How to force Nextflow process to recalculate and ignore cache in resumed workflow

Question

I have a series of processes in nextflow pipeline, employing multiple heavy computing steps and database (SQL) insertion/fetch. I need to insert certain (intermediate) process results to the DB and fetch them later for further processing (within the same pipeline). In the most simplified form it will be something like:

• process1 (fetch data from DB)
• process2 (analyze process1.out)
• process3 (inserts process2.out to DB)

The problem is, that when any values are changed in the DB, output from process1 is still cached (when using -resume flag), so changes in DB are not reflected here at all.

Is there any way to force reprocessing process1 while using -resume and ignore cache?
So far, I was manually deleting respective work folder, or adding dummy line to process1, but that is extremely ineffective solution.

Thanks for any help here.

Answer 1

Result caching is enable by default, but this feature can be disabled using the cache directive by setting the value to false. For example:

process process1 {

    cache false

    ...
}

Not sure if we have the full picture here, but updating a database with some set of process results just to fetch them again later on seems wasteful. Or maybe I've just misunderstood. I would instead try to separate the heavy computational work (hours) from the database transactions (minutes) if at all possible. Note that if you need to make per process database transactions, you might be able to achieve this using the beforeScript and afterScript directives (which can be enabled/disabled using a nextflow.config profile, for example). For example, a beforeScript could be used to create a database object that is updated (using an afterScript) once the process has completed. Since both of these scripts are run from inside the workDir, you could use the basename of the current/working directory (i.e. the task UUID) as a key.