1 files changed, 12 insertions, 1 deletions

diff --git a/subprojects/interpreter/src/main/java/tools/refinery/interpreter/matchers/psystem/rewriters/PBodyCopier.java b/subprojects/interpreter/src/main/java/tools/refinery/interpreter/matchers/psystem/rewriters/PBodyCopier.java
index 99350185..1e580599 100644
--- a/subprojects/interpreter/src/main/java/tools/refinery/interpreter/matchers/psystem/rewriters/PBodyCopier.java
+++ b/subprojects/interpreter/src/main/java/tools/refinery/interpreter/matchers/psystem/rewriters/PBodyCopier.java
@@ -137,7 +137,9 @@ public class PBodyCopier extends AbstractRewriterTraceSource {
         } else if (constraint instanceof PatternMatchCounter) {
             copyPatternMatchCounterConstraint((PatternMatchCounter) constraint);
         } else if (constraint instanceof AggregatorConstraint) {
-            copyAggregatorConstraint((AggregatorConstraint) constraint);
+                        copyAggregatorConstraint((AggregatorConstraint) constraint);
+                } else if (constraint instanceof LeftJoinConstraint leftJoinConstraint) {
+                        copyLeftJoinConstraint((LeftJoinConstraint) constraint);
         } else if (constraint instanceof ExpressionEvaluation) {
             copyExpressionEvaluationConstraint((ExpressionEvaluation) constraint);
         } else {
@@ -256,6 +258,15 @@ public class PBodyCopier extends AbstractRewriterTraceSource {
                 constraint.getReferredQuery(), mappedResultVariable, constraint.getAggregatedColumn()));
     }
 
+        protected void copyLeftJoinConstraint(LeftJoinConstraint constraint) {
+                PVariable[] mappedVariables = extractMappedVariables(constraint);
+                PVariable mappedResultVariable = variableMapping.get(constraint.getResultVariable());
+                Tuple variablesTuple = Tuples.flatTupleOf((Object[]) mappedVariables);
+                addTrace(constraint, new LeftJoinConstraint(body, variablesTuple,
+                                constraint.getReferredQuery(), mappedResultVariable, constraint.getOptionalColumn(),
+                                constraint.getDefaultValue()));
+        }
+
     protected void copyExpressionEvaluationConstraint(ExpressionEvaluation expressionEvaluation) {
         PVariable mappedOutputVariable = variableMapping.get(expressionEvaluation.getOutputVariable());
         addTrace(expressionEvaluation, new ExpressionEvaluation(body,