fix bug with CastOperatorConversion with types which cannot be mapped to native druid types (#17011)

processing/src/main/java/org/apache/druid/math/expr/ExpressionTypeConversion.java

@@ -91,10 +91,7 @@ public class ExpressionTypeConversion
       return type;
     }
     if (type.isArray() || other.isArray()) {
-      if (!Objects.equals(type, other)) {
+      return leastRestrictiveType(type, other);
-        throw new Types.IncompatibleTypeException(type, other);
-      }
-      return type;
     }
     if (type.is(ExprType.COMPLEX) || other.is(ExprType.COMPLEX)) {
       if (type.getComplexTypeName() == null) {
@@ -134,12 +131,8 @@ public class ExpressionTypeConversion
     if (other == null) {
       return type;
     }
-    // arrays cannot be auto converted
     if (type.isArray() || other.isArray()) {
-      if (!Objects.equals(type, other)) {
+      return leastRestrictiveType(type, other);
-        throw new Types.IncompatibleTypeException(type, other);
-      }
-      return type;
     }
     if (type.is(ExprType.COMPLEX) || other.is(ExprType.COMPLEX)) {
       if (type.getComplexTypeName() == null) {

processing/src/test/java/org/apache/druid/math/expr/OutputTypeTest.java

@@ -20,13 +20,10 @@
 package org.apache.druid.math.expr;
 
 import com.google.common.collect.ImmutableMap;
-import org.apache.druid.java.util.common.IAE;
 import org.apache.druid.segment.column.ColumnType;
 import org.apache.druid.testing.InitializedNullHandlingTest;
 import org.junit.Assert;
-import org.junit.Rule;
 import org.junit.Test;
-import org.junit.rules.ExpectedException;
 
 import java.util.Map;
 
@@ -48,9 +45,6 @@ public class OutputTypeTest extends InitializedNullHandlingTest
                   .build()
   );
 
-  @Rule
-  public ExpectedException expectedException = ExpectedException.none();
-
   @Test
   public void testConstantsAndIdentifiers()
   {
@@ -541,7 +535,6 @@ public class OutputTypeTest extends InitializedNullHandlingTest
         ExpressionType.DOUBLE,
         ExpressionTypeConversion.operator(ExpressionType.LONG, ExpressionType.STRING)
     );
-    // unless it is an array, and those have to be the same
     Assert.assertEquals(
         ExpressionType.LONG_ARRAY,
         ExpressionTypeConversion.operator(ExpressionType.LONG_ARRAY, ExpressionType.LONG_ARRAY)
@@ -554,7 +547,30 @@ public class OutputTypeTest extends InitializedNullHandlingTest
         ExpressionType.STRING_ARRAY,
         ExpressionTypeConversion.operator(ExpressionType.STRING_ARRAY, ExpressionType.STRING_ARRAY)
     );
-
+    Assert.assertEquals(
+        ExpressionType.LONG_ARRAY,
+        ExpressionTypeConversion.operator(ExpressionType.LONG_ARRAY, ExpressionType.LONG)
+    );
+    Assert.assertEquals(
+        ExpressionType.STRING_ARRAY,
+        ExpressionTypeConversion.operator(ExpressionType.STRING, ExpressionType.LONG_ARRAY)
+    );
+    Assert.assertEquals(
+        ExpressionType.DOUBLE_ARRAY,
+        ExpressionTypeConversion.operator(ExpressionType.LONG_ARRAY, ExpressionType.DOUBLE_ARRAY)
+    );
+    Assert.assertEquals(
+        ExpressionType.DOUBLE_ARRAY,
+        ExpressionTypeConversion.operator(ExpressionType.LONG, ExpressionType.DOUBLE_ARRAY)
+    );
+    Assert.assertEquals(
+        ExpressionType.STRING_ARRAY,
+        ExpressionTypeConversion.operator(ExpressionType.LONG_ARRAY, ExpressionType.STRING_ARRAY)
+    );
+    Assert.assertEquals(
+        ExpressionType.STRING_ARRAY,
+        ExpressionTypeConversion.operator(ExpressionType.STRING_ARRAY, ExpressionType.DOUBLE_ARRAY)
+    );
     ExpressionType nested = ExpressionType.fromColumnType(ColumnType.NESTED_DATA);
     Assert.assertEquals(
         nested,
@@ -619,7 +635,6 @@ public class OutputTypeTest extends InitializedNullHandlingTest
         ExpressionType.STRING,
         ExpressionTypeConversion.function(ExpressionType.STRING, ExpressionType.STRING)
     );
-    // unless it is an array, and those have to be the same
     Assert.assertEquals(
         ExpressionType.LONG_ARRAY,
         ExpressionTypeConversion.function(ExpressionType.LONG_ARRAY, ExpressionType.LONG_ARRAY)
@@ -632,6 +647,30 @@ public class OutputTypeTest extends InitializedNullHandlingTest
         ExpressionType.STRING_ARRAY,
         ExpressionTypeConversion.function(ExpressionType.STRING_ARRAY, ExpressionType.STRING_ARRAY)
     );
+    Assert.assertEquals(
+        ExpressionType.DOUBLE_ARRAY,
+        ExpressionTypeConversion.function(ExpressionType.DOUBLE_ARRAY, ExpressionType.LONG_ARRAY)
+    );
+    Assert.assertEquals(
+        ExpressionType.STRING_ARRAY,
+        ExpressionTypeConversion.function(ExpressionType.DOUBLE_ARRAY, ExpressionType.STRING_ARRAY)
+    );
+    Assert.assertEquals(
+        ExpressionType.STRING_ARRAY,
+        ExpressionTypeConversion.function(ExpressionType.STRING_ARRAY, ExpressionType.LONG_ARRAY)
+    );
+    Assert.assertEquals(
+        ExpressionType.STRING_ARRAY,
+        ExpressionTypeConversion.function(ExpressionType.STRING, ExpressionType.LONG_ARRAY)
+    );
+    Assert.assertEquals(
+        ExpressionType.DOUBLE_ARRAY,
+        ExpressionTypeConversion.function(ExpressionType.LONG_ARRAY, ExpressionType.DOUBLE_ARRAY)
+    );
+    Assert.assertEquals(
+        ExpressionType.DOUBLE_ARRAY,
+        ExpressionTypeConversion.function(ExpressionType.LONG, ExpressionType.DOUBLE_ARRAY)
+    );
     ExpressionType nested = ExpressionType.fromColumnType(ColumnType.NESTED_DATA);
     Assert.assertEquals(
         nested,
@@ -719,27 +758,6 @@ public class OutputTypeTest extends InitializedNullHandlingTest
     );
   }
 
