com.hazelcast.org.apache.calcite.sql.util.SqlBasicVisitor Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you 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.hazelcast.org.apache.calcite.sql.util;
import com.hazelcast.org.apache.calcite.sql.SqlCall;
import com.hazelcast.org.apache.calcite.sql.SqlDataTypeSpec;
import com.hazelcast.org.apache.calcite.sql.SqlDynamicParam;
import com.hazelcast.org.apache.calcite.sql.SqlIdentifier;
import com.hazelcast.org.apache.calcite.sql.SqlIntervalQualifier;
import com.hazelcast.org.apache.calcite.sql.SqlLiteral;
import com.hazelcast.org.apache.calcite.sql.SqlNode;
import com.hazelcast.org.apache.calcite.sql.SqlNodeList;
/**
* Basic implementation of {@link SqlVisitor} which does nothing at each node.
*
* This class is useful as a base class for classes which implement the
* {@link SqlVisitor} interface. The derived class can override whichever
* methods it chooses.
*
* @param Return type
*/
public class SqlBasicVisitor implements SqlVisitor {
//~ Methods ----------------------------------------------------------------
public R visit(SqlLiteral literal) {
return null;
}
public R visit(SqlCall call) {
return call.getOperator().acceptCall(this, call);
}
public R visit(SqlNodeList nodeList) {
R result = null;
for (int i = 0; i < nodeList.size(); i++) {
SqlNode node = nodeList.get(i);
result = node.accept(this);
}
return result;
}
public R visit(SqlIdentifier id) {
return null;
}
public R visit(SqlDataTypeSpec type) {
return null;
}
public R visit(SqlDynamicParam param) {
return null;
}
public R visit(SqlIntervalQualifier intervalQualifier) {
return null;
}
//~ Inner Interfaces -------------------------------------------------------
/** Argument handler.
*
* @param result type */
public interface ArgHandler {
/** Returns the result of visiting all children of a call to an operator,
* then the call itself.
*
* Typically the result will be the result of the last child visited, or
* (if R is {@link Boolean}) whether all children were visited
* successfully. */
R result();
/** Visits a particular operand of a call, using a given visitor. */
R visitChild(
SqlVisitor visitor,
SqlNode expr,
int i,
SqlNode operand);
}
//~ Inner Classes ----------------------------------------------------------
/**
* Default implementation of {@link ArgHandler} which merely calls
* {@link SqlNode#accept} on each operand.
*
* @param result type
*/
public static class ArgHandlerImpl implements ArgHandler {
private static final ArgHandler INSTANCE = new ArgHandlerImpl();
@SuppressWarnings("unchecked")
public static ArgHandler instance() {
return INSTANCE;
}
public R result() {
return null;
}
public R visitChild(
SqlVisitor visitor,
SqlNode expr,
int i,
SqlNode operand) {
if (operand == null) {
return null;
}
return operand.accept(visitor);
}
}
}