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 |
|---|---|
| topnmetricspec | Sorting (topN) |
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.
In Apache Druid, the topN metric spec specifies how topN values should be sorted.
Numeric TopNMetricSpec
The simplest metric specification is a String value indicating the metric to sort topN results by. They are included in a topN query with:
"metric": "<metric_name>"
The metric field can also be given as a JSON object. The grammar for dimension values sorted by numeric value is shown below:
"metric": {
"type": "numeric",
"metric": "<metric_name>"
}
| property | description | required? |
|---|---|---|
| type | this indicates a numeric sort | yes |
| metric | the actual metric field in which results will be sorted by | yes |
Dimension TopNMetricSpec
This metric specification sorts TopN results by dimension value, using one of the sorting orders described here: Sorting Orders
| property | type | description | required? |
|---|---|---|---|
| type | String | this indicates a sort a dimension's values | yes, must be 'dimension' |
| ordering | String | Specifies the sorting order. Can be one of the following values: "lexicographic", "alphanumeric", "numeric", "strlen". See Sorting Orders for more details. | no, default: "lexicographic" |
| previousStop | String | the starting point of the sort. For example, if a previousStop value is 'b', all values before 'b' are discarded. This field can be used to paginate through all the dimension values. | no |
The following metricSpec uses lexicographic sorting.
"metric": {
"type": "dimension",
"ordering": "lexicographic",
"previousStop": "<previousStop_value>"
}
Note that in earlier versions of Druid, the functionality provided by the DimensionTopNMetricSpec was handled by two separate spec types, Lexicographic and Alphanumeric (when only two sorting orders were supported). These spec types have been deprecated but are still usable.
Inverted TopNMetricSpec
Sort dimension values in inverted order, i.e inverts the order of the delegate metric spec. It can be used to sort the values in ascending order.
"metric": {
"type": "inverted",
"metric": <delegate_top_n_metric_spec>
}
| property | description | required? |
|---|---|---|
| type | this indicates an inverted sort | yes |
| metric | the delegate metric spec. | yes |