Adding support of map_top_n_values to Presto

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

@@ -107,6 +107,23 @@ Map Functions
 
     Returns all the values in the map ``x``.
 
+.. function:: map_top_n_values(x(K,V), n) -> array(K)
+
+    Returns top n values in the map ``x``.
+    ``n`` must be a positive integer
+    For bottom ``n`` values, use the function with lambda operator to perform custom sorting
+
+        SELECT map_top_n_values(map(ARRAY['a', 'b', 'c'], ARRAY[1, 2, 3]), 2) --- [3, 2]
+
+.. function:: map_top_n_values(x(K,V), n, function(V,V,int)) -> array(V)
+
+    Returns top n values in the map ``x`` based on the given comparator ``function``. The comparator will take
+    two nullable arguments representing two values of the ``map``. It returns -1, 0, or 1
+    as the first value is less than, equal to, or greater than the second value.
+    If the comparator function returns other values (including ``NULL``), the query will fail and raise an error ::
+
+        SELECT map_top_n_values(map(ARRAY['a', 'b', 'c'], ARRAY[1, 2, 3]), 2, (x, y) -> IF(x < y, -1, IF(x = y, 0, 1))) --- [3, 2]
+
 .. function:: map_zip_with(map(K,V1), map(K,V2), function(K,V1,V2,V3)) -> map(K,V3)
 
     Merges the two given maps into a single map by applying ``function`` to the pair of values with the same key.

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

@@ -45,4 +45,26 @@ public static String mapTopNKeysComparator()
     {
         return "RETURN IF(n < 0, fail('n must be greater than or equal to 0'), slice(reverse(array_sort(map_keys(input), f)), 1, n))";
     }
+
+    @SqlInvokedScalarFunction(value = "map_top_n_values", deterministic = true, calledOnNullInput = false)
+    @Description("Returns the top N values of the given map in descending order according to the natural ordering of its values.")
+    @TypeParameter("K")
+    @TypeParameter("V")
+    @SqlParameters({@SqlParameter(name = "input", type = "map(K, V)"), @SqlParameter(name = "n", type = "bigint")})
+    @SqlType("array<V>")
+    public static String mapTopNValues()
+    {
+        return "RETURN IF(n < 0, fail('n must be greater than or equal to 0'), slice(array_sort_desc(map_values(input)), 1, n))";
+    }
+
+    @SqlInvokedScalarFunction(value = "map_top_n_values", deterministic = true, calledOnNullInput = true)
+    @Description("Returns the top N values of the given map sorted using the provided lambda comparator.")
+    @TypeParameter("K")
+    @TypeParameter("V")
+    @SqlParameters({@SqlParameter(name = "input", type = "map(K, V)"), @SqlParameter(name = "n", type = "bigint"), @SqlParameter(name = "f", type = "function(V, V, int)")})
+    @SqlType("array<V>")
+    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))";
+    }
 }

