/**
* Licensed to Odiago, Inc. under one or more contributor license
* agreements. See the NOTICE.txt file distributed with this work for
* additional information regarding copyright ownership. Odiago, Inc.
* 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.odiago.flumebase.lang;
import java.util.Collections;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.odiago.flumebase.parser.AllFieldsExpr;
import com.odiago.flumebase.parser.ConstExpr;
import com.odiago.flumebase.parser.Expr;
import com.odiago.flumebase.parser.FnCallExpr;
/**
* Syntactically replace COUNT(*) with COUNT(1) in the SELECT expressions;
* we can't typecheck a '*' inside an expression, but an arbitrary constant
* expression will suffice as an argument here.
*/
public class CountStarVisitor extends TreeWalkVisitor {
private static final Logger LOG = LoggerFactory.getLogger(
CountStarVisitor.class.getName());
@Override
protected void visit(FnCallExpr e) throws VisitException {
if (e.getFunctionName().equals("count")) {
// Yep, it's a COUNT() function. Check if its argument is a '*'.
List<Expr> fnArgs = e.getArgExpressions();
if (fnArgs.size() == 1 && fnArgs.get(0) instanceof AllFieldsExpr) {
// This matches COUNT(*).
LOG.debug("Replaced count(*) in SELECT statement.");
e.setArgExpressions(Collections.singletonList((Expr)
new ConstExpr(Type.getPrimitive(Type.TypeName.INT), Integer.valueOf(1))));
}
}
}
}