/**
* Copyright (C) 2009-2013 FoundationDB, LLC
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package com.foundationdb.sql.optimizer.rule;
import com.foundationdb.sql.optimizer.plan.BaseQuery;
import com.foundationdb.sql.optimizer.plan.ColumnExpression;
import com.foundationdb.sql.optimizer.plan.PlanNode;
import java.util.ArrayDeque;
import java.util.Deque;
public final class ColumnEquivalenceStack {
private static final int EQUIVS_DEQUE_SIZE = 3;
private Deque<EquivalenceFinder<ColumnExpression>> stack
= new ArrayDeque<>(EQUIVS_DEQUE_SIZE);
private Deque<EquivalenceFinder<ColumnExpression>> fkStack =
new ArrayDeque<>(EQUIVS_DEQUE_SIZE);
public boolean enterNode(PlanNode n) {
if (n instanceof BaseQuery) {
BaseQuery bq = (BaseQuery) n;
stack.push(bq.getColumnEquivalencies());
fkStack.push(bq.getFKEquivalencies());
return true;
}
return false;
}
public EquivalenceFinder<ColumnExpression> leaveNode(PlanNode n) {
if (n instanceof BaseQuery) {
fkStack.removeFirst();
return stack.pop();
}
return null;
}
public EquivalenceFinder<ColumnExpression> get() {
return stack.element();
}
public EquivalenceFinder<ColumnExpression> getFks() {
return fkStack.element();
}
public boolean isEmpty() {
return stack.isEmpty();
}
}