如何在sparklyr的dplyr实现返回的列表中循环显示不同的列结果？

Question

鉴于spark studio here提供的闪亮示例

library(sparklyr)
packageVersion("sparklyr")
#‘0.8.4’
sc <- spark_connect(master = "local")
#* Using Spark: 2.3.0
install.packages(c("nycflights13", "Lahman"))
library(dplyr)
flights_tbl <- copy_to(sc, nycflights13::flights, "flights")
src_tbls(sc)
#[1] "flights"

试图循环不同的值，

carriers <- flights_tbl %>% filter(dep_delay >= 1000) %>% dplyr::select(carrier) %>% dplyr::distinct()
> carriers
# Source:   lazy query [?? x 1]
# Database: spark_connection
  carrier
  <chr>  
1 MQ     
2 HA     
3 AA     
> typeof(carriers)
[1] "list"

像这样：

 for (carrier in carriers){
      print(carrier)
    }

返回此意外结果：

> for (carrier in carriers){
+   print(carrier)
+ }
spark connection master=local[4] app=sparklyr local=TRUE

From: flights
<Table: flights>
-> filter()
   - ~dep_delay >= 1000
-> select()
   - ~carrier
-> distinct()

而不是简单地：

 MQ     
 HA     
 AA  

如何循环不同的值？

Answer 1

好吧，显然首先应该“收集”火花结果（参见qazxsw poi）

here