Question

我正在使用SpraklyR将csv读入spark中

schema <- structType(structField("TransTime", "array<timestamp>", TRUE),
                 structField("TransDay", "Date", TRUE))

 spark_read_csv(sc, filename, "path", infer_schema = FALSE, schema = schema)

但是得到：

Error: could not find function "structType"

如何使用spark_read_csv指定colunm类型？

提前致谢。

Answer 1

structType函数来自Scala的SparkAPI，在Sparklyr中指定必须在＆＃34;列中传递它的数据类型＆＃34;参数作为列表，假设我们有以下CSV（data.csv）：

name,birthdate,age,height
jader,1994-10-31,22,1.79
maria,1900-03-12,117,1.32

读取相应数据的功能是：

mycsv <- spark_read_csv(sc, "mydate", 
                          path =  "data.csv", 
                          memory = TRUE,
                          infer_schema = FALSE, #attention to this
                          columns = list(
                            name = "character",
                            birthdate = "date", #or character because needs date functions
                            age = "integer",
                            height = "double"))
# integer = "INTEGER"
# double = "REAL"
# character = "STRING"
# logical = "INTEGER"
# list = "BLOB"
# date = character = "STRING" # not sure

对于操作日期类型，您必须使用hive date functions，而不是R函数。

mycsv %>% mutate(birthyear = year(birthdate))

参考：https://spark.rstudio.com/articles/guides-dplyr.html#hive-functions

Answer 2

我们在官方sparklyr网站的一篇文章中有一个如何做到这一点的例子，这里是链接：http://spark.rstudio.com/example-s3.html#data_import

在Sparklyr中指定col类型（spark_read_csv）

2 个答案: