r shiny eventReactive with promises

Question

I am trying to use promises or some type of async in r shiny with mysql. I don't have a lot of users running this but as this scales up, I can see the need to use some type of promise? The following code is creating the query string in combination with dbGetQuery. If anyone has already answered this, please let me know.

tbl_selection <- eventReactive(input$go, {
  if ((input$Report) == "Report 1") {
    query <- paste0("select * from table where x=1")
  }
  else if ((input$Report) == "Report 2") { 
    query <- paste0("select * from table where x=2")
  }
  else if ((input$Report) == "Report 2") { 
    query <- paste0("select * from table where x=3")
  }

    dbGetQuery(con(), query)

})

Answer 1

Try this:

library(promises)
library(future)
plan(multisession)

myquery <- function(myinput){
  if (myinput == "Report 1") {
    query <- paste0("select * from table where x=1")
  }
  else if (myinput == "Report 2") { 
    query <- paste0("select * from table where x=2")
  }
  else if (myinput == "Report 3") { 
    query <- paste0("select * from table where x=3")
  }
  dbGetQuery(con(), query)
}


tbl_selection <- eventReactive(input$go, {
  future_promise({ 
    myquery(input$Report) 
  })
})