script runner built-in script "Copy custom field values" always times out

[Andy Keyworth]

We're cleaning up our JIRA custom fields (in JIRA 7, on our own server). Part of this is copying values from two separate fields into one amalgamated field of the same type. We need to move values from the old field(s) into the new, and I'm trying to use the script runner "Copy custom field values" built-in script. But every time I try to do so, it returns a timeout error: "Error timeout: No Stack Trace available". The preview says there it identifies 1969 issues, and that doesn't seem exorbitant.

[Geoff Wilson]

From my experience with using these type of Scriptrunner built-in scripts, there is a limit to how many issues it allows you to process at once. I will try to update this answer if I can remember the exact limit, but otherwise I believe it is either 500, 600, or 1000.  As such, you will need to create multiple filters to whittle down your data set of 1969 issues, and then run each of these filters through the same Copy Custom Field Value execution plan (i.e. choose Filter 1, set the source Field ID, set the Target Field ID, Run.  Then repeat with Filter 2). 

To note, there is a default limit of 1000 in JIRA for how many issues you can even view or export at once, but this can be changed.  See this page: https://confluence.atlassian.com/jirakb/exporting-a-filter-result-containing-more-than-1000-issues-191500982.html