When we need to add/remove or change LIMIT, INTERVAL, AUTO we have to recreate partitioning from scratch. Such operations should be done fast. To remove options like LIMIT or INTERVAL one should write:
alter table t1 partition by system_time;
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The command checks whether it is new or existing SYSTEM_TIME partitioning. And in the case of new it behaves as CREATE would do: adds default number of partitions (2). If SYSTEM_TIME partitioning already existed it just changes its options: removes unspecified ones and adds/changes those specified explicitly. In case when partitions list was supplied it behaves as usual: does full repartitioning.
Examples:
create or replace table t1 (x int) with system versioning
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partition by system_time limit 100 partitions 4;
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# Change LIMIT
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alter table t1 partition by system_time limit 33;
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# Remove LIMIT
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alter table t1 partition by system_time;
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# This does full repartitioning
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alter table t1 partition by system_time limit 33 partitions 4;
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# This does data copy as pruning will require records in correct partitions
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alter table t1 partition by system_time interval 1 hour
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starts '2000-01-01 00:00:00';
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# But this works fast, LIMIT will apply to DML commands
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alter table t1 partition by system_time limit 33;
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Bug
Major
MDEV-19903 Setup default partitions for system versioning
