In particular:
* @@debug
deprecated since 5.5.37
* sr_YU locale
deprecated since 10.0.11
* "engine_condition_pushdown" in the @@optimizer_switch
deprecated since 10.1.1
* @@date_format, @@datetime_format, @@time_format, @@max_tmp_tables
deprecated since 10.1.2
* @@wsrep_causal_reads
deprecated since 10.1.3
* "parser" in mroonga table comment
deprecated since 10.2.11
Since wsrep_sync_wait & wsrep_causal_reads variables are related,
they are always kept in sync whenever one of them changes.
Same is tried on server start, where wsrep_sync_wait get updated
based on wsrep_causal_reads' value. But, since wsrep_causal_reads
is OFF by default, wsrep_sync_wait's value gets modified and loses
its WSREP_SYNC_WAIT_BEFORE_READ bit.
Fixed by syncing wsrep_sync_wait & wsrep_causal_reads values
individually on server start in mysqld_get_one_option() based
on command line arguments used.
