This is partial cherry-pick from commit
b3f300b9.  In the QD, the distributed
transactions become visible at the same time as the corresponding
local ones, so we can rely on the local XIDs. This is true because the
modification of local procarray and globalXactArray are protected by
lock and hence a atomic operation during transaction commit.

We have seen many situations where catalog queries run very slow on QD
and potential reason is checking distributed logs. Process local
distributed log cache fall short for this usecase as most of XIDs are
unique and hence get frequent cache misses. Shared memory cache falls
short as only caches 8 pages and many times need many more pages to be
cached to be effective.
Co-authored-by: NHubert Zhang <hzhang@pivotal.io>
Co-authored-by: NGang Xiong <gangx@vmware.com>