Add thread-local caching to SectionManager

closing per stephens comments

Tested on trunk with full regression test on Section Info using an expanded version of the test plan on Confluence.

Pls merge to 2-5-x.

Hi Josh,

Please could you review the changes committed for this issue.

r45572

This commit also changes the implementation of getSectionEnrollments(String userUid, String courseUuid) to use the new authz method authzGroupService.getAuthzUserGroupIds, so for 2-5-x and 2-4-x this introduces a dependency on (commits to authz). This actually does not introduce any performance advantages for the Student Overview case, but may have advantages for other uses.

With the changes in this issue, each authzgroup is now only read once. The number of SAKAI_REALM queries generated for the student overview page is now therefore 5 x number of sections in the site (e.g. 100 sections = 500 queries to render the page).

Not as good as it could be, but better than it was.

Committed section_info_threadlocal_cached.diff from parent issue in r45570.

Testing with 10 sections in a local trunk build shows that queries to SAKAI_REALM* tables are reduced from 304 to 151.

Still not ideal, but some improvement is better than no improvement.