mirror of https://github.com/apache/druid.git
46 lines
1.6 KiB
Markdown
46 lines
1.6 KiB
Markdown
---
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layout: doc_page
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---
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Segment metadata queries return per segment information about:
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* Cardinality of all columns in the segment
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* Estimated byte size for the segment columns in TSV format
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* Interval the segment covers
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* Column type of all the columns in the segment
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* Estimated total segment byte size in TSV format
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* Segment id
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```json
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{
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"queryType":"segmentMetadata",
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"dataSource":"sample_datasource",
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"intervals":["2013-01-01/2014-01-01"],
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}
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```
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There are several main parts to a segment metadata query:
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|property|description|required?|
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|--------|-----------|---------|
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|queryType|This String should always be "segmentMetadata"; this is the first thing Druid looks at to figure out how to interpret the query|yes|
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|dataSource|A String defining the data source to query, very similar to a table in a relational database|yes|
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|intervals|A JSON Object representing ISO-8601 Intervals. This defines the time ranges to run the query over.|yes|
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|merge|Merge all individual segment metadata results into a single result|no|
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|context|An additional JSON Object which can be used to specify certain flags.|no|
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The format of the result is:
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```json
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[ {
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"id" : "some_id",
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"intervals" : [ "2013-05-13T00:00:00.000Z/2013-05-14T00:00:00.000Z" ],
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"columns" : {
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"__time" : { "type" : "LONG", "size" : 407240380, "cardinality" : null },
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"dim1" : { "type" : "STRING", "size" : 100000, "cardinality" : 1944 },
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"dim2" : { "type" : "STRING", "size" : 100000, "cardinality" : 1504 },
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"metric1" : { "type" : "FLOAT", "size" : 100000, "cardinality" : null }
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},
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"size" : 300000
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} ]
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```
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