session: fix show variable
result of tidb_enable_window_function
after upgrade (#13866)
#14131
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cherry-pick #13866 to release-3.0
…
What problem does this PR solve?
tidb_enable_window_function
will display as1
inshow variables
's result after upgrade from old version, but realtidb_enable_window_function
value will keep 0 due to keep syntax compatibility, on another hand, new cluster can safe use1
as default value.What is changed and how it works?
when upgrade from old version, insert a default 0 value if no exists record in
GLOBAL_VARIABLES
Check List
Tests
Code changes
Side effects
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Release note
show variable
result oftidb_enable_window_function
after upgradeThis change is