Eliminate redundant parameter extraction

ParameterExtractor has similar implementations for getParameterCount and
getParameters. The former method can make use of the getParameters to
get the size of parameters.

presto-main/src/main/java/io/prestosql/execution/ParameterExtractor.java

@@ -26,9 +26,7 @@ private ParameterExtractor() {}
 
     public static int getParameterCount(Statement statement)
     {
-        ParameterExtractingVisitor parameterExtractingVisitor = new ParameterExtractingVisitor();
-        parameterExtractingVisitor.process(statement, null);
-        return parameterExtractingVisitor.getParameters().size();
+        return getParameters(statement).size();
     }
 
     public static List<Parameter> getParameters(Statement statement)

presto-main/src/test/java/io/prestosql/execution/TestParameterExtractor.java

@@ -0,0 +1,47 @@
+/*
+ * 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 io.prestosql.execution;
+
+import io.prestosql.sql.parser.ParsingOptions;
+import io.prestosql.sql.parser.SqlParser;
+import io.prestosql.sql.tree.NodeLocation;
+import io.prestosql.sql.tree.Parameter;
+import io.prestosql.sql.tree.Statement;
+import org.testng.annotations.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class TestParameterExtractor
+{
+    private final SqlParser sqlParser = new SqlParser();
+
+    @Test
+    public void testNoParameter()
+    {
+        Statement statement = sqlParser.createStatement("SELECT c1, c2 FROM test_table WHERE c1 = 1 AND c2 > 2", new ParsingOptions());
+        assertThat(ParameterExtractor.getParameters(statement)).isEmpty();
+        assertThat(ParameterExtractor.getParameterCount(statement)).isEqualTo(0);
+    }
+
+    @Test
+    public void testParameterCount()
+    {
+        Statement statement = sqlParser.createStatement("SELECT c1, c2 FROM test_table WHERE c1 = ? AND c2 > ?", new ParsingOptions());
+        assertThat(ParameterExtractor.getParameters(statement))
+                .containsExactly(
+                        new Parameter(new NodeLocation(1, 41), 0),
+                        new Parameter(new NodeLocation(1, 52), 1));
+        assertThat(ParameterExtractor.getParameterCount(statement)).isEqualTo(2);
+    }
+}