box.ctl.on_schema_init() | Tarantool


box.ctl.on_schema_init(trigger-function[, old-trigger-function])

Create a “schema_init trigger”. The trigger-function will be executed when box.cfg{} happens for the first time. That is, the schema_init trigger is called before the server’s configuration and recovery begins, and therefore box.ctl.on_schema_init must be called before box.cfg is called.

  • trigger-function (function) – function which will become the trigger function
  • old-trigger-function (function) – existing trigger function which will be replaced by trigger-function

nil or function pointer

If the parameters are (nil, old-trigger-function), then the old trigger is deleted.

A common use is: make a schema_init trigger function which creates a before_replace trigger function on a system space. Thus, since system spaces are created when the server starts, the before_replace triggers will be activated for each tuple in each system space. For example, such a trigger could change the storage engine of a given space, or make a given space replica-local while a replica is being bootstrapped. Making such a change after box.cfg is not reliable because other connections might use the database before the change is made.

Details about trigger characteristics are in the triggers section.


Suppose that, before the server is fully up and ready for connections, you want to make sure that the engine of space space_name is vinyl. So you want to make a trigger that will be activated when a tuple is inserted in the _space system space. In this case you could end up with a master that has space-name with engine='memtx' and a replica that has space_name with engine='vinyl', with the same contents.

function function_for_before_replace(old, new)
  if old == nil and new ~= nil and new[3] == 'space_name' and new[4] ~= 'vinyl' then
    return new:update{{'=', 4, 'vinyl'}}


box.cfg{replication='master_uri', ...}
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