space_object:on_replace()

object space_object¶

space_object:on_replace([trigger-function[, old-trigger-function]])¶

Create a “replace trigger”. The trigger-function will be executed whenever a replace() or insert() or update() or upsert() or delete() happens to a tuple in <space-name>.

Parameters:	trigger-function (function) – function which will become the trigger function; see Example 2 below for details about trigger function parameters old-trigger-function (function) – existing trigger function which will be replaced by trigger-function
Return:	nil or function pointer

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

If both parameters are omitted, then the response is a list of existing trigger functions.

If it is necessary to know whether the trigger activation happened due to replication or on a specific connection type, the function can refer to box.session.type().

Details about trigger characteristics are in the triggers section.

See also space_object:before_replace().

Example 1:

tarantool> x = 0
         > function f ()
         >   x = x + 1
         > end
tarantool> box.space.my_space_name:on_replace(f)

Example 2:

The trigger-function can have up to four parameters:

• (tuple) old value which has the contents before the request started,
• (tuple) new value which has the contents after the request ended,
• (string) space name,
• (string) type of request which is INSERT, DELETE, UPDATE, or REPLACE.

For example, the following code causes nil and INSERT to be printed when the insert request is processed and causes [1, 'Hi'] and DELETE to be printed when the delete request is processed:

box.schema.space.create('space_1')
box.space.space_1:create_index('space_1_index',{})
function on_replace_function (old, new, s, op) print(old) print(op) end
box.space.space_1:on_replace(on_replace_function)
box.space.space_1:insert{1,'Hi'}
box.space.space_1:delete{1}

Example 3:

The following series of requests will create a space, create an index, create a function which increments a counter, create a trigger, do two inserts, drop the space, and display the counter value - which is 2, because the function is executed once after each insert.

tarantool> s = box.schema.space.create('space53')
tarantool> s:create_index('primary', {parts = {{field = 1, type = 'unsigned'}}})
tarantool> function replace_trigger()
         >   replace_counter = replace_counter + 1
         > end
tarantool> s:on_replace(replace_trigger)
tarantool> replace_counter = 0
tarantool> t = s:insert{1, 'First replace'}
tarantool> t = s:insert{2, 'Second replace'}
tarantool> s:drop()
tarantool> replace_counter

Note

As everything executed inside triggers is already in a transaction, you shouldn’t use in trigger-functions for on_replace and before_replace

• transactions,
• yield-operations (explicit or not),
• actions that are not allowed to be used in transactions (see rule #2).

Example:

tarantool> box.space.test:on_replace(fiber.yield)
tarantool> box.space.test:replace{1, 2, 3}
2020-02-02 21:22:03.073 [73185] main/102/init.lua txn.c:532 E> ER_TRANSACTION_YIELD: Transaction has been aborted by a fiber yield
---
- error: Transaction has been aborted by a fiber yield
...