public void rewriteGraphixASTNodes()

in asterix-graphix/src/main/java/org/apache/asterix/graphix/lang/rewrite/GraphixQueryRewriter.java [183:245]
46 lines of code
3 McCabe index (conditional complexity)

    public void rewriteGraphixASTNodes(GraphixRewritingContext graphixRewritingContext,
            IReturningStatement topStatement, boolean allowNonStoredUDFCalls) throws CompilationException {
        // Generate names for unnamed graph elements, projections in our SELECT CLAUSE, and keys in our GROUP BY.
        LOGGER.trace("Populating unknowns (both graph and non-graph) in our AST.");
        rewriteExpr(topStatement, new PopulateUnknownsVisitor(graphixRewritingContext));

        // Verify that variables are properly within scope.
        LOGGER.trace("Verifying that variables are unique and are properly scoped.");
        rewriteExpr(topStatement, new VariableScopingCheckVisitor(graphixRewritingContext));

        // Resolve all of our (Graphix, SQL++, and user-defined) function calls.
        LOGGER.trace("Resolving Graphix, SQL++, and user-defined function calls.");
        rewriteExpr(topStatement, new FunctionResolutionVisitor(graphixRewritingContext, allowNonStoredUDFCalls));

        // Rewrite implicit correlated vertex JOINs as explicit JOINs.
        LOGGER.trace("Rewriting correlated implicit vertex JOINs into explicit JOINs.");
        rewriteExpr(topStatement, new SubqueryVertexJoinVisitor(graphixRewritingContext));

        // Resolve our vertex labels, edge labels, and edge directions.
        LOGGER.trace("Performing label and edge direction resolution.");
        Map<GraphIdentifier, SchemaKnowledgeTable> knowledgeTableMap = new HashMap<>();
        Map<GraphIdentifier, PatternGroup> resolutionPatternMap = new HashMap<>();
        topStatement.accept(new PatternGraphGroupVisitor(resolutionPatternMap, graphixRewritingContext) {
            @Override
            public Expression visit(FromGraphClause fromGraphClause, ILangExpression arg) throws CompilationException {
                GraphIdentifier graphIdentifier = fromGraphClause.getGraphIdentifier(metadataProvider);
                SchemaKnowledgeTable schemaTable = new SchemaKnowledgeTable(fromGraphClause, graphixRewritingContext);
                knowledgeTableMap.put(graphIdentifier, schemaTable);
                return super.visit(fromGraphClause, arg);
            }
        }, null);
        for (Map.Entry<GraphIdentifier, PatternGroup> mapEntry : resolutionPatternMap.entrySet()) {
            SchemaKnowledgeTable knowledgeTable = knowledgeTableMap.get(mapEntry.getKey());
            new ExhaustiveSearchResolver(knowledgeTable).resolve(mapEntry.getValue());
        }

        // Fetch all relevant graph element declarations, using the element labels.
        LOGGER.trace("Fetching relevant edge and vertex bodies from our graph schema.");
        ElementLookupTable elementLookupTable = new ElementLookupTable();
        ElementLookupTableVisitor elementLookupTableVisitor =
                new ElementLookupTableVisitor(graphixRewritingContext, elementLookupTable, parserFactory);
        rewriteExpr(topStatement, elementLookupTableVisitor);
        for (GraphElementDeclaration graphElementDeclaration : elementLookupTable) {
            loadNormalizedGraphElement(graphixRewritingContext, graphElementDeclaration);
        }

        // Expand / enumerate vertex and edge patterns to snuff out all ambiguities.
        LOGGER.trace("Performing a canonicalization pass to expand or enumerate patterns.");
        BranchLookupTable branchLookupTable = new BranchLookupTable();
        QueryCanonicalizationVisitor queryCanonicalizationVisitor =
                new QueryCanonicalizationVisitor(branchLookupTable, graphixRewritingContext);
        rewriteExpr(topStatement, queryCanonicalizationVisitor);

        // Transform all graph AST nodes (i.e. perform the representation lowering).
        LOGGER.trace("Lowering the Graphix AST-specific nodes representation to a SQL++ representation.");
        GraphixLoweringVisitor graphixLoweringVisitor =
                new GraphixLoweringVisitor(graphixRewritingContext, elementLookupTable, branchLookupTable);
        rewriteExpr(topStatement, graphixLoweringVisitor);

        // Lower all of our Graphix function calls (and perform schema-enrichment).
        LOGGER.trace("Lowering the Graphix CALL-EXPR nodes to a pure SQL++ representation.");
        rewriteExpr(topStatement, new GraphixFunctionCallVisitor(graphixRewritingContext));
    }