/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Sep 10, 2011
*/
package com.bigdata.rdf.sparql.ast.optimizers;
import java.util.Iterator;
import com.bigdata.bop.BOp;
import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.bindingSet.ListBindingSet;
import com.bigdata.rdf.sparql.ast.ArbitraryLengthPathNode;
import com.bigdata.rdf.sparql.ast.ConstantNode;
import com.bigdata.rdf.sparql.ast.FilterNode;
import com.bigdata.rdf.sparql.ast.GraphPatternGroup;
import com.bigdata.rdf.sparql.ast.IGroupMemberNode;
import com.bigdata.rdf.sparql.ast.IQueryNode;
import com.bigdata.rdf.sparql.ast.IValueExpressionNode;
import com.bigdata.rdf.sparql.ast.JoinGroupNode;
import com.bigdata.rdf.sparql.ast.NamedSubqueriesNode;
import com.bigdata.rdf.sparql.ast.NamedSubqueryRoot;
import com.bigdata.rdf.sparql.ast.QueryBase;
import com.bigdata.rdf.sparql.ast.QueryNodeWithBindingSet;
import com.bigdata.rdf.sparql.ast.QueryRoot;
import com.bigdata.rdf.sparql.ast.StaticAnalysis;
import com.bigdata.rdf.sparql.ast.SubqueryFunctionNodeBase;
import com.bigdata.rdf.sparql.ast.eval.AST2BOpContext;
import com.bigdata.rdf.sparql.ast.service.ServiceNode;
/**
* This makes it easier to sit down and write an optimizer that operates on
* a group.
*/
public abstract class AbstractJoinGroupOptimizer implements IASTOptimizer {
private final boolean childFirst;
private final boolean optimizeServiceNodes;
public AbstractJoinGroupOptimizer() {
this(false, false);
}
protected AbstractJoinGroupOptimizer(final boolean childFirst, final boolean optimizeServiceNodes) {
this.childFirst = childFirst;
this.optimizeServiceNodes = optimizeServiceNodes;
}
/**
* Top-level optimize method. Will locate the relevant top-level
* {@link GraphPatternGroup} nodes (where clause, named subqueries) and
* delegate to the
* {@link #optimize(AST2BOpContext, StaticAnalysis, GraphPatternGroup)} method.
*/
@Override
public QueryNodeWithBindingSet optimize(
final AST2BOpContext context, final QueryNodeWithBindingSet input) {
final IQueryNode queryNode = input.getQueryNode();
final IBindingSet[] bindingSets = input.getBindingSets();
if (!(queryNode instanceof QueryRoot))
return new QueryNodeWithBindingSet(queryNode, bindingSets);
final QueryRoot queryRoot = (QueryRoot) queryNode;
final StaticAnalysis sa = new StaticAnalysis(queryRoot, context);
// Main WHERE clause
{
@SuppressWarnings("unchecked")
final GraphPatternGroup<IGroupMemberNode> whereClause =
(GraphPatternGroup<IGroupMemberNode>) queryRoot.getWhereClause();
if (whereClause != null) {
optimize(context, sa, bindingSets, whereClause);
}
}
// Named subqueries
if (queryRoot.getNamedSubqueries() != null) {
final NamedSubqueriesNode namedSubqueries = queryRoot
.getNamedSubqueries();
/*
* Note: This loop uses the current size() and get(i) to avoid
* problems with concurrent modification during visitation.
*/
for (NamedSubqueryRoot namedSubquery : namedSubqueries) {
@SuppressWarnings("unchecked")
final GraphPatternGroup<IGroupMemberNode> whereClause =
(GraphPatternGroup<IGroupMemberNode>) namedSubquery.getWhereClause();
if (whereClause != null) {
optimize(context, sa, bindingSets, whereClause);
}
}
}
// log.error("\nafter rewrite:\n" + queryNode);
return new QueryNodeWithBindingSet(queryNode, bindingSets);
}
/**
* Optimize a particular {@link GraphPatternGroup}. If the group happens
* to be a {@link JoinGroupNode}, this method will delegate to the
* {@link #optimize(AST2BOpContext, StaticAnalysis, JoinGroupNode)}
* method, which is the method that subclasses should override to do the
* work of actually optimizing a particular join group. After optimizing
* the group, this method will descend into the children and recursively
* optimize any child groups as well.
