Improve Druid documentation
Project: http://git-wip-us.apache.org/repos/asf/calcite/repo Commit: http://git-wip-us.apache.org/repos/asf/calcite/commit/56b753df Tree: http://git-wip-us.apache.org/repos/asf/calcite/tree/56b753df Diff: http://git-wip-us.apache.org/repos/asf/calcite/diff/56b753df Branch: refs/heads/master Commit: 56b753df4a2e6b971720333e0fc2bef4719d50ac Parents: 0c58243 Author: Julian Hyde <[email protected]> Authored: Fri Jun 10 16:56:49 2016 -0700 Committer: Julian Hyde <[email protected]> Committed: Mon Jun 13 00:29:21 2016 -0700 ---------------------------------------------------------------------- site/_docs/druid_adapter.md | 102 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 101 insertions(+), 1 deletion(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/calcite/blob/56b753df/site/_docs/druid_adapter.md ---------------------------------------------------------------------- diff --git a/site/_docs/druid_adapter.md b/site/_docs/druid_adapter.md index 9de2fb9..d45caba 100644 --- a/site/_docs/druid_adapter.md +++ b/site/_docs/druid_adapter.md @@ -140,7 +140,7 @@ sqlline> {% endhighlight %} That query shows the top 5 countries of origin of wiki page edits -on 2015-09-12 (the date covered by the wikiticker data set). +on 2015-09-12 (the date covered by the `wikiticker` data set). Now let's see how the query was evaluated: @@ -173,3 +173,103 @@ into a single Druid data set called "foodmart". You can access it via the `druid/src/test/resources/druid-foodmart-model.json` model. + +# Simplifying the model + +If less metadata is provided in the model, the Druid adapter can discover +it automatically from Druid. Here is a schema equivalent to the previous one +but with `dimensions`, `metrics` and `timestampColumn` removed: + +{% highlight json %} +{ + "version": "1.0", + "defaultSchema": "wiki", + "schemas": [ + { + "type": "custom", + "name": "wiki", + "factory": "org.apache.calcite.adapter.druid.DruidSchemaFactory", + "operand": { + "url": "http://localhost:8082";, + "coordinatorUrl": "http://localhost:8081"; + }, + "tables": [ + { + "name": "wiki", + "factory": "org.apache.calcite.adapter.druid.DruidTableFactory", + "operand": { + "dataSource": "wikiticker", + "interval": "1900-01-09T00:00:00.000Z/2992-01-10T00:00:00.000Z" + } + } + ] + } + ] +} +{% endhighlight %} + +Calcite dispatches a +[segmentMetadataQuery](http://druid.io/docs/latest/querying/segmentmetadataquery.html) +to Druid to discover the columns of the table. +Now, let's take out the `tables` element: + +{% highlight json %} +{ + "version": "1.0", + "defaultSchema": "wiki", + "schemas": [ + { + "type": "custom", + "name": "wiki", + "factory": "org.apache.calcite.adapter.druid.DruidSchemaFactory", + "operand": { + "url": "http://localhost:8082";, + "coordinatorUrl": "http://localhost:8081"; + } + } + ] +} +{% endhighlight %} + +Calcite discovers the "wikiticker" data source via the +[/druid/coordinator/v1/metadata/datasources](http://druid.io/docs/latest/design/coordinator.html#metadata-store-information) +REST call. Now that the "wiki" table element is removed, the table is called +"wikiticker". Any other data sources present in Druid will also appear as +tables. + +Our model is now a single schema based on a custom schema factory with only two +operands, so we can +[dispense with the model](https://issues.apache.org/jira/browse/CALCITE-1206) +and supply the operands as part of the connect string: + +{% highlight bash %} + jdbc:calcite:schemaFactory=org.apache.calcite.adapter.druid.DruidSchemaFactory; schema.url=http://localhost:8082; schema.coordinatorUrl=http://localhost:8081 +{% endhighlight %} + +In fact, those are the +[default values of the operands]({{ site.apiRoot }}/org/apache/calcite/adapter/druid/DruidSchemaFactory.html), +so we can omit them: + +{% highlight bash %} + jdbc:calcite:schemaFactory=org.apache.calcite.adapter.druid.DruidSchemaFactory +{% endhighlight %} + +Now, we can connect to `sqlline` using a very simple connect string, and list +the available tables: + +{% highlight bash %} +$ ./sqlline +sqlline> !connect jdbc:calcite:schemaFactory=org.apache.calcite.adapter.druid.DruidSchemaFactory admin admin +sqlline> !tables ++-----------+-------------+------------+--------------+ +| TABLE_CAT | TABLE_SCHEM | TABLE_NAME | TABLE_TYPE | ++-----------+-------------+------------+--------------+ +| | adhoc | foodmart | TABLE | +| | adhoc | wikiticker | TABLE | +| | metadata | COLUMNS | SYSTEM_TABLE | +| | metadata | TABLES | SYSTEM_TABLE | ++-----------+-------------+------------+--------------+ +{% endhighlight %} + +We see the two system tables (`TABLES` and `COLUMNS`), +and the two tables in Druid (`foodmart` and `wikiticker`).
