问题（bug？）与MonetDB.R和dbWriteTable与csvdump = TRUE

Question

We are managing to write 1.7 M rows in 30s or so (on a MacBook Pro) using R and MonetDB.R within a shiny application:

dbWriteTable(conn, tableName, Dt,overwrite=TRUE, csvdump=TRUE)

As we understand the MonetDB.R code saves first in a /tmp folder the table in a csv format, then is loaded onto the MonetDB database with COPY INTO

We have just tried on a centos server and RStudio Server and we got an access right error on the temporary folder in /tmp .

We resolved the problem with the classic

chmod -R 777 /tmp

But it seems we have to do it again if we run this part of the app within shiny hence it does not look a scalable solution.

Would it be possible to get a more stable & scalable solution?

(also, this feature was documented in MonetDB 0.94 but it does not appear anywhere in the 0.95 document on CRAN - can we safely assume that this is a typo and the feature is going to stay?)

Answer 1

MonetDB.R uses R's tempfile() to create the temporary CSV file. tempfile in turn calls tempdir to get a temporary directory. You can control the location of this directory through the environment variable TMPDIR and others. See ?tempdir for details.

eg

$ TMPDIR=/tmp/foo R -e "print(tempfile())"
[1] "/tmp/bar/Rtmp7UKG0k/file1173e13a4477c"

$ TMPDIR=/tmp/bar R -e "print(tempfile())"
[1] "/tmp/foo/RtmpPxx76t/file1174a409c06a2"

With regards to your other question, the csvdump feature is going to remain, since MonetDB is quite fast at bulk CSV loading.