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

@@ -0,0 +1,106 @@
+/*
+ * 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.common.type.RowType;
+import com.facebook.presto.operator.scalar.AbstractTestFunctions;
+import com.facebook.presto.spi.StandardErrorCode;
+import com.facebook.presto.sql.analyzer.SemanticErrorCode;
+import com.google.common.collect.ImmutableList;
+import org.testng.annotations.Test;
+
+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;
+
+public class TestMapTopNValuesComparatorFunction
+        extends AbstractTestFunctions
+{
+    @Test
+    public void testBasic()
+    {
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 2, (x, y) -> IF(x < y, 1, IF(x = y, 0, -1)))", new ArrayType(INTEGER), ImmutableList.of(1, 2));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 2, (x, y) -> IF(x > y, 1, IF(x = y, 0, -1)))", new ArrayType(INTEGER), ImmutableList.of(3, 2));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY['x', 'y', 'z'], ARRAY['a', 'b', 'c']), 3, (x, y) -> IF(x > y, 1, IF(x = y, 0, -1)))", new ArrayType(createVarcharType(1)), ImmutableList.of("c", "b", "a"));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY['x', 'y', 'z'], ARRAY['a1', 'b2', 'c3']), 1, (x, y) -> IF(x > y, 1, IF(x = y, 0, -1)))", new ArrayType(createVarcharType(2)), ImmutableList.of("c3"));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY['a', 'b', 'c', 'd'], ARRAY['xyz', 'xy', 'yz', 'z']), 4, (x, y) -> CASE " +
+                        "WHEN LENGTH(x) > LENGTH(y) THEN 1 " +
+                        "WHEN LENGTH(x) < LENGTH(y) THEN -1 " +
+                        "WHEN x > y THEN 1 " +
+                        "WHEN x < y THEN -1 " +
+                        "ELSE -1 END)",
+                new ArrayType(createVarcharType(3)), ImmutableList.of("xyz", "yz", "xy", "z"));
+    }
+
+    @Test
+    public void testNLargerThanMapSize()
+    {
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 8, (x, y) -> IF(x < y, 1, IF(x = y, 0, -1)))", new ArrayType(INTEGER), ImmutableList.of(1, 2, 3));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 9, (x, y) -> IF(x > y, 1, IF(x = y, 0, -1)))", new ArrayType(INTEGER), ImmutableList.of(3, 2, 1));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY['x', 'y', 'z'], ARRAY['abc', 'bcd', 'cde']), 10, (x, y) -> IF(x > y, 1, IF(x = y, 0, -1)))", new ArrayType(createVarcharType(3)), ImmutableList.of("cde", "bcd", "abc"));
+    }
+
+    @Test
+    public void testNegativeN()
+    {
+        assertInvalidFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), -1, (x, y) -> IF(x < y, 1, IF(x = y, 0, -1)))", StandardErrorCode.GENERIC_USER_ERROR, "n must be greater than or equal to 0");
+        assertInvalidFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1.99, -2.12, 3.01]), -2, (x, y) -> IF(x > y, 1, IF(x = y, 0, -1)))", StandardErrorCode.GENERIC_USER_ERROR, "n must be greater than or equal to 0");
+        assertInvalidFunction("MAP_TOP_N_VALUES(MAP(ARRAY[1, 2, 3], ARRAY['x', 'y', 'z']), -3, (x, y) -> IF(x > y, 1, IF(x = y, 0, -1)))", StandardErrorCode.GENERIC_USER_ERROR, "n must be greater than or equal to 0");
+        assertInvalidFunction("MAP_TOP_N_VALUES(MAP(ARRAY['a', 'b', 'c', 'd'], ARRAY['xyz', 'xy', 'yz', 'z']), -2, (x, y) -> CASE " +
+                        "WHEN LENGTH(x) > LENGTH(y) THEN 1 " +
+                        "WHEN LENGTH(x) < LENGTH(y) THEN -1 " +
+                        "WHEN x > y THEN 1 " +
+                        "WHEN x < y THEN -1 " +
+                        "ELSE -1 END)",
+                StandardErrorCode.GENERIC_USER_ERROR, "n must be greater than or equal to 0");
+    }
+
+    @Test
+    public void testZeroN()
+    {
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 0, (x, y) -> IF(x < y, 1, IF(x = y, 0, -1)))", new ArrayType(INTEGER), ImmutableList.of());
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 0, (x, y) -> IF(x > y, 1, IF(x = y, 0, -1)))", new ArrayType(INTEGER), ImmutableList.of());
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[1, 2, 3], ARRAY['x', 'y', 'z']), 0, (x, y) -> IF(x > y, 1, IF(x = y, 0, -1)))", new ArrayType(createVarcharType(1)), ImmutableList.of());
+    }
+
+    @Test
+    public void testEmpty()
+    {
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[], ARRAY[]), 1, (x, y) -> IF(x < y, 1, IF(x = y, 0, -1)))", new ArrayType(UNKNOWN), ImmutableList.of());
+    }
+
+    @Test
+    public void testNull()
+    {
+        assertFunction("MAP_TOP_N_VALUES(NULL, 1, (x, y) -> IF(x < y, 1, IF(x = y, 0, -1)))", new ArrayType(UNKNOWN), null);
+    }
+
+    @Test
+    public void testComplexValues()
+    {
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY['a', 'b', 'c'], ARRAY[ROW('x', 1), ROW('y', 2), ROW('z', 3)]), 3," +
+                        "(x, y) -> IF(x[1] < y[1], 1, IF(x[1] = y[1], 0, -1)))",
+                new ArrayType(RowType.from(ImmutableList.of(RowType.field(createVarcharType(1)), RowType.field(INTEGER)))),
+                ImmutableList.of(ImmutableList.of("x", 1), ImmutableList.of("y", 2), ImmutableList.of("z", 3)));
+    }
+
+    @Test
+    public void testBadLambda()
+    {
+        assertInvalidFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 1, (x, y) -> 10)", StandardErrorCode.INVALID_FUNCTION_ARGUMENT, "Lambda comparator must return either -1, 0, or 1");
+        assertInvalidFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 2, null)", SemanticErrorCode.FUNCTION_NOT_FOUND);
+        assertInvalidFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 3, (x, y) -> IF(x = 'test', 1, -1))", SemanticErrorCode.TYPE_MISMATCH);
+    }
+}

