public Expression visit()

in asterix-graphix/src/main/java/org/apache/asterix/graphix/lang/rewrite/visitor/SubqueryVertexJoinVisitor.java [86:146]
49 lines of code
12 McCabe index (conditional complexity)

    public Expression visit(MatchClause matchClause, ILangExpression arg) throws CompilationException {
        GraphIdentifier workingGraphIdentifier = graphIdentifierStack.peek();
        ScopeChecker workingScopeChecker = vertexScopeMap.get(workingGraphIdentifier);
        Scope precedingScope = workingScopeChecker.getPrecedingScope();
        Scope currentScope = workingScopeChecker.getCurrentScope();

        Map<VariableExpr, VariableExpr> remappedVariables = new HashMap<>();
        for (PathPatternExpr pathExpression : matchClause.getPathExpressions()) {
            for (VertexPatternExpr vertexExpression : pathExpression.getVertexExpressions()) {
                VariableExpr vertexVariable = vertexExpression.getVariableExpr();
                VarIdentifier vertexName = vertexVariable.getVar();
                if (precedingScope == null || precedingScope.getParentScope() == null) {
                    // We are in a top-level FROM-GRAPH-CLAUSE. Add this variable to our current scope.
                    currentScope.addSymbolToScope(vertexName);

                } else if (currentScope.findLocalSymbol(vertexName.getValue()) == null
                        && currentScope.findSymbol(vertexName.getValue()) != null) {
                    // We have a nested Graphix query, and we have found a vertex that references an outer vertex.
                    SelectBlock parentSelectBlock = (SelectBlock) arg;

                    // Replace the current vertex variable with a copy.
                    VariableExpr newVariable = graphixRewritingContext.getGraphixVariableCopy(vertexVariable);
                    vertexExpression.setVariableExpr(newVariable);
                    vertexExpression.getVariableExpr().setSourceLocation(vertexVariable.getSourceLocation());
                    vertexExpression.addHint(new SubqueryVertexJoinAnnotation(vertexVariable));
                    remappedVariables.put(vertexVariable, newVariable);

                    // JOIN our copy with the parent vertex variable.
                    List<Expression> joinArgs = List.of(vertexVariable, newVariable);
                    OperatorExpr joinExpr = new OperatorExpr(joinArgs, List.of(OperatorType.EQ), false);
                    parentSelectBlock.getLetWhereList().add(new WhereClause(joinExpr));

                } else if (currentScope.findLocalSymbol(vertexName.getValue()) == null) {
                    // We have a nested Graphix query that does not correlate with an outer query.
                    currentScope.addSymbolToScope(vertexName);

                } else if (remappedVariables.containsKey(vertexVariable)) {
                    // We have replaced this variable already. Update the reference.
                    VariableExpr remappedVertexVariable = remappedVariables.get(vertexVariable);
                    vertexExpression.setVariableExpr(graphixDeepCopyVisitor.visit(remappedVertexVariable, null));
                    vertexExpression.getVariableExpr().setSourceLocation(vertexVariable.getSourceLocation());
                    vertexExpression.addHint(new SubqueryVertexJoinAnnotation(vertexVariable));
                }
            }
            for (EdgePatternExpr edgeExpression : pathExpression.getEdgeExpressions()) {
                VertexPatternExpr leftVertex = edgeExpression.getLeftVertex();
                VertexPatternExpr rightVertex = edgeExpression.getRightVertex();
                if (remappedVariables.containsKey(leftVertex.getVariableExpr())) {
                    VariableExpr leftVariableRemap = remappedVariables.get(leftVertex.getVariableExpr());
                    leftVertex.setVariableExpr(graphixDeepCopyVisitor.visit(leftVariableRemap, null));
                    leftVertex.addHint(new SubqueryVertexJoinAnnotation(leftVariableRemap));
                }
                if (remappedVariables.containsKey(rightVertex.getVariableExpr())) {
                    VariableExpr rightVariableRemap = remappedVariables.get(rightVertex.getVariableExpr());
                    rightVertex.setVariableExpr(graphixDeepCopyVisitor.visit(rightVariableRemap, null));
                    rightVertex.addHint(new SubqueryVertexJoinAnnotation(rightVariableRemap));
                }
            }
        }
        return null;
    }