mirror of https://github.com/apache/druid.git
58 lines
2.3 KiB
Markdown
58 lines
2.3 KiB
Markdown
---
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id: limitspec
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title: "Sorting and limiting (groupBy)"
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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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> Apache Druid supports two query languages: [Druid SQL](sql.md) and [native queries](querying.md).
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> This document describes the native
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> language. For information about sorting in SQL, refer to the [SQL documentation](sql.md#order-by).
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The limitSpec field provides the functionality to sort and limit the set of results from a groupBy query. If you group by a single dimension and are ordering by a single metric, we highly recommend using [TopN Queries](../querying/topnquery.md) instead. The performance will be substantially better. Available options are:
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### DefaultLimitSpec
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The default limit spec takes a limit and the list of columns to do an orderBy operation over. The grammar is:
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```json
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{
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"type" : "default",
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"limit" : <integer_value>,
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"columns" : [list of OrderByColumnSpec],
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}
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```
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#### OrderByColumnSpec
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OrderByColumnSpecs indicate how to do order by operations. Each order-by condition can be a `jsonString` or a map of the following form:
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```json
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{
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"dimension" : "<Any dimension or metric name>",
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"direction" : <"ascending"|"descending">,
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"dimensionOrder" : <"lexicographic"(default)|"alphanumeric"|"strlen"|"numeric">
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}
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```
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If only the dimension is provided (as a JSON string), the default order-by is ascending with lexicographic sorting.
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See [Sorting Orders](./sorting-orders.md) for more information on the sorting orders specified by "dimensionOrder".
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