[Bioc-devel] BiocParallel and AnnotationDbi: database disk image is malformed

good question

some of the discussion on

http://sqlite.1065341.n5.nabble.com/Parallel-access-to-read-only-in-memory-database-td91814.html

seems relevant.

converting the relatively small annotation package content to pure R
read-only tables on the master before parallelizing
might be very simple?

On Fri, Jan 19, 2018 at 11:43 AM, Ludwig Geistlinger <
Ludwig.Geistlinger at sph.cuny.edu> wrote:

Hi,

Within a package I am developing, I would like to enable parallel probe to
gene mapping for a compendium of microarray datasets.

This accordingly makes use of annotation packages such as hgu133a.db,
which in turn connect to the SQLite database via AnnotationDbi.

When running in multi-core mode (i.e. using a MulticoreParam with
BiocParallel) using more than 2 cores, this causes the error:

database disk image is malformed


In a very similar problem:

https://support.bioconductor.org/p/38541/

Adi Tarca and Dan Tenenbaum identified and resolved this problem by
ensuring that each process has its own unique database connection, i.e.
AnnotationDbi is not loaded before sending the job to the workers.

This solution was easily realized as this analysis was carried out within
a script and not a package.

However, within my package, AnnotationDbi is loaded as a dependency of my
package's imports.

How to resolve this here?

I am not sure whether I perfectly understand the underlying mechanisms,
but is there a way to make my workers load their own version of
AnnotationDbi instead of using the one of the parent process?
Or am I supposed to unload all packages depending on AnnotationDbi, and
AnnotationDbi itself, before sending the job to the workers (and reload all
of them after the job has finished?)

Thanks a lot,
Ludwig



--
Dr. Ludwig Geistlinger
CUNY School of Public Health

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