public Expression visit()

in asterix-graphix/src/main/java/org/apache/asterix/graphix/lang/rewrite/visitor/GraphixLoweringVisitor.java [196:244]
40 lines of code
10 McCabe index (conditional complexity)

    public Expression visit(FromGraphClause fromGraphClause, ILangExpression arg) throws CompilationException {
        // Perform an analysis pass over each element body. We need to determine what we can and can't inline.
        for (GraphElementDeclaration graphElementDeclaration : elementLookupTable) {
            ElementBodyAnalysisVisitor elementBodyAnalysisVisitor = new ElementBodyAnalysisVisitor();
            IElementIdentifier elementIdentifier = graphElementDeclaration.getIdentifier();
            graphElementDeclaration.getNormalizedBody().accept(elementBodyAnalysisVisitor, null);
            analysisContextMap.put(elementIdentifier, elementBodyAnalysisVisitor.getElementBodyAnalysisContext());
        }
        LoweringEnvironment workingEnvironment = environmentStack.getLast();

        // TODO (GLENN): Perform smarter analysis to determine when a vertex / edge is inlineable w/ LEFT-MATCH.
        Stream<MatchClause> matchClauseStream = fromGraphClause.getMatchClauses().stream();
        workingEnvironment.setInlineLegal(matchClauseStream.noneMatch(c -> c.getMatchType() == MatchType.LEFTOUTER));

        // Lower our MATCH-CLAUSEs. We should be working with canonical-ized patterns.
        for (MatchClause matchClause : fromGraphClause.getMatchClauses()) {
            if (matchClause.getMatchType() == MatchType.LEFTOUTER) {
                workingEnvironment.beginLeftMatch();
            }
            for (PathPatternExpr pathPatternExpr : matchClause.getPathExpressions()) {
                for (EdgePatternExpr edgePatternExpr : pathPatternExpr.getEdgeExpressions()) {
                    edgePatternExpr.accept(this, fromGraphClause);
                }
                for (VertexPatternExpr vertexPatternExpr : pathPatternExpr.getVertexExpressions()) {
                    VariableExpr vertexVariableExpr = vertexPatternExpr.getVariableExpr();
                    if (aliasLookupTable.getIterationAlias(vertexVariableExpr) != null) {
                        continue;
                    }
                    workingEnvironment.acceptAction(actionFactory.buildDanglingVertexAction(vertexPatternExpr));
                }
                workingEnvironment.acceptAction(actionFactory.buildPathPatternAction(pathPatternExpr));
            }
            if (matchClause.getMatchType() == MatchType.LEFTOUTER) {
                workingEnvironment.endLeftMatch();
            }
        }
        workingEnvironment.acceptAction(actionFactory.buildMatchSemanticAction(fromGraphClause));

        // Finalize our lowering by moving our lower list to our environment.
        workingEnvironment.endLowering(fromGraphClause);

        // Add our correlate clauses, if any, to our tail FROM-TERM.
        if (!fromGraphClause.getCorrelateClauses().isEmpty()) {
            LowerListClause lowerClause = (LowerListClause) fromGraphClause.getLowerClause();
            ClauseCollection clauseCollection = lowerClause.getClauseCollection();
            fromGraphClause.getCorrelateClauses().forEach(clauseCollection::addUserDefinedCorrelateClause);
        }
        return null;
    }