如何重试错误语句？ [英] How to retry a statement on error?

问题描述

如果错误，我怎么能简单地告诉R重试一次语句？例如。我希望做一些像：

How can I simply tell R to retry a statement a few times if it errors? E.g. I was hoping to do something like:

tryCatch(dbGetQuery(...),           # Query database
    error = function(e) {
        if (is.locking.error(e))    # If database is momentarily locked
            retry(times = 3)        # retry dbGetQuery(...) 3 more times
        else {
            # Handle other errors
        }
    }
)

推荐答案

我通常将 try block放在一个循环中，
，当它不再失败或达到最大尝试次数。

I usually put the try block in a loop, and exit the loop when it no longer fails or the maximum number of attempts is reached.

some_function_that_may_fail <- function() {
  if( runif(1) < .5 ) stop()
  return(1)
}

r <- NULL
attempt <- 1
while( is.null(r) && attempt <= 3 ) {
  attempt <- attempt + 1
  try(
    r <- some_function_that_may_fail()
  )
} 

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