reference: update documents about pessimistic transaction (#1854)#2206

Merged

ran-huang merged 4 commits into

pingcap:release-3.1from

sre-bot:release-3.1-965012863103

Apr 19, 2020

Commits on Apr 8, 2020

cherry pick #1854 to release-3.1

ran-huang
authored and
sre-bot
committed

Commits on Apr 9, 2020

Merge branch 'release-3.1' into release-3.1-965012863103
lilin90
authored

Commits on Apr 10, 2020

resolve conflict
ran-huang
committed

Commits on Apr 19, 2020

Merge branch 'release-3.1' into release-3.1-965012863103
ran-huang
authored