有：采购记录。使用sparkyr:：sdf\u sql将spark表读入tbl\u spark。
太大，无法使用dbi:：dbgetquery（10^8行和30+列）输出到驱动程序节点上的local r data.frame
个人出行日期产品价格130-01-2021适用$1.50130-01-2021加纳$0.89127-01-2021范围$1.00127-01-2021适用$1.20229-01-2021适用$2.00229-01-2021适用$1.20228-01-2021适用$2.50
需求：独特买家表，按最近旅行筛选。
个人出行日期产品价格130-01-2021适用$1.50229-01-2021价格$2.00

spark_version <- "3.1.0"
sc <- spark_connect(method = "databricks")

五次尝试
1.

Fruit_buyers <- Fruit_purchases %>% distinct(Person_id, .keep_all=TRUE)

# Error : Can only find distinct value of specified columns if .keep_all is FALSE

Fruit_buyers <- Fruit_purchases %>% 
      arrange(Person_id, desc(Trip_date)) %>%
      group_by(Person_id) %>% 
      slice(1)

# Error in slice_.tbl_spark(.data, .dots = compat_as_lazy_dots(...)) : Slice is not supported in this version of sparklyr

Fruit_buyers <- Fruit_purchases %>% 
       arrange(Person_id, desc(Trip_date)) %>%
       group_by(Person_id) %>% 
       slice_head()

# Error in slice_head(.) : could not find function "slice_head"

Fruit_buyers <- Fruit_purchases %>% 
  arrange(Person_id, desc(Trip_date)) %>%
  group_by(Person_id) %>% 
  top_n(1)

# Databricks log: Selecting by Person_id

# Then later error when printing:

# org.apache.spark.sql.AnalysisException: Undefined function: 'top_n_rank'. This function is neither a registered temporary function nor a permanent function registered in the database 'default'

Fruit_buyers <- Fruit_purchases %>% 
   arrange(Person_id, desc(Trip_date)) %>%
   group_by(Person_id) %>% 
   summarise_all(first) %>%

# Error in nth(x, 1L, order_by = order_by, default = default) :  object 'Product' not found

6.分组后索引

Fruit_buyers <- Fruit_purchases %>% 
      arrange(Person_id, desc(Trip_date)) %>%
      group_by(Person_id) %>% 
      mutate(RowN = row_number()) %>%
      filter(RowN == 1)

# Error : java.lang.IllegalArgumentException: invalid method count for object 44/java.lang.Class fields 0 selected 0

不能做总结所有（分钟），因为这混淆了价格列。
SparkyR是否支持postgresql及其独特的语法？
进一步的问题：可以收集多少数据？驱动程序节点的大小是唯一的限制吗

R version 3.6.3 (2020-02-29)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 18.04.5 LTS

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/openblas/libblas.so.3
LAPACK: /usr/lib/x86_64-linux-gnu/libopenblasp-r0.2.20.so

locale:
 [1] LC_CTYPE=C.UTF-8       LC_NUMERIC=C           LC_TIME=C.UTF-8       
 [4] LC_COLLATE=C.UTF-8     LC_MONETARY=C.UTF-8    LC_MESSAGES=C.UTF-8   
 [7] LC_PAPER=C.UTF-8       LC_NAME=C              LC_ADDRESS=C          
[10] LC_TELEPHONE=C         LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C   

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] dplyr_0.8.5    sparklyr_1.4.0