* <p>
* I've made this method final, but I could perhaps see cases where
* subclasses might want to override. Maybe revisit. -mp
*/
private void optimize(final AST2BOpContext ctx,
final StaticAnalysis sa, final IBindingSet[] bSets,
final GraphPatternGroup<?> op) {
if (!childFirst) {
if (op instanceof JoinGroupNode) {
final JoinGroupNode joinGroup = (JoinGroupNode) op;
optimizeJoinGroup(ctx, sa, bSets, joinGroup);
}
}
/*
* Recursion, but only into group nodes (including within subqueries).
*/
for (int i = 0; i < op.arity(); i++) {
final BOp child = op.get(i);
if (child instanceof GraphPatternGroup<?>) {
@SuppressWarnings("unchecked")
final GraphPatternGroup<IGroupMemberNode> childGroup = (GraphPatternGroup<IGroupMemberNode>) child;
optimize(ctx, sa, bSets, childGroup);
} else if (child instanceof QueryBase) {
final QueryBase subquery = (QueryBase) child;
@SuppressWarnings("unchecked")
final GraphPatternGroup<IGroupMemberNode> childGroup = (GraphPatternGroup<IGroupMemberNode>) subquery
.getWhereClause();
optimize(ctx, sa, bSets, childGroup);
} else if (child instanceof FilterNode) {
final FilterNode filter = (FilterNode) child;
final IValueExpressionNode ve = filter.getValueExpressionNode();
optimize(ctx, sa, bSets, ve);
} else if (child instanceof ArbitraryLengthPathNode) {
final ArbitraryLengthPathNode alpNode = (ArbitraryLengthPathNode) child;
final IBindingSet bs = new ListBindingSet();
if (alpNode.left().isConstant()) {
bs.set(alpNode.tVarLeft().getValueExpression(),
((ConstantNode) alpNode.left()).getValueExpression());
}
if (alpNode.right().isConstant()) {
bs.set(alpNode.tVarRight().getValueExpression(),
((ConstantNode) alpNode.right()).getValueExpression());
}
/*
* The transitivity vars are unique to the alpNode, so we don't
* need to merge, simple addition will do fine.
*/
final IBindingSet[] bSets2;
if (bSets == null || bSets.length == 0 ||
(bSets.length == 1 && bSets[0].isEmpty())) {
bSets2 = new IBindingSet[] { bs };
} else {
bSets2 = new IBindingSet[bSets.length+1];
bSets2[0] = bs;
System.arraycopy(bSets, 0, bSets2, 1, bSets.length);
}
optimize(ctx, sa, bSets2, alpNode.subgroup());
} else if (child instanceof ServiceNode && optimizeServiceNodes) {
final ServiceNode serviceNode = (ServiceNode) child;
@SuppressWarnings("unchecked")
final GraphPatternGroup<IGroupMemberNode> childGroup = (GraphPatternGroup<IGroupMemberNode>) serviceNode
.getGraphPattern();
optimize(ctx, sa, bSets, childGroup);
}
}
if (childFirst) {
if (op instanceof JoinGroupNode) {
final JoinGroupNode joinGroup = (JoinGroupNode) op;
optimizeJoinGroup(ctx, sa, bSets, joinGroup);
}
}
}
private void optimize(final AST2BOpContext ctx, final StaticAnalysis sa,
final IBindingSet[] bSets, final IValueExpressionNode ve) {
if (ve instanceof SubqueryFunctionNodeBase) {
final SubqueryFunctionNodeBase subqueryFunction = (SubqueryFunctionNodeBase) ve;
final GraphPatternGroup<IGroupMemberNode> graphPattern = subqueryFunction
.getGraphPattern();
if (graphPattern != null) {
optimize(ctx, sa, bSets, graphPattern);
}
} else {
Iterator<BOp> it = ((BOp)ve).argIterator();
while (it.hasNext()) {
BOp b = it.next();
if (b instanceof IValueExpressionNode) {
optimize(ctx, sa, bSets, (IValueExpressionNode)b);
}
}
}
}
/**
* Subclasses can do the work of optimizing a join group here.
*/
protected abstract void optimizeJoinGroup(
final AST2BOpContext ctx, final StaticAnalysis sa,
final IBindingSet[] bSets, final JoinGroupNode op);
}