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65 lines
1.9 KiB
Markdown
65 lines
1.9 KiB
Markdown
---
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id: datasource
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title: "Datasources"
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---
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<!--
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~ Licensed to the Apache Software Foundation (ASF) under one
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~ or more contributor license agreements. See the NOTICE file
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~ distributed with this work for additional information
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~ regarding copyright ownership. The ASF licenses this file
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~ to you under the Apache License, Version 2.0 (the
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~ "License"); you may not use this file except in compliance
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~ with the License. You may obtain a copy of the License at
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~
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~ http://www.apache.org/licenses/LICENSE-2.0
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~
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~ Unless required by applicable law or agreed to in writing,
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~ software distributed under the License is distributed on an
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~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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~ KIND, either express or implied. See the License for the
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~ specific language governing permissions and limitations
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~ under the License.
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-->
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A data source is the Apache Druid (incubating) 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.md) queries.
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### Table datasource
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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 datasource
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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 a Broker/Router process and are *NOT* supported directly by the Historical processes.
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### Query datasource
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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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