CreateQuery agg_over_nullable (children 3)
 Identifier agg_over_nullable
 Columns definition (children 1)
  ExpressionList (children 4)
   ColumnDeclaration partition (children 1)
    DataType Date
   ColumnDeclaration timestamp (children 1)
    DataType DateTime
   ColumnDeclaration user_id (children 1)
    DataType Nullable (children 1)
     ExpressionList (children 1)
      DataType UInt32
   ColumnDeclaration description (children 1)
    DataType Nullable (children 1)
     ExpressionList (children 1)
      DataType String
 Storage definition (children 1)
  Function MergeTree (children 1)
   ExpressionList (children 3)
    Identifier partition
    Identifier timestamp
    Literal UInt64_8192