studio.raptor.sqlparser.visitor.functions.Greatest Maven / Gradle / Ivy

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/*
 * Copyright 1999-2017 Alibaba Group Holding Ltd.
 *
 * 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 studio.raptor.sqlparser.visitor.functions;

import static studio.raptor.sqlparser.visitor.SQLEvalVisitor.EVAL_VALUE;

import studio.raptor.sqlparser.ast.SQLExpr;
import studio.raptor.sqlparser.ast.expr.SQLMethodInvokeExpr;
import studio.raptor.sqlparser.visitor.SQLEvalVisitor;
import studio.raptor.sqlparser.visitor.SQLEvalVisitorUtils;

public class Greatest implements Function {

  public final static Greatest instance = new Greatest();

  public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
    Object result = null;
    for (SQLExpr item : x.getParameters()) {
      item.accept(visitor);

      Object itemValue = item.getAttributes().get(EVAL_VALUE);
      if (result == null) {
        result = itemValue;
      } else {
        if (SQLEvalVisitorUtils.gt(itemValue, result)) {
          result = itemValue;
        }
      }
    }

    return result;
  }
}