-  @Test
-  public void testAutoConversionArrayMismatchArrays()
-  {
-    expectedException.expect(IAE.class);
-    ExpressionTypeConversion.function(ExpressionType.DOUBLE_ARRAY, ExpressionType.LONG_ARRAY);
-  }
-
-  @Test
-  public void testAutoConversionArrayMismatchArrayScalar()
-  {
-    expectedException.expect(IAE.class);
-    ExpressionTypeConversion.function(ExpressionType.DOUBLE_ARRAY, ExpressionType.LONG);
-  }
-
-  @Test
-  public void testAutoConversionArrayMismatchScalarArray()
-  {
-    expectedException.expect(IAE.class);
-    ExpressionTypeConversion.function(ExpressionType.DOUBLE, ExpressionType.LONG_ARRAY);
-  }
-
   private void assertOutputType(String expression, Expr.InputBindingInspector inspector, ExpressionType outputType)
   {
     final Expr expr = Parser.parse(expression, ExprMacroTable.nil(), false);

sql/src/main/java/org/apache/druid/sql/calcite/expression/builtin/CastOperatorConversion.java

@@ -93,11 +93,17 @@ public class CastOperatorConversion implements SqlOperatorConversion
                                               : ExpressionType.fromColumnType(toDruidType);
 
       if (toExpressionType == null) {
-        // We have no runtime type for these SQL types.
+        // We have no runtime type for to SQL type.
         return null;
       }
       if (fromExpressionType == null) {
-        return DruidExpression.ofLiteral(toDruidType, DruidExpression.nullLiteral());
+        // Calcites.getColumnTypeForRelDataType returns null in cases of NULL, but also any type which cannot be
+        // mapped to a native druid type. in the case of the former, make a null literal of the toType
+        if (fromType.equals(SqlTypeName.NULL)) {
+          return DruidExpression.ofLiteral(toDruidType, DruidExpression.nullLiteral());
+        }
+        // otherwise, we have no runtime type for from SQL type.
+        return null;
       }
 
       final DruidExpression typeCastExpression;

sql/src/main/java/org/apache/druid/sql/calcite/planner/Calcites.java

@@ -218,6 +218,9 @@ public class Calcites
       if (elementType != null) {
         return ColumnType.ofArray(elementType);
       }
+      if (type.getComponentType().getSqlTypeName() == SqlTypeName.NULL) {
+        return ColumnType.LONG_ARRAY;
+      }
       return null;
     } else {
       return null;

sql/src/test/java/org/apache/druid/sql/calcite/CalciteArraysQueryTest.java

@@ -116,8 +116,6 @@ public class CalciteArraysQueryTest extends BaseCalciteQueryTest
     }
   }
 
-  // test some query stuffs, sort of limited since no native array column types so either need to use constructor or
-  // array aggregator
   @Test
   public void testSelectConstantArrayExpressionFromTable()
   {
@@ -7478,4 +7476,26 @@ public class CalciteArraysQueryTest extends BaseCalciteQueryTest
         )
     );
   }
+
+  @Test
+  public void testNullArray()
+  {
+    testQuery(
+        "SELECT arrayLongNulls = ARRAY[null, null] FROM druid.arrays LIMIT 1",
+        ImmutableList.of(
+            newScanQueryBuilder()
+                .dataSource(CalciteTests.ARRAYS_DATASOURCE)
+                .intervals(querySegmentSpec(Filtration.eternity()))
+                .virtualColumns(expressionVirtualColumn("v0", "(\"arrayLongNulls\" == array(null,null))", ColumnType.LONG))
+                .columns("v0")
+                .resultFormat(ScanQuery.ResultFormat.RESULT_FORMAT_COMPACTED_LIST)
+                .limit(1)
+                .context(QUERY_CONTEXT_DEFAULT)
+                .build()
+        ),
+        ImmutableList.of(
+            new Object[]{false}
+        )
+    );
+  }
 }