CreateQuery null_lc_set_index (children 3)
 Identifier null_lc_set_index
 Columns definition (children 2)
  ExpressionList (children 3)
   ColumnDeclaration timestamp (children 1)
    DataType DateTime
   ColumnDeclaration action (children 1)
    DataType LowCardinality (children 1)
     ExpressionList (children 1)
      DataType Nullable (children 1)
       ExpressionList (children 1)
        DataType String
   ColumnDeclaration user (children 1)
    DataType LowCardinality (children 1)
     ExpressionList (children 1)
      DataType Nullable (children 1)
       ExpressionList (children 1)
        DataType String
  ExpressionList (children 1)
   Index (children 2)
    Identifier user
    Function set (children 1)
     ExpressionList (children 1)
      Literal UInt64_0
 Storage definition (children 4)
  Function MergeTree
  Function toYYYYMMDD (children 1)
   ExpressionList (children 1)
    Identifier timestamp
  Function tuple (children 1)
   ExpressionList (children 3)
    Identifier timestamp
    Identifier action
    Function cityHash64 (children 1)
     ExpressionList (children 1)
      Identifier user
  Set
