42590ae64b
* 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.
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| id | title |
|---|---|
| limitspec | Sorting and limiting (groupBy) |
Apache Druid supports two query languages: Druid SQL and native queries. This document describes the native language. For information about sorting in SQL, refer to the SQL documentation.
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 instead. The performance will be substantially better. Available options are:
DefaultLimitSpec
The default limit spec takes a limit and the list of columns to do an orderBy operation over. The grammar is:
{
"type" : "default",
"limit" : <integer_value>,
"columns" : [list of OrderByColumnSpec],
}
OrderByColumnSpec
OrderByColumnSpecs indicate how to do order by operations. Each order-by condition can be a jsonString or a map of the following form:
{
"dimension" : "<Any dimension or metric name>",
"direction" : <"ascending"|"descending">,
"dimensionOrder" : <"lexicographic"(default)|"alphanumeric"|"strlen"|"numeric">
}
If only the dimension is provided (as a JSON string), the default order-by is ascending with lexicographic sorting.
See Sorting Orders for more information on the sorting orders specified by "dimensionOrder".