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* Refresh query docs. Larger changes: - New doc: querying/datasource.md describes the various kinds of datasources you can use, and has examples for both SQL and native. - New doc: querying/query-execution.md describes how native queries are executed at a high level. It doesn't go into the details of specific query engines or how queries run at a per-segment level. But I think it would be good to add or link that content here in the future. - Refreshed doc: querying/sql.md updated to refer to joins, reformatted a bit, added a new "Query translation" section that explains how queries are translated from SQL to native, and removed configuration details (moved to configuration/index.md). - Refreshed doc: querying/joins.md updated to refer to join datasources. Smaller changes: - Add helpful banners to the top of query documentation pages telling people whether a given page describes SQL, native, or both. - Add SQL metrics to operations/metrics.md. - Add some color and cross-links in various places. - Add native query component docs to the sidebar, and renamed them so they look nicer. - Remove Select query from the sidebar. - Fix Broker SQL configs in configuration/index.md. Remove them from querying/sql.md. - Combined querying/searchquery.md and querying/searchqueryspec.md. * Updates. * Fix numbering. * Fix glitches. * Add new words to spellcheck file. * Assorted changes. * Further adjustments. * Add missing punctuation.
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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<!--
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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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> 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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