R help - May 2011 - tryCatch?

I would like to do inserts into a database table, but do updates in the fairly
rare cases in which the inserts fail. I thought tryCatch might be the way to do
it, but I honestly do not understand the help file for tryCatch at all.

I thought something like this might work:
for (i in seq(along = tbl$key)) {
    tryCatch(sqlSave(pg, tbl[i, ], "tbl", append = TRUE, rownames =
FALSE),
        if (fails) do {sqlUpdate(pg, tbl[i, ], index = "key")})
}

This obviously isn't the correct syntax, but could tryCatch do this if I got
the syntax right? And any tips on what the right syntax would be?

Mikkel

Start with try(): you may find it easier to understand.

if(inherits(try(<call1>), "try-error")) <call2>

so in your case

if(inherits(try(sqlSave(pg, tbl[i, ], "tbl", append = TRUE,
                         rownames = FALSE))))
     sqlUpdate(pg, tbl[i, ], index = "key")

or some such.

On Wed, 4 May 2011, Mikkel Grum wrote:
> I would like to do inserts into a database table, but do updates in the
fairly rare cases in which the inserts fail. I thought tryCatch might be the way
to do it, but I honestly do not understand the help file for tryCatch at all.
>
> I thought something like this might work:
> for (i in seq(along = tbl$key)) {
>    tryCatch(sqlSave(pg, tbl[i, ], "tbl", append = TRUE, rownames
= FALSE),
>        if (fails) do {sqlUpdate(pg, tbl[i, ], index = "key")})
> }
>
> This obviously isn't the correct syntax, but could tryCatch do this if
I got the syntax right? And any tips on what the right syntax would be?
>
> Mikkel
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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