SQL: Support for descending timeseries. (#3790)

sql/src/main/java/io/druid/sql/calcite/rel/DruidQueryBuilder.java

@@ -269,8 +269,7 @@ public class DruidQueryBuilder
           limitSpec == null || limitSpec.getColumns().isEmpty()
           || (limitSpec.getLimit() == Integer.MAX_VALUE
               && limitSpec.getColumns().size() == 1
-              && limitSpec.getColumns().get(0).getDimension().equals(dimensionSpec.getOutputName())
-              && limitSpec.getColumns().get(0).getDirection() == OrderByColumnSpec.Direction.ASCENDING);
+              && limitSpec.getColumns().get(0).getDimension().equals(dimensionSpec.getOutputName()));
 
       if (sortingOnTime) {
         return ExtractionFns.toQueryGranularity(dimensionSpec.getExtractionFn());

sql/src/main/java/io/druid/sql/calcite/rel/QueryMaker.java

@@ -38,6 +38,7 @@ import io.druid.query.Result;
 import io.druid.query.dimension.DimensionSpec;
 import io.druid.query.groupby.GroupByQuery;
 import io.druid.query.groupby.having.DimFilterHavingSpec;
+import io.druid.query.groupby.orderby.DefaultLimitSpec;
 import io.druid.query.groupby.orderby.OrderByColumnSpec;
 import io.druid.query.select.EventHolder;
 import io.druid.query.select.PagingSpec;
@@ -217,13 +218,26 @@ public class QueryMaker
     final Row.RowBuilder rowBuilder = Row.newBuilder(fieldList.size());
     final Filtration filtration = Filtration.create(queryBuilder.getFilter()).optimize(druidTable);
 
+    final boolean descending;
+
+    if (queryBuilder.getLimitSpec() != null) {
+      final DefaultLimitSpec limitSpec = queryBuilder.getLimitSpec();
+
+      // Sanity checks; these preconditions should be assured by DruidQueryBuilder.accumulate.
+      Preconditions.checkState(limitSpec.getColumns().size() == 1);
+      Preconditions.checkState(limitSpec.getColumns().get(0).getDimension().equals(timeOutputName));
+      descending = limitSpec.getColumns().get(0).getDirection() == OrderByColumnSpec.Direction.DESCENDING;
+    } else {
+      descending = false;
+    }
+
     final Map<String, Object> context = Maps.newHashMap();
     context.put("skipEmptyBuckets", true);
 
     final TimeseriesQuery query = new TimeseriesQuery(
         druidTable.getDataSource(),
         filtration.getQuerySegmentSpec(),
-        false,
+        descending,
         filtration.getDimFilter(),
         queryGranularity,
         queryBuilder.getGrouping().getAggregatorFactories(),

sql/src/test/java/io/druid/sql/calcite/CalciteQueryTest.java

@@ -1950,7 +1950,12 @@ public class CalciteQueryTest
   public void testTimeseries() throws Exception
   {
     testQuery(
-        "SELECT gran, SUM(cnt) FROM (SELECT floor(__time TO month) AS gran, cnt FROM druid.foo) AS x GROUP BY gran ORDER BY gran",
+        "SELECT gran, SUM(cnt) FROM (\n"
+        + "  SELECT floor(__time TO month) AS gran,\n"
+        + "  cnt FROM druid.foo\n"
+        + ") AS x\n"
+        + "GROUP BY gran\n"
+        + "ORDER BY gran",
         ImmutableList.<Query>of(
             Druids.newTimeseriesQueryBuilder()
                   .dataSource(CalciteTests.DATASOURCE)
@@ -1967,6 +1972,33 @@ public class CalciteQueryTest
     );
   }
 
+  @Test
+  public void testTimeseriesDescending() throws Exception
+  {
+    testQuery(
+        "SELECT gran, SUM(cnt) FROM (\n"
+        + "  SELECT floor(__time TO month) AS gran,\n"
+        + "  cnt FROM druid.foo\n"
+        + ") AS x\n"
+        + "GROUP BY gran\n"
+        + "ORDER BY gran DESC",
+        ImmutableList.<Query>of(
+            Druids.newTimeseriesQueryBuilder()
+                  .dataSource(CalciteTests.DATASOURCE)
+                  .intervals(QSS(Filtration.eternity()))
+                  .granularity(QueryGranularities.MONTH)
+                  .aggregators(AGGS(new LongSumAggregatorFactory("a0", "cnt")))
+                  .descending(true)
+                  .context(TIMESERIES_CONTEXT)
+                  .build()
+        ),
+        ImmutableList.of(
+            new Object[]{T("2001-01-01"), 3L},
+            new Object[]{T("2000-01-01"), 3L}
+        )
+    );
+  }
+
   @Test
   public void testGroupByExtractYear() throws Exception
   {