[calcite] 03/04: [CALCITE-2946] RelBuilder wrongly skips creation of Aggregate that prunes columns if input produces one row at most

[jc...@apache.org]

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jcamacho pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/calcite.git

commit 2fa7fd79b7dbb09276574784baa80b99edf37412
Author: Jesus Camacho Rodriguez <jc...@apache.org>
AuthorDate: Fri Mar 22 18:31:31 2019 -0700

    [CALCITE-2946] RelBuilder wrongly skips creation of Aggregate that prunes columns if input produces one row at most
    
    Close apache/calcite#1128
---
 .../java/org/apache/calcite/tools/RelBuilder.java     |  2 +-
 .../java/org/apache/calcite/test/RelBuilderTest.java  | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/org/apache/calcite/tools/RelBuilder.java b/core/src/main/java/org/apache/calcite/tools/RelBuilder.java
index c62c42c..7f85432 100644
--- a/core/src/main/java/org/apache/calcite/tools/RelBuilder.java
+++ b/core/src/main/java/org/apache/calcite/tools/RelBuilder.java
@@ -1431,7 +1431,7 @@ public class RelBuilder {
       final Double maxRowCount = mq.getMaxRowCount(peek());
       if (maxRowCount != null && maxRowCount <= 1D) {
         // If there is at most one row, rel is already unique.
-        return this;
+        return project(fields(groupSet.asList()));
       }
     }
     final ImmutableList<ImmutableBitSet> groupSets;
diff --git a/core/src/test/java/org/apache/calcite/test/RelBuilderTest.java b/core/src/test/java/org/apache/calcite/test/RelBuilderTest.java
index 1a50e95..3ec2859 100644
--- a/core/src/test/java/org/apache/calcite/test/RelBuilderTest.java
+++ b/core/src/test/java/org/apache/calcite/test/RelBuilderTest.java
@@ -855,6 +855,25 @@ public class RelBuilderTest {
     assertThat(root, hasTree(expected));
   }
 
+  /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-2946">[CALCITE-2946]
+   * RelBuilder wrongly skips creation of Aggregate that prunes columns if input
+   * produces one row at most</a>. */
+  @Test public void testAggregate5() {
+    final RelBuilder builder = RelBuilder.create(config().build());
+    RelNode root =
+        builder.scan("EMP")
+            .aggregate(builder.groupKey(), builder.count().as("C"))
+            .project(builder.literal(4), builder.literal(2), builder.field(0))
+            .aggregate(builder.groupKey(builder.field(0), builder.field(1)))
+            .build();
+    final String expected = ""
+        + "LogicalProject($f0=[4], $f1=[2])\n"
+        + "  LogicalAggregate(group=[{}], C=[COUNT()])\n"
+        + "    LogicalTableScan(table=[[scott, EMP]])\n";
+    assertThat(root, hasTree(expected));
+  }
+
   @Test public void testAggregateFilter() {
     // Equivalent SQL:
     //   SELECT deptno, COUNT(*) FILTER (WHERE empno > 100) AS c