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

@@ -0,0 +1,82 @@
+/*
+ * 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.common.type.RowType;
+import com.facebook.presto.operator.scalar.AbstractTestFunctions;
+import com.facebook.presto.spi.StandardErrorCode;
+import com.google.common.collect.ImmutableList;
+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 java.util.Arrays.asList;
+
+public class TestMapTopNValuesFunction
+        extends AbstractTestFunctions
+{
+    @Test
+    public void testBasic()
+    {
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 2)", new ArrayType(INTEGER), ImmutableList.of(3, 2));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[-1, -2, -3]), 2)", new ArrayType(INTEGER), ImmutableList.of(-1, -2));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY['x', 'y', 'z'], ARRAY['ab', 'bc', 'cd']), 1)", new ArrayType(createVarcharType(2)), ImmutableList.of("cd"));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY['x', 'y', 'z'], ARRAY[123.0, 99.5, 1000.99]), 3)", new ArrayType(createDecimalType(6, 2)), ImmutableList.of(decimal("1000.99"), decimal("123.00"), decimal("99.50")));
+    }
+
+    @Test
+    public void tesMayHaveNull()
+    {
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, null, 3]), 3)", new ArrayType(INTEGER), asList(3, 1, null));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[-1, -2, null]), 2)", new ArrayType(INTEGER), asList(-1, -2));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY['x', 'y', 'z'], ARRAY[null, 'bc', 'cd']), 3)", new ArrayType(createVarcharType(2)), asList("cd", "bc", null));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY['x', 'y', 'z'], ARRAY[123.0, 99.5, null]), 3)", new ArrayType(createDecimalType(4, 1)), asList(decimal("123.0"), decimal("99.5"), null));
+    }
+
+    @Test
+    public void testNegativeN()
+    {
+        assertInvalidFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, null, 3]), -1)", StandardErrorCode.GENERIC_USER_ERROR, "n must be greater than or equal to 0");
+        assertInvalidFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY['a', 'b', 'c']), -2)", StandardErrorCode.GENERIC_USER_ERROR, "n must be greater than or equal to 0");
+    }
+
+    @Test
+    public void testZeroN()
+    {
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY[1, null, 3]), 0)", new ArrayType(INTEGER), ImmutableList.of());
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[4, 5, 6], ARRAY['a', 'b', 'c']), 0)", new ArrayType(createVarcharType(1)), ImmutableList.of());
+    }
+
+    @Test
+    public void testEmpty()
+    {
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[], ARRAY[]), 5)", new ArrayType(UNKNOWN), ImmutableList.of());
+    }
+
+    @Test
+    public void testNull()
+    {
+        assertFunction("MAP_TOP_N_VALUES(NULL, 1)", new ArrayType(UNKNOWN), null);
+    }
+
+    @Test
+    public void testComplexValues()
+    {
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[1, 2], ARRAY[ROW('x', 1), ROW('y', 2)]), 1)", new ArrayType(RowType.from(ImmutableList.of(RowType.field(createVarcharType(1)), RowType.field(INTEGER)))), ImmutableList.of(ImmutableList.of("y", 2)));
+        assertFunction("MAP_TOP_N_VALUES(MAP(ARRAY[1, 2], ARRAY[ROW('x', 1), ROW('x', -2)]), 1)", new ArrayType(RowType.from(ImmutableList.of(RowType.field(createVarcharType(1)), RowType.field(INTEGER)))), ImmutableList.of(ImmutableList.of("x", 1)));
+    }
+}