PUT /rest/api/2/issue/{issueIdOrKey} method is loading all possible fields ids with all values into memory.

In particular this endpoint loads all possible versions for each version field creating thousands of VersionBean.

This data is completely not needed in this resource.

Effects

1. Loading all this data consumes a lot of memory for 64k versions this is taking up to 100MB of RAM.
2. Creating REST beans for all those values is slow and as an effect editing issues trough REST is slow. 

This bug is essentially in IssueInputParametersAssembler class in 

private Set<String> getValidFieldsForEdit(Issue issue) { EditMetaFieldBeanBuilder builder = new EditMetaFieldBeanBuilder(fieldLayoutManager, issue.getProjectObject(), issue, issue.getIssueType(), jiraAuthenticationContext.getLoggedInUser(), versionBeanFactory, velocityRequestContextFactory, contextUriInfo, baseUrls, fieldScreenRendererFactory, fieldManager, issueManager); Set<String> strings = new HashSet<>(); strings.add(IssueFieldConstants.COMMENT); strings.addAll(builder.build().keySet()); return strings; }

We get only keys from EditMetaFieldBeanBuilder

builder.build().keySet()

We should instead add method

builder.buildKeys()

WORKAROUND

Remove the field that has many values from appropriate screen.