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https://issues.apache.org/jira/browse/CALCITE-1276?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde updated CALCITE-1276:
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Component/s: druid
> In Druid adapter, deduce columns by running a "segmentMetadata" query
> ---------------------------------------------------------------------
>
> Key: CALCITE-1276
> URL: https://issues.apache.org/jira/browse/CALCITE-1276
> Project: Calcite
> Issue Type: Bug
> Components: druid
> Reporter: Julian Hyde
> Assignee: Julian Hyde
>
> In Druid adapter, deduce columns by running a "segmentMetadata" query.
> Currently a Druid model must contain "dimensions" and "metrics" fields. If
> either of these are absent, Calcite should run a [segment metadata
> query|http://druid.io/docs/latest/querying/segmentmetadataquery.html] and
> take the resulting "columns" and "aggregators" fields and make them into
> columns.
> The effect will be that the Druid adapter will be easier to configure. You
> will be able to connect without a model, per CALCITE-1259:
> {code}
> jdbc:calcite:schema=wiki; schemaFactory=
> org.apache.calcite.adapter.druid.DruidSchemaFactory;
> schema.url=http://localhost:8082/druid/v2/?pretty
> {code}
> It will also adapt to schema changes. If there are multiple segments, and the
> schema evolves over time, I suppose that the segments might have different
> columns and aggregators. Calcite should use {{"merge": true,
> "lenientAggregatorMerge": false}} to combine them.
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