asterix-graphix/src/main/java/org/apache/asterix/graphix/lang/rewrite/lower/EnvironmentActionFactory.java [240:256]:
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                final Expression filterExpr = vertexPatternExpr.getFilterExpr();
                if (filterExpr != null) {
                    loweringEnvironment.acceptAction(buildFilterExprAction(filterExpr, vertexVar, iterationVar));
                }

                // Bind our intermediate (join) variable and vertex variable.
                loweringEnvironment.acceptTransformer(lowerList -> {
                    VariableExpr iterationVarCopy1 = graphixDeepCopyVisitor.visit(iterationVar, null);
                    VariableExpr iterationVarCopy2 = graphixDeepCopyVisitor.visit(iterationVar, null);
                    VariableExpr intermediateVarCopy = graphixDeepCopyVisitor.visit(intermediateVar, null);
                    LetClause nonRepresentativeBinding = new LetClause(intermediateVarCopy, iterationVarCopy1);
                    lowerList.addNonRepresentativeClause(nonRepresentativeBinding);
                    lowerList.addVertexBinding(vertexVar, iterationVarCopy2);
                });
                aliasLookupTable.addIterationAlias(vertexVar, iterationVar);
                aliasLookupTable.addJoinAlias(vertexVar, intermediateVar);
            };
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asterix-graphix/src/main/java/org/apache/asterix/graphix/lang/rewrite/lower/EnvironmentActionFactory.java [592:609]:
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                    final Expression filterExpr = vertexPatternExpr.getFilterExpr();
                    if (filterExpr != null) {
                        loweringEnvironment.acceptAction(buildFilterExprAction(filterExpr, vertexVar, iterationVar));
                    }

                    // Bind our intermediate (join) variable and vertex variable.
                    loweringEnvironment.acceptTransformer(lowerList -> {
                        VariableExpr iterationVarCopy1 = graphixDeepCopyVisitor.visit(iterationVar, null);
                        VariableExpr iterationVarCopy2 = graphixDeepCopyVisitor.visit(iterationVar, null);
                        VariableExpr intermediateVarCopy = graphixDeepCopyVisitor.visit(intermediateVar, null);
                        LetClause nonRepresentativeBinding = new LetClause(intermediateVarCopy, iterationVarCopy1);
                        lowerList.addNonRepresentativeClause(nonRepresentativeBinding);
                        lowerList.addVertexBinding(vertexVar, iterationVarCopy2);
                    });
                    aliasLookupTable.addIterationAlias(vertexVar, iterationVar);
                    aliasLookupTable.addJoinAlias(vertexVar, intermediateVar);
                }
            };
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