/* This file is part of VoltDB.
* Copyright (C) 2008-2017 VoltDB Inc.
*
* 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 VoltDB. If not, see <http://www.gnu.org/licenses/>.
*/
package org.voltdb.planner.microoptimizations;
import org.voltdb.planner.AbstractParsedStmt;
import org.voltdb.planner.CompiledPlan;
import org.voltdb.plannodes.AbstractPlanNode;
public abstract class MicroOptimization {
protected AbstractParsedStmt m_parsedStmt;
/// Provide a commonly used approach to optimization via a potentially
/// recursive call to recursivelyApply that is expected to edit or replace
/// the plan graph.
/// The parsed statement is also available as a data member to provide context.
/// Derived classes must implement recursiveApply, but that implementation
/// could just "assert(false)" IF the class also completely re-implemented
/// "apply". Implementing recursivelyApply to do real work on the plan
/// graph is the more common way to specialize this class.
protected void apply(CompiledPlan plan, AbstractParsedStmt parsedStmt)
{
try {
m_parsedStmt = parsedStmt;
AbstractPlanNode planGraph = plan.rootPlanGraph;
planGraph = recursivelyApply(planGraph);
plan.rootPlanGraph = planGraph;
}
finally {
// Avoid leaking a long-term reference from static optimizations
// to a large parsed statement structure.
m_parsedStmt = null;
}
}
protected abstract AbstractPlanNode recursivelyApply(AbstractPlanNode plan);
}