docs: private static boolean checkPureColumnIndex(Index index, int aggCol, List<AbstractExpression> filterExprs) {
  
          boolean found = false;
  
          // all left child of filterExprs must be of type TupleValueExpression in equality comparison
          for (AbstractExpression expr : filterExprs) {
              if (expr.getExpressionType() != ExpressionType.COMPARE_EQUAL) {
                  return false;
              }
              if (!(expr.getLeft() instanceof TupleValueExpression)) {
                  return false;
              }
              if (((TupleValueExpression)expr.getLeft()).getColumnIndex() == aggCol) {
                  found = true;
              }
          }
  
          if (found) {
              return true;
          }
          if (index.getColumns().size() > filterExprs.size()) {
              List<ColumnRef> indexedColRefs = CatalogUtil.getSortedCatalogItems(index.getColumns(), "index");
  
              if (indexedColRefs.get(filterExprs.size()).getColumn().getIndex() == aggCol) {
                  return true;
              }
          }
  
          return false;
      }