private Scope analyzeFrom(QuerySpecification node, Optional<Scope> scope) {
      if (node.getFrom().isPresent()) {
        return process(node.getFrom().get(), scope);
      }

      Scope result = createScope(scope);
      analysis.setImplicitFromScope(node, result);
      return result;
    }
Visitor context represents local query scope (if exists). The invariant is that the local query
scopes hierarchy should always have outer query scope (if provided) as ancestor.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/analyzer/StatementAnalyzer.java