immediate argument to dbSendQuery()

[krlmlr]

Adds params and immediate arguments to dbSendQuery() (and, via dots, dbSendStatement(), dbGetQuery() and dbExecute()). Uses SQLExecDirect if immediate is TRUE; in this case, params are necessarily ignored.

Currently a very quick-and-dirty proof of concept, will refine when we agree on the API.

Part of r-dbi/DBI#268.

Closes #163. Closes #127.

library(DBI)

mssql_con <- function() {
  DBI::dbConnect(
    odbc::odbc(),
    Driver = "SQL Server Driver",
    ...,
    TDS_Version = 7.4,
    Port = 1433
  )
}

con <- mssql_con()

dbExecute(con, "SELECT 1 AS a INTO #test", immediate = TRUE)
#> [1] 1
dbGetQuery(con, "SELECT * FROM #test")
#>   a
#> 1 1
try(dbExecute(con, "SELECT 1 AS a INTO #test", immediate = TRUE))
#> Error in new_result(connection@ptr, statement, immediate) : 
#>   nanodbc/nanodbc.cpp:1526: 42S01: [FreeTDS][SQL Server]There is already an object named '#test' in the database.
dbGetQuery(con, "SELECT * FROM #test", immediate = TRUE)
#>   a
#> 1 1

^{Created on 2019-04-16 by the reprex package (v0.2.1.9000)}

[krlmlr]

Should dbGetQuery() and dbExecute() always use the "direct" API if no parameters are given?

[jimhester]

No, I think they should not use it unless it is requested.

[jimhester]

Otherwise I think it looks good, thanks!

[krlmlr]

Thanks. I'll tweak and remove the "WIP" when ready.

[jimhester]

Ok, just ping me when you do so I don't miss it!

[jimhester]

Setting this to request changes until you have time to work on it @krlmlr

[jimhester]

Ok I finished this off, thanks!