Adding support of MAP_REMOVE_NULL_VALUES for Presto

presto-docs/src/main/sphinx/functions/map.rst

@@ -98,6 +98,10 @@ Map Functions
 
         SELECT map_top_n_keys(map(ARRAY['a', 'b', 'c'], ARRAY[1, 2, 3]), 2, (x, y) -> IF(x < y, -1, IF(x = y, 0, 1))) --- ['c', 'b']
 
+.. function:: map_remove_null_values(x(K,V)) -> map(K, V)
+
+    Removes all the entries where the value is null from the map ``x``.
+
 .. function:: map_normalize(x(varchar,double)) -> map(varchar,double)
 
     Returns the map with the same keys but all non-null values are scaled proportionally so that the sum of values becomes 1.

presto-main/src/main/java/com/facebook/presto/operator/scalar/sql/MapSqlFunctions.java

@@ -67,4 +67,15 @@ public static String mapTopNValuesComparator()
     {
         return "RETURN IF(n < 0, fail('n must be greater than or equal to 0'), slice(reverse(array_sort(remove_nulls(map_values(input)), f)) || filter(map_values(input), x -> x is null), 1, n))";
     }
+
+    @SqlInvokedScalarFunction(value = "map_remove_null_values", deterministic = true, calledOnNullInput = true)
+    @Description("Constructs a map by removing all the keys with null values.")
+    @TypeParameter("K")
+    @TypeParameter("V")
+    @SqlParameter(name = "input", type = "map(K, V)")
+    @SqlType("map(K, V)")
+    public static String mapRemoveNulls()
+    {
+        return "RETURN map_filter(input, (k, v) -> v is not null)";
+    }
 }

presto-main/src/test/java/com/facebook/presto/operator/scalar/sql/TestMapRemoveNullValuesFunction.java

@@ -0,0 +1,65 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.facebook.presto.operator.scalar.sql;
+
+import com.facebook.presto.common.type.ArrayType;
+import com.facebook.presto.operator.scalar.AbstractTestFunctions;
+import com.google.common.collect.ImmutableMap;
+import org.testng.annotations.Test;
+
+import static com.facebook.presto.common.type.DecimalType.createDecimalType;
+import static com.facebook.presto.common.type.IntegerType.INTEGER;
+import static com.facebook.presto.common.type.UnknownType.UNKNOWN;
+import static com.facebook.presto.common.type.VarcharType.createVarcharType;
+import static com.facebook.presto.util.StructuralTestUtil.mapType;
+import static java.util.Collections.emptyList;
+import static java.util.Collections.emptyMap;
+import static java.util.Collections.singletonList;
+
+public class TestMapRemoveNullValuesFunction
+        extends AbstractTestFunctions
+{
+    @Test
+    public void test()
+    {
+        assertFunction(
+                "MAP_REMOVE_NULL_VALUES(MAP(ARRAY[1, 2, 3], ARRAY[4, 5, 6]))",
+                mapType(INTEGER, INTEGER),
+                ImmutableMap.of(1, 4, 2, 5, 3, 6));
+        assertFunction(
+                "MAP_REMOVE_NULL_VALUES(MAP(ARRAY[-1, -2, -3], ARRAY[null, 5.0, null]))",
+                mapType(INTEGER, createDecimalType(2, 1)),
+                ImmutableMap.of(-2, decimal("5.0")));
+        assertFunction(
+                "MAP_REMOVE_NULL_VALUES(MAP(ARRAY['ab', 'bc', 'cd'], ARRAY[null, null, null]))",
+                mapType(createVarcharType(2), UNKNOWN),
+                emptyMap());
+        assertFunction(
+                "MAP_REMOVE_NULL_VALUES(MAP(ARRAY[123.0, 99.5, 1000.99], ARRAY['x', 'y', 'z']))",
+                mapType(createDecimalType(6, 2), createVarcharType(1)),
+                ImmutableMap.of(decimal("123.00"), "x", decimal("99.50"), "y", decimal("1000.99"), "z"));
+        assertFunction(
+                "MAP_REMOVE_NULL_VALUES(MAP(ARRAY['a', 'b', 'c'], ARRAY[ARRAY[1], ARRAY[], ARRAY[null]]))",
+                mapType(createVarcharType(1), new ArrayType(INTEGER)),
+                ImmutableMap.of("a", singletonList(1), "b", emptyList(), "c", singletonList(null)));
+        assertFunction(
+                "MAP_REMOVE_NULL_VALUES(MAP(ARRAY[], ARRAY[]))",
+                mapType(UNKNOWN, UNKNOWN),
+                emptyMap());
+        assertFunction(
+                "MAP_REMOVE_NULL_VALUES(null)",
+                mapType(UNKNOWN, UNKNOWN),
+                null);
+    }
+}