Add schema check for overlap between dimension and metric names

docs/content/Ingestion.md

@@ -184,3 +184,12 @@ Batch Ingestion: See [Batch ingestion](Batch-ingestion.html)
 
 Real-time Ingestion: See [Real-time ingestion](Realtime-ingestion.html).
 Batch Ingestion: See [Batch ingestion](Batch-ingestion.html)
+
+# Evaluating Timestamp, Dimensions and Metrics
+
+Druid will interpret dimensions, dimension exclusions, and metrics in the following order:
+
+* Any column listed in the list of dimensions is treated as a dimension.
+* Any column listed in the list of dimension exclusions is excluded as a dimension.
+* The timestamp column and columns/fieldNames required by metrics are excluded by default.
+* If a metric is also listed as a dimension, the metric must have a different name than the dimension name.

server/src/main/java/io/druid/segment/indexing/DataSchema.java

@@ -20,7 +20,9 @@ package io.druid.segment.indexing;
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.google.api.client.repackaged.com.google.common.base.Preconditions;
+import com.google.common.collect.Iterables;
 import com.google.common.collect.Sets;
+import com.metamx.common.IAE;
 import com.metamx.common.logger.Logger;
 import io.druid.data.input.impl.DimensionsSpec;
 import io.druid.data.input.impl.InputRowParser;
@@ -70,15 +72,25 @@ public class DataSchema
         }
       }
       if (dimensionsSpec != null) {
+        final Set<String> metSet = Sets.newHashSet();
+        for (AggregatorFactory aggregator : aggregators) {
+          metSet.add(aggregator.getName());
+        }
+        final Set<String> dimSet = Sets.newHashSet(dimensionsSpec.getDimensions());
+        final Set<String> overlap = Sets.intersection(metSet, dimSet);
+        if (!overlap.isEmpty()) {
+          throw new IAE(
+              "Cannot have overlapping dimensions and metrics of the same name. Please change the name of the metric. Overlap: %s",
+              overlap
+          );
+        }
+
         this.parser = parser.withParseSpec(
             parser.getParseSpec()
                   .withDimensionsSpec(
                       dimensionsSpec
                           .withDimensionExclusions(
-                              Sets.difference(
-                                  dimensionExclusions,
-                                  Sets.newHashSet(dimensionsSpec.getDimensions())
-                              )
+                              Sets.difference(dimensionExclusions, dimSet)
                           )
                   )
         );

server/src/test/java/io/druid/segment/indexing/DataSchemaTest.java

@@ -19,6 +19,7 @@ package io.druid.segment.indexing;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
+import com.metamx.common.IAE;
 import io.druid.data.input.impl.DimensionsSpec;
 import io.druid.data.input.impl.JSONParseSpec;
 import io.druid.data.input.impl.StringInputRowParser;
@@ -80,4 +81,23 @@ public class DataSchemaTest
         schema.getParser().getParseSpec().getDimensionsSpec().getDimensionExclusions()
     );
   }
+
+  @Test(expected = IAE.class)
+  public void testOverlapMetricNameAndDim() throws Exception
+  {
+    DataSchema schema = new DataSchema(
+        "test",
+        new StringInputRowParser(
+            new JSONParseSpec(
+                new TimestampSpec("time", "auto", null),
+                new DimensionsSpec(ImmutableList.of("time", "dimA", "dimB", "metric1"), ImmutableList.of("dimC"), null)
+            )
+        ),
+        new AggregatorFactory[]{
+            new DoubleSumAggregatorFactory("metric1", "col1"),
+            new DoubleSumAggregatorFactory("metric2", "col2"),
+        },
+        new ArbitraryGranularitySpec(QueryGranularity.DAY, ImmutableList.of(Interval.parse("2014/2015")))
+    );
+  }
 }