clintropolis commented on a change in pull request #11068:
URL: https://github.com/apache/druid/pull/11068#discussion_r608306486
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File path: processing/src/main/java/org/apache/druid/query/Queries.java
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@@ -219,4 +224,73 @@
return retVal;
}
+
+ /**
+ * Helper for implementations of {@link Query#getRequiredColumns()}. Returns
the list of columns that will be read
+ * out of a datasource by a query that uses the provided objects in the
usual way.
+ *
+ * The returned set always contains {@code __time}, no matter what.
+ *
+ * If the virtual columns, filter, dimensions, aggregators, or additional
columns refer to a virtual column, then the
+ * inputs of the virtual column will be returned instead of the name of the
virtual column itself. Therefore, the
+ * returned list will never contain the names of any virtual columns.
+ *
+ * @param virtualColumns virtual columns whose inputs should be included.
+ * @param filter optional filter whose inputs should be included.
+ * @param dimensions dimension specs whose inputs should be included.
+ * @param aggregators aggregators whose inputs should be included.
+ * @param additionalColumns additional columns to include. Each of these
will be added to the returned set, unless it
+ * refers to a virtual column, in which case the
virtual column inputs will be added instead.
+ */
+ public static Set<String> computeRequiredColumns(
Review comment:
:+1:
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