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box.schema.func.create()
Create a function. The created function can be used in different usage scenarios, for example, in :ref:`field or tuple constraints <index-constraints>` or :ref:`functional indexes <box_space-index_func>`.
Using the :ref:`body <function_options_body>` option, you can make a function *persistent*. In this case, the function is "persistent" because its definition is stored in a snapshot (the :ref:`box.space._func <box_space-func>` system space) and can be recovered if the server restarts.
Parameters
a name of the function, which should conform to the :ref:`rules for object names <app_server-names>`
see :ref:`function_options <func_create_function_options>`
return
nil
:ref:`box.schema.user.grant() <box_schema-user_grant>` can be used to allow the specified user or role to execute the created function.
**Example 1: a non-persistent Lua function**
The example below shows how to create a non-persistent Lua function:
box.schema.func.create('calculate')
box.schema.func.create('calculate', {if_not_exists = false})
box.schema.func.create('calculate', {setuid = false})
box.schema.func.create('calculate', {language = 'LUA'})
**Example 2: a persistent Lua function**
The example below shows how to create a persistent Lua function, show its definition using ``box.func.{func-name}``, and call this function using ``box.func.{func-name}:call([parameters])``:
tarantool> lua_code = [[function(a, b) return a + b end]]
tarantool> box.schema.func.create('sum', {body = lua_code})

tarantool> box.func.sum
---
- is_sandboxed: false
is_deterministic: false
id: 2
setuid: false
body: function(a, b) return a + b end
name: sum
language: LUA
...

tarantool> box.func.sum:call({1, 2})
---
- 3
...
To call functions using ``net.box``, use :ref:`net_box:call() <net_box-call>`.
**Example 3: a persistent SQL expression used in a tuple constraint**
The code snippet below defines a function that checks a tuple's data using the SQL expression:
box.schema.func.create('check_person', {
language = 'SQL_EXPR',
is_deterministic = true,
body = [["age" > 21 AND "name" != 'Admin']]
})
Then, this function is used to create a tuple :ref:`constraint <index-constraints>`:
local customers = box.schema.space.create('customers', { constraint = 'check_person' })
customers:format({
{ name = 'id', type = 'number' },
{ name = 'name', type = 'string' },
{ name = 'age', type = 'number' },
})
customers:create_index('primary', { parts = { 1 } })
On an attempt to insert a tuple that doesn't meet the required criteria, an error is raised:
customers:insert { 2, "Bob", 18 }
-- error: Check constraint 'check_person' failed for tuple
function_options
A table containing options passed to the :ref:`box.schema.func.create(func-name [, function_options]) <box_schema-func_create_with-body>` function.
Specify whether there should be no error if the function already exists.
Type: boolean
Default: ``false``
Make Tarantool treat the function's caller as the function's creator, with full privileges. Note that ``setuid`` works only over :ref:`binary ports <admin-security>`. ``setuid`` doesn't work if you invoke a function using the :ref:`admin console <admin-security>` or inside a Lua script.
Specify the function language. The possible values are:

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testing_project / Documentation: reference/reference_lua/box_schema/func_create — English

tarantool> lua_code = [[function(a, b) return a + b end]]
tarantool> box.schema.func.create('sum', {body = lua_code})

tarantool> box.func.sum
---
- is_sandboxed: false
is_deterministic: false
id: 2
setuid: false
body: function(a, b) return a + b end
name: sum
language: LUA
...

tarantool> box.func.sum:call({1, 2})
---
- 3
...
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