druid/docs/content/operations/dump-segment.md

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DumpSegment tool

The DumpSegment tool can be used to dump the metadata or contents of a segment for debugging purposes. Note that the dump is not necessarily a full-fidelity translation of the segment. In particular, not all metadata is included, indexes are not included, and complex metric values may not be complete.

To run the tool, point it at a segment directory and provide a file for writing output:

java io.druid.cli.Main tools dump-segment \
  --directory /home/druid/path/to/segment/ \
  --out /home/druid/output.txt

Output format

Data dumps generated by this tool are newline-separate JSON objects, with one object per line. For example, one line might look like this when pretty-printed:

{
  "__time": 1442018818771,
  "added": 36,
  "channel": "#en.wikipedia",
  "cityName": null,
  "comment": "added project",
  "count": 1,
  "countryIsoCode": null,
  "countryName": null,
  "deleted": 0,
  "delta": 36,
  "isAnonymous": "false",
  "isMinor": "false",
  "isNew": "false",
  "isRobot": "false",
  "isUnpatrolled": "false",
  "iuser": "00001553",
  "metroCode": null,
  "namespace": "Talk",
  "page": "Talk:Oswald Tilghman",
  "regionIsoCode": null,
  "regionName": null,
  "user": "GELongstreet"
}

Metadata dumps generated by this tool are in the same format as returned by the SegmentMetadata query.

Command line arguments

argument	description	required?
--directory file	Directory containing segment data. This could be generated by unzipping an "index.zip" from deep storage.	yes
--output file	File where output will be written.	yes
--filter json	JSON-encoded query filter. Omit to include all rows.	no
--column columnName	Column to include. Specify multiple times for multiple columns, or omit to include all columns.	no
--time-iso8601	Dump __time column in ISO8601 format rather than long.	no
--metadata	Dump metadata instead of actual rows, will ignore --filter and --column selections.	no