public GraphTraversal generateTraversal()

in sql-gremlin/src/main/java/org/twilmes/sql/gremlin/adapter/converter/ast/nodes/select/GremlinSqlSelectSingle.java [98:154]
47 lines of code
10 McCabe index (conditional complexity)

    public GraphTraversal<?, ?> generateTraversal() throws SQLException {
        if (sqlSelect.getSelectList() == null) {
            throw SqlGremlinError.create(SqlGremlinError.SELECT_NO_LIST);
        }

        final GremlinSqlOperator gremlinSqlOperator =
                GremlinSqlFactory.createOperator(sqlBasicCall.getOperator(), sqlBasicCall.getOperandList());
        if (!(gremlinSqlOperator instanceof GremlinSqlAsOperator)) {
            throw SqlGremlinError.create(SqlGremlinError.UNEXPECTED_FROM_FORMAT);
        }
        final List<GremlinSqlNode> gremlinSqlOperands = GremlinSqlFactory.createNodeList(sqlBasicCall.getOperandList());
        final List<GremlinSqlIdentifier> gremlinSqlIdentifiers = new ArrayList<>();
        for (final GremlinSqlNode gremlinSqlOperand : gremlinSqlOperands) {
            if (!(gremlinSqlOperand instanceof GremlinSqlIdentifier)) {
                throw SqlGremlinError.create(SqlGremlinError.UNEXPECTED_FROM_FORMAT);
            }
            gremlinSqlIdentifiers.add((GremlinSqlIdentifier) gremlinSqlOperand);
        }

        GraphTraversal<?, ?> graphTraversal = null;
        try {
            graphTraversal =
                    SqlTraversalEngine.generateInitialSql(gremlinSqlIdentifiers, sqlMetadata, g);
            final String label = sqlMetadata.getActualTableName(gremlinSqlIdentifiers.get(0).getName(1));

            // This function basically generates the latter parts of the traversal, by doing this it prepares all the
            // renamed labels in the metadata so that queries like 'SELECT foo AS bar FROM baz ORDER BY bar'
            // can properly recognize that bar=>foo.
            // __.__() is passed in as an anonymous traversal that will be discarded.
            generateDataRetrieval(gremlinSqlIdentifiers, __.__());

            // Generate actual traversal.
            applyWhere(graphTraversal);
            applyGroupBy(graphTraversal, label);
            applySelectValues(graphTraversal);
            applyOrderBy(graphTraversal, label);
            applyHaving(graphTraversal);
            sqlMetadata.setIsDoneFilters(true);
            generateDataRetrieval(gremlinSqlIdentifiers, graphTraversal);

            if (sqlMetadata.getRenamedColumns() == null) {
                throw SqlGremlinError.create(SqlGremlinError.COLUMN_RENAME_LIST_EMPTY);
            }
            if (sqlMetadata.getTables().size() != 1) {
                throw SqlGremlinError.create(SqlGremlinError.NO_TRAVERSAL_TABLE);
            }
            return graphTraversal;
        } catch (final SQLException e) {
            if (graphTraversal != null) {
                try {
                    graphTraversal.close();
                } catch (final Exception ignored) {
                }
            }
            throw e;
        }
    }