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Segment Metadata Queries

Segment metadata queries return per segment information about:

• Cardinality of all columns in the segment
• Estimated byte size for the segment columns in TSV format
• Interval the segment covers
• Column type of all the columns in the segment
• Estimated total segment byte size in TSV format
• Segment id

{
  "queryType":"segmentMetadata",
  "dataSource":"sample_datasource",
  "intervals":["2013-01-01/2014-01-01"]
}

There are several main parts to a segment metadata query:

property	description	required?
queryType	This String should always be “segmentMetadata”; this is the first thing Druid looks at to figure out how to interpret the query	yes
dataSource	A String defining the data source to query, very similar to a table in a relational database	yes
intervals	A JSON Object representing ISO-8601 Intervals. This defines the time ranges to run the query over.	yes
toInclude	A JSON Object representing what columns should be included in the result. Defaults to “all”.	no
merge	Merge all individual segment metadata results into a single result	no
context	An additional JSON Object which can be used to specify certain flags.	no

The format of the result is:

[ {
  "id" : "some_id",
  "intervals" : [ "2013-05-13T00:00:00.000Z/2013-05-14T00:00:00.000Z" ],
  "columns" : {
    "__time" : { "type" : "LONG", "size" : 407240380, "cardinality" : null },
    "dim1" : { "type" : "STRING", "size" : 100000, "cardinality" : 1944 },
    "dim2" : { "type" : "STRING", "size" : 100000, "cardinality" : 1504 },
    "metric1" : { "type" : "FLOAT", "size" : 100000, "cardinality" : null }
  },
  "size" : 300000
} ]

toInclude

There are 3 types of toInclude objects.

All

The grammar is as follows:

"toInclude": { "type": "all"}

None

The grammar is as follows:

"toInclude": { "type": "none"}

List

The grammar is as follows:

"toInclude": { "type": "list", "columns": [<string list of column names>]}