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573aa96bd6
Fixes #1727. revert to doing merging for results for union queries on broker. revert unrelated changes Add test for union query runner Add test remove unused imports fix imports fix renamed file fix test update docs.
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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