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Posted to commits@jena.apache.org by rv...@apache.org on 2015/07/07 11:24:10 UTC
[05/26] jena git commit: Eliminate single use assignments referenced
in ORDER BY (JENA-780)
Eliminate single use assignments referenced in ORDER BY (JENA-780)
This commit improves TransformEliminateAssignments to be able to
eliminate single use assignments that are used only in ORDER BY sort
conditions
Project: http://git-wip-us.apache.org/repos/asf/jena/repo
Commit: http://git-wip-us.apache.org/repos/asf/jena/commit/62dfb5aa
Tree: http://git-wip-us.apache.org/repos/asf/jena/tree/62dfb5aa
Diff: http://git-wip-us.apache.org/repos/asf/jena/diff/62dfb5aa
Branch: refs/heads/jena2
Commit: 62dfb5aa099ccd121a6c798a0e12b63d179c6dab
Parents: 79f8765
Author: Rob Vesse <rv...@apache.org>
Authored: Tue Sep 30 10:34:53 2014 +0100
Committer: Rob Vesse <rv...@apache.org>
Committed: Tue Sep 30 10:34:53 2014 +0100
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.../optimize/TransformEliminateAssignments.java | 57 +++++++++++++++++++-
.../TestTransformEliminateAssignments.java | 17 ++++++
2 files changed, 73 insertions(+), 1 deletion(-)
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http://git-wip-us.apache.org/repos/asf/jena/blob/62dfb5aa/jena-arq/src/main/java/com/hp/hpl/jena/sparql/algebra/optimize/TransformEliminateAssignments.java
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diff --git a/jena-arq/src/main/java/com/hp/hpl/jena/sparql/algebra/optimize/TransformEliminateAssignments.java b/jena-arq/src/main/java/com/hp/hpl/jena/sparql/algebra/optimize/TransformEliminateAssignments.java
index d24c500..c9bdb7c 100644
--- a/jena-arq/src/main/java/com/hp/hpl/jena/sparql/algebra/optimize/TransformEliminateAssignments.java
+++ b/jena-arq/src/main/java/com/hp/hpl/jena/sparql/algebra/optimize/TransformEliminateAssignments.java
@@ -22,9 +22,12 @@ import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
+import java.util.List;
import java.util.Map;
import org.apache.jena.atlas.lib.CollectionUtils;
+
+import com.hp.hpl.jena.query.SortCondition;
import com.hp.hpl.jena.sparql.algebra.Op;
import com.hp.hpl.jena.sparql.algebra.OpVisitor;
import com.hp.hpl.jena.sparql.algebra.OpVisitorBase;
@@ -140,9 +143,13 @@ public class TransformEliminateAssignments extends TransformCopy {
@Override
public Op transform(OpExtend opExtend, Op subOp) {
+ // No point tracking assignments if not in a projection as we can't
+ // possibly eliminate them without a projection to hide the fact that
+ // the assigned value is unnecessary or only used once
if (!this.tracker.insideProjection())
return super.transform(opExtend, subOp);
+ // Track the assignments for future reference
this.tracker.putAssignments(opExtend.getVarExprList());
// See if there are any assignments we can eliminate entirely i.e. those
@@ -165,21 +172,69 @@ public class TransformEliminateAssignments extends TransformCopy {
VarExprList modified = new VarExprList();
for (Var var : assignments.getVars()) {
+ // If an assignment is used more than once then it must be preserved
+ // for now
if (this.tracker.getUsageCount(var) > 1)
modified.add(var, assignments.getExpr(var));
}
+ // If all assignments are used more than once then there are no changes
+ // and we return null
if (modified.size() == assignments.size())
return null;
+
return modified;
}
@Override
public Op transform(OpOrder opOrder, Op subOp) {
- // TODO Auto-generated method stub
+ if (!this.isApplicable())
+ return super.transform(opOrder, subOp);
+
+ // See what vars are used in the sort conditions
+ Collection<Var> vars = new ArrayList<>();
+ for (SortCondition cond : opOrder.getConditions()) {
+ ExprVars.varsMentioned(vars, cond.getExpression());
+ }
+
+ // Are any of these vars single usage?
+ List<SortCondition> conditions = null;
+ for (Var var : vars) {
+ // Usage count will be 2 if we can eliminate the assignment
+ // First usage is when it is introduced by the assignment and the
+ // second is when it is used now in this filter
+ if (this.tracker.getUsageCount(var) == 2 && this.tracker.getAssignments().containsKey(var)) {
+ // Can go back and eliminate that assignment
+ subOp = Transformer.transform(
+ new TransformRemoveAssignment(var, this.tracker.getAssignments().get(var)), subOp);
+ // Replace the variable usage with the expression within the sort conditions
+ conditions = processConditions(opOrder.getConditions(), conditions, var);
+ this.tracker.getAssignments().remove(var);
+ }
+ }
+
+ // Create a new order if we've substituted any expressions
+ if (conditions != null) {
+ return new OpOrder(subOp, conditions);
+ }
+
return super.transform(opOrder, subOp);
}
+ private List<SortCondition> processConditions(List<SortCondition> baseConditions,
+ List<SortCondition> processedConditions, Var var) {
+ List<SortCondition> inputConditions = processedConditions != null ? processedConditions : baseConditions;
+ List<SortCondition> outputConditions = new ArrayList<>();
+
+ for (SortCondition cond : inputConditions) {
+ Expr e = cond.getExpression();
+ e = ExprTransformer.transform(new ExprTransformSubstitute(var, this.tracker.getAssignments().get(var)), e);
+ outputConditions.add(new SortCondition(e, cond.getDirection()));
+ }
+
+ return outputConditions;
+ }
+
@Override
public Op transform(OpTopN opTop, Op subOp) {
// TODO Auto-generated method stub
http://git-wip-us.apache.org/repos/asf/jena/blob/62dfb5aa/jena-arq/src/test/java/com/hp/hpl/jena/sparql/algebra/optimize/TestTransformEliminateAssignments.java
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diff --git a/jena-arq/src/test/java/com/hp/hpl/jena/sparql/algebra/optimize/TestTransformEliminateAssignments.java b/jena-arq/src/test/java/com/hp/hpl/jena/sparql/algebra/optimize/TestTransformEliminateAssignments.java
index ff8b65f..2f2ced9 100644
--- a/jena-arq/src/test/java/com/hp/hpl/jena/sparql/algebra/optimize/TestTransformEliminateAssignments.java
+++ b/jena-arq/src/test/java/com/hp/hpl/jena/sparql/algebra/optimize/TestTransformEliminateAssignments.java
@@ -92,6 +92,23 @@ public class TestTransformEliminateAssignments {
" (table unit)))");
//@formatter:on
}
+
+ @Test
+ public void eliminate_single_use_extend_03() {
+ // Assigned variable used only once can substitute expression for the
+ // later usage of the variable
+ // However we must be inside a projection as otherwise the assigned
+ // variable would be visible and we couldn't eliminate the assignment
+ //@formatter:off
+ test(StrUtils.strjoinNL("(project (?y)",
+ " (order (?x)",
+ " (extend (?x true)",
+ " (table unit))))"),
+ "(project (?y)",
+ " (order (true)",
+ " (table unit)))");
+ //@formatter:on
+ }
@Test
public void single_use_extend_unchanged_01() {