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Getting Started With Lua UDFs

Currently, User-Defined Functions are written in Lua. Lua is a powerful, fast, lightweight, embeddable scripting language. To learn more about Lua, see About Lua.

If this is your first foray into Lua programming, then we suggest the following material:

Lua Version​

Aerospike currently supports Lua 5.1.4.

Lua Restrictions​

Aerospike supports the full Lua programming language, with a few exceptions.

Globals are restricted​

  • Global variables are not allowed.
  • Global functions can only be called by Aerospike Server, and cannot be called by other Lua functions.
  • To call a custom Lua function from another Lua function, the called function must be declared as a "local" function. For example, external function sum() can call local function add(), provided it is defined as local.
    local function add(a,b)
          return a + b
    end

    function sum(a,b)
          return add(a,b)
    end

Restricted modules and functions​

  • coroutines - Lua functions can call each other provided they are "forward declared" before their actual use. In this example, we forward-declare fun_B() and then we can use it inside the body of fun_B(). We don't have to forward-declare fun_A() in this example because it is declared first.
    local fun_B

    local fun_A( foo )
        fun_B( foo.bar )
    end

    local fun_B( bar )
        fun_A( bar.foo )
    end
  • debug module – Not enabled due to not being able to support the debugging features in Lua.
  • os.exit() – Not enabled because it didn't make sense for a Lua script to cause the database to process to exit.