A simple sql to sql rewrite for cardinality()

presto-main/src/main/java/com/facebook/presto/sql/planner/PlanOptimizers.java

@@ -101,6 +101,7 @@
 import com.facebook.presto.sql.planner.iterative.rule.RewriteFilterWithExternalFunctionToProject;
 import com.facebook.presto.sql.planner.iterative.rule.RewriteSpatialPartitioningAggregation;
 import com.facebook.presto.sql.planner.iterative.rule.RuntimeReorderJoinSides;
+import com.facebook.presto.sql.planner.iterative.rule.SimplifyCardinalityMap;
 import com.facebook.presto.sql.planner.iterative.rule.SimplifyCountOverConstant;
 import com.facebook.presto.sql.planner.iterative.rule.SimplifyExpressions;
 import com.facebook.presto.sql.planner.iterative.rule.SimplifyRowExpressions;
@@ -288,6 +289,7 @@ public PlanOptimizers(
                                 .addAll(new DesugarAtTimeZone(metadata, sqlParser).rules())
                                 .addAll(new DesugarCurrentUser().rules())
                                 .addAll(new DesugarTryExpression().rules())
+                                .addAll(new SimplifyCardinalityMap().rules())
                                 .addAll(new DesugarRowSubscript(metadata, sqlParser).rules())
                                 .build()),
                 new IterativeOptimizer(

presto-main/src/main/java/com/facebook/presto/sql/planner/iterative/rule/SimplifyCardinalityMap.java

@@ -0,0 +1,25 @@
+/*
+ * 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.sql.planner.iterative.rule;
+
+import static com.facebook.presto.sql.planner.iterative.rule.SimplifyCardinalityMapRewriter.rewrite;
+
+public class SimplifyCardinalityMap
+        extends ExpressionRewriteRuleSet
+{
+    public SimplifyCardinalityMap()
+    {
+        super((expression, context) -> rewrite(expression));
+    }
+}

presto-main/src/main/java/com/facebook/presto/sql/planner/iterative/rule/SimplifyCardinalityMapRewriter.java

@@ -0,0 +1,84 @@
+/*
+ * 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.sql.planner.iterative.rule;
+import com.facebook.presto.sql.tree.Expression;
+import com.facebook.presto.sql.tree.ExpressionRewriter;
+import com.facebook.presto.sql.tree.ExpressionTreeRewriter;
+import com.facebook.presto.sql.tree.FunctionCall;
+import com.facebook.presto.sql.tree.QualifiedName;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+
+import java.util.Set;
+
+/**
+ * Transforms:
+ * <pre>
+ * - Cardinality(Map_Values(map))
+ *     - X
+ * </pre>
+ * Into:
+ * <pre>
+ * - Cardinality(map)
+ *     - X
+ * </pre>
+ */
+public class SimplifyCardinalityMapRewriter
+{
+    private static final Set<QualifiedName> MAP_FUNCTIONS = ImmutableSet.of(QualifiedName.of("map_values"), QualifiedName.of("map_keys"));
+
+    private SimplifyCardinalityMapRewriter() {}
+
+    public static Expression rewrite(Expression expression)
+    {
+        return ExpressionTreeRewriter.rewriteWith(new Visitor(), expression);
+    }
+
+    private static class Visitor
+            extends ExpressionRewriter<Void>
+    {
+        @Override
+        public Expression rewriteFunctionCall(FunctionCall node, Void context, ExpressionTreeRewriter<Void> treeRewriter)
+        {
+            ImmutableList.Builder<Expression> rewrittenArguments = ImmutableList.builder();
+
+            if (node.getName().equals(QualifiedName.of("cardinality"))) {
+                for (Expression argument : node.getArguments()) {
+                    if (argument instanceof FunctionCall) {
+                        FunctionCall functionCall = (FunctionCall) argument;
+                        if (MAP_FUNCTIONS.contains(functionCall.getName()) && functionCall.getArguments().size() == 1) {
+                            rewrittenArguments.add(treeRewriter.rewrite(functionCall.getArguments().get(0), context));
+                            continue;
+                        }
+                    }
+                    rewrittenArguments.add(treeRewriter.rewrite(argument, context));
+                }
+                return newFunctionIfRewritten(node, rewrittenArguments);
+            }
+            for (Expression argument : node.getArguments()) {
+                rewrittenArguments.add(treeRewriter.rewrite(argument, context));
+            }
+            return newFunctionIfRewritten(node, rewrittenArguments);
+        }
+
+        private Expression newFunctionIfRewritten(FunctionCall node, ImmutableList.Builder<Expression> rewrittenArguments)
+        {
+            if (!node.getArguments().equals(rewrittenArguments.build())) {
+                return new FunctionCall(node.getName(), rewrittenArguments.build());
+            }
+            return node;
+        }
+    }
+}

presto-main/src/test/java/com/facebook/presto/sql/planner/iterative/rule/TestSimplifyCardinalityMap.java

@@ -0,0 +1,72 @@
+/*
+ * 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.sql.planner.iterative.rule;
+
+import com.facebook.presto.sql.planner.iterative.rule.test.BaseRuleTest;
+import com.facebook.presto.sql.planner.iterative.rule.test.PlanBuilder;
+import org.testng.annotations.Test;
+
+import static com.facebook.presto.sql.planner.iterative.rule.SimplifyCardinalityMapRewriter.rewrite;
+import static org.testng.Assert.assertEquals;
+
+public class TestSimplifyCardinalityMap
+        extends BaseRuleTest
+{
+    @Test
+    public void testRewriteMapValuesCardinality()
+    {
+        assertRewritten("cardinality(map_values(m))", "cardinality(m)");
+    }
+
+    @Test
+    public void testRewriteMapValuesMixedCasesCardinality()
+    {
+        assertRewritten("CaRDinality(map_values(m))", "cardinaLITY(m)");
+    }
+
+    @Test
+    public void testNoRewriteMapValuesCardinality()
+    {
+        assertRewritten("cardinality(map(ARRAY[1,3], ARRAY[2,4]))", "cardinality(map(ARRAY[1,3], ARRAY[2,4]))");
+    }
+
+    @Test
+    public void testNestedRewriteMapValuesCardinality()
+    {
+        assertRewritten(
+                "cardinality(map(ARRAY[cardinality(map_values(m_1)),3], ARRAY[2,cardinality(map_values(m_2))]))",
+                "cardinality(map(ARRAY[cardinality(m_1),3], ARRAY[2,cardinality(m_2)]))");
+    }
+
+    @Test
+    public void testNestedRewriteMapKeysCardinality()
+    {
+        assertRewritten(
+                "cardinality(map(ARRAY[cardinality(map_keys(m_1)),3], ARRAY[2,cardinality(map_keys(m_2))]))",
+                "cardinality(map(ARRAY[cardinality(m_1),3], ARRAY[2,cardinality(m_2)]))");
+    }
+
+    @Test
+    public void testAnotherNestedRewriteMapValuesCardinality()
+    {
+        assertRewritten(
+                "cardinality(map(ARRAY[cardinality(map_values(map(ARRAY[1,3], ARRAY[2,4]))),3], ARRAY[2,cardinality(map_values(m_2))]))",
+                "cardinality(map(ARRAY[cardinality(map(ARRAY[1,3], ARRAY[2,4])),3], ARRAY[2,cardinality(m_2)]))");
+    }
+
+    private static void assertRewritten(String from, String to)
+    {
+        assertEquals(rewrite(PlanBuilder.expression(from)), PlanBuilder.expression(to));
+    }
+}