09-27T14:39:28,518",
          "count" : 1
        },
        {
          "value" : "2018-09-27T14:39:28,521",
          "count" : 1
        },
        {
          "value" : "2018-09-27T14:39:28,522",
          "count" : 1
        },
        {
          "value" : "2018-09-27T14:39:29,861",
          "count" : 1
        },
        {
          "value" : "2018-09-27T14:39:32,786",
          "count" : 1
        }
      ]
    }
  }
}
----
// NOTCONSOLE

<1> This time the `format` has been identified as `semi_structured_text`.
<2> The `multiline_start_pattern` is set on the basis that the timestamp appears
    in the first line of each multi-line log message.
<3> A very simple `grok_pattern` has been created, which extracts the timestamp
    and recognizable fields that appear in every analyzed message. In this case
    the only field that was recognized beyond the timestamp was the log level.

If you recognize more fields than the simple `grok_pattern` produced by the
structure finder unaided then you can resubmit the request specifying a more
advanced `grok_pattern` as a query parameter and the structure finder will
calculate `field_stats` for your additional fields.

In the case of the {es} log a more complete Grok pattern is
`\[%{TIMESTAMP_ISO8601:timestamp}\]\[%{LOGLEVEL:loglevel} *\]\[%{JAVACLASS:class} *\] \[%{HOSTNAME:node}\] %{JAVALOGMESSAGE:message}`.
You can analyze the same log file again, submitting this `grok_pattern` as a
query parameter (appropriately URL escaped):

[source,js]
----
curl -s -H "Content-Type: application/json" -XPOST "localhost:9200/_ml/find_file_structure?pretty&format=semi_structured_text&grok_pattern=%5C%5B%25%7BTIMESTAMP_ISO8601:timestamp%7D%5C%5D%5C%5B%25%7BLOGLEVEL:loglevel%7D%20*%5C%5D%5C%5B%25%7BJAVACLASS:class%7D%20*%5C%5D%20%5C%5B%25%7BHOSTNAME:node%7D%5C%5D%20%25%7BJAVALOGMESSAGE:message%7D" -T "$ES_HOME/logs/elasticsearch.log"
----
// NOTCONSOLE
// Not converting to console because this shows how curl can be used

If the request does not encounter errors, the result will look something like
this:

