mirror of https://github.com/apache/druid.git
46 lines
1.0 KiB
Markdown
46 lines
1.0 KiB
Markdown
---
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layout: doc_page
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---
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## Datasources
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A data source is the Druid equivalent of a database table. However, a query can also masquerade as a data source, providing subquery-like functionality. Query data sources are currently supported only by [GroupBy](../querying/groupbyquery.html) queries.
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### Table Data Source
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The table data source is the most common type. It's represented by a string, or by the full structure:
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```json
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{
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"type": "table",
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"name": "<string_value>"
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}
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```
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### Union Data Source
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This data source unions two or more table data sources.
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```json
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{
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"type": "union",
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"dataSources": ["<string_value1>", "<string_value2>", "<string_value3>", ... ]
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}
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```
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Note that the data sources being unioned should have the same schema.
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Union Queries should be always sent to the broker/router node and are *NOT* supported directly by the historical nodes.
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### Query Data Source
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This is used for nested groupBys and is only currently supported for groupBys.
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```json
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{
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"type": "query",
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"query": {
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"type": "groupBy",
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...
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}
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}
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```
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