add a better clarification on how sysvar changes "propagate" (#5562) #5641
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Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com>
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This is an automated cherry-pick of #5562
What is changed, added or deleted? (Required)
The sysvar docs imply that the 2 second delay is propagation to other servers. This is not the case, there is no propagation at all, because the table is stored in TiKV. The delay is the global values cache, and thus it affects the issuing server as well.
This affects all versions, but master will hopefully have a fix soon so I'll create a separate PR to document the different semantics.
Which TiDB version(s) do your changes apply to? (Required)
What is the related PR or file link(s)?
For GA releases it is pingcap/tidb#22808
(I will leave the issue open until master is fixed)
Do your changes match any of the following descriptions?