[source,js]
----
{
  "num_lines_analyzed" : 53,
  "num_messages_analyzed" : 53,
  "sample_start" : "[2018-09-27T14:39:28,518][INFO ][o.e.e.NodeEnvironment    ] [node-0] using [1] data paths, mounts [[/ (/dev/disk1)]], net usable_space [165.4gb], net total_space [464.7gb], types [hfs]\n[2018-09-27T14:39:28,521][INFO ][o.e.e.NodeEnvironment    ] [node-0] heap size [494.9mb], compressed ordinary object pointers [true]\n",
  "charset" : "UTF-8",
  "has_byte_order_marker" : false,
  "format" : "semi_structured_text",
  "multiline_start_pattern" : "^\\[\\b\\d{4}-\\d{2}-\\d{2}[T ]\\d{2}:\\d{2}",
  "grok_pattern" : "\\[%{TIMESTAMP_ISO8601:timestamp}\\]\\[%{LOGLEVEL:loglevel} *\\]\\[%{JAVACLASS:class} *\\] \\[%{HOSTNAME:node}\\] %{JAVALOGMESSAGE:message}", <1>
  "timestamp_field" : "timestamp",
  "joda_timestamp_formats" : [
    "ISO8601"
  ],
  "java_timestamp_formats" : [
    "ISO8601"
  ],
  "need_client_timezone" : true,
  "mappings" : {
    "@timestamp" : {
      "type" : "date"
    },
    "class" : {
      "type" : "keyword"
    },
    "loglevel" : {
      "type" : "keyword"
    },
    "message" : {
      "type" : "text"
    },
    "node" : {
      "type" : "keyword"
    }
  },
  "ingest_pipeline" : {
    "description" : "Ingest pipeline created by file structure finder",
    "processors" : [
      {
        "grok" : {
          "field" : "message",
          "patterns" : [
            "\\[%{TIMESTAMP_ISO8601:timestamp}\\]\\[%{LOGLEVEL:loglevel} *\\]\\[%{JAVACLASS:class} *\\] \\[%{HOSTNAME:node}\\] %{JAVALOGMESSAGE:message}"
          ]
        }
      },
      {
        "date" : {
          "field" : "timestamp",
          "timezone" : "{{ beat.timezone }}",
          "formats" : [
            "ISO8601"
          ]
        }
      },
      {
        "remove" : {
          "field" : "timestamp"
        }
      }
    ]
  },
  "field_stats" : { <2>
    "class" : {
      "count" : 53,
      "cardinality" : 14,
      "top_hits" : [
        {
          "value" : "o.e.p.PluginsService",
          "count" : 26
        },
        {
          "value" : "o.e.c.m.MetaDataIndexTemplateService",
          "count" : 8
        },
        {
          "value" : "o.e.n.Node",
          "count" : 7
        },
        {
          "value" : "o.e.e.NodeEnvironment",
          "count" : 2
        },
        {
          "value" : "o.e.a.ActionModule",
          "count" : 1
        },
        {
          "value" : "o.e.c.s.ClusterApplierService",
          "count" : 1
        },
        {
          "value" : "o.e.c.s.MasterService",
          "count" : 1
        },
        {
          "value" : "o.e.d.DiscoveryModule",
          "count" : 1
        },
        {
          "value" : "o.e.g.GatewayService",
          "count" : 1
        },
        {
          "value" : "o.e.l.LicenseService",
          "count" : 1
        }
      ]
    },
    "loglevel" : {
      "count" : 53,
      "cardinality" : 3,
      "top_hits" : [
        {
          "value" : "INFO",
          "count" : 51
        },
        {
          "value" : "DEBUG",
          "count" : 1
        },
        {
          "value" : "WARN",
          "count" : 1
        }
      ]
    },
    "message" : {
      "count" : 53,
      "cardinality" : 53,
      "top_hits" : [
        {
          "value" : "Using REST wrapper from plugin org.elasticsearch.xpack.security.Security",
          "count" : 1
        },
        {
          "value" : "adding template [.monitoring-alerts] for index patterns [.monitoring-alerts-6]",
          "count" : 1
        },
        {
          "value" : "adding template [.monitoring-beats] for index patterns [.monitoring-beats-6-*]",
          "count" : 1
        },
        {
          "value" : "adding template [.monitoring-es] for index patterns [.monitoring-es-6-*]",
          "count" : 1
        },
        {
          "value" : "adding template [.monitoring-kibana] for index patterns [.monitoring-kibana-6-*]",
          "count" : 1
        },
        {
          "value" : "adding template [.monitoring-logstash] for index patterns [.monitoring-logstash-6-*]",
          "count" : 1
        },
        {
          "value" : "adding template [.triggered_watches] for index patterns [.triggered_watches*]",
          "count" : 1
        },
        {
          "value" : "adding template [.watch-history-9] for index patterns [.watcher-history-9*]",
          "count" : 1
        },
        {
          "value" : "adding template [.watches] for index patterns [.watches*]",
          "count" : 1
        },
        {
          "value" : "starting ...",
          "count" : 1
        }
      ]
    },
    "node" : {
      "count" : 53,
      "cardinality" : 1,
      "top_hits" : [
        {
          "value" : "node-0",
          "count" : 53
        }
      ]
    },
    "timestamp" : {
      "count" : 53,
      "cardinality" : 28,
      "earliest" : "2018-09-27T14:39:28,518",
      "latest" : "2018-09-27T14:39:37,012",
      "top_hits" : [
        {
          "value" : "2018-09-27T14:39:29,859",
          "count" : 10
        },
        {
          "value" : "2018-09-27T14:39:29,860",
          "count" : 9
        },
        {
          "value" : "2018-09-27T14:39:29,858",
          "count" : 6
        },
        {
          "value" : "2018-09-27T14:39:28,523",
          "count" : 3
        },
        {
          "value" : "2018-09-27T14:39:34,234",
          "count" : 2
        },
        {
          "value" : "2018-09-27T14:39:28,518",
          "count" : 1
        },
        {
          "value" : "2018-09-27T14:39:28,521",
          "count" : 1
        },
        {
          "value" : "2018-09-27T14:39:28,522",
          "count" : 1
        },
        {
          "value" : "2018-09-27T14:39:29,861",
          "count" : 1
        },
        {
          "value" : "2018-09-27T14:39:32,786",
          "count" : 1
        }
      ]
    }
  }
}
----
// NOTCONSOLE

<1> The `grok_pattern` in the output is now the overridden one supplied in the
    query parameter.
<2> The returned `field_stats` include entries for the fields from the
    overridden `grok_pattern`.

The URL escaping is hard, so if you are working interactively it is best to use
the {ml} UI!