LRU cache for compiling expressions into functions.
Using CompilerCache, it is easy to create custom expressions that perform well.
Instead of relying on using Code.eval_quoted, the CompilerCache
system compiles given ASTs into modules.
The compilation cache has a fixed maximum size, and uses a fixed pool of module names as not to exhaust the BEAM vm's atom table.
Creating a compilation cache is as simple as use CompilerCache and
implementing the create_ast/1 function:
defmodule MyExpressionCache do
use CompilerCache
def create_ast(expr) do
{:ok, ast} = Code.string_to_quoted(expr)
{ast, []}
end
endThe create_ast/2 function must return an {ast, opts} tuple. The opts are the same as those given to Code.eval_quoted/3.
This cache can then be called like this:
{:ok, _} = MyExpressionCache.start_link()
iex> MyExpressionCache.execute("1 + 1", nil)
2
iex> MyExpressionCache.execute("2 * input", 3)
6The input argument is always called 'input'. There is just one input
argument - use a tuple and pattern matching to use multiple
arguments. To use a different variable name, use the :input_name
config option in the use statement.
After N cache misses (default: 1, so the second time the same expression is called), expressions are cached into a module on the background by the compiler process. This speeds up consecutive executions considerable (~10x speedups are not unheard of).
Cached expressions (modules) are unloaded when they have not been used after max_ttl milliseconds (default: 1000).
The number of cached expressions can be limited by setting the cache_size option, which defaults to 10_000.
Full documentation: https://hexdocs.pm/compiler_cache/
The package is available on hex.pm and can be installed like this:
- Add
compiler_cacheto your list of dependencies inmix.exs:
```elixir
def deps do
[{:compiler_cache, "~> 1.0"}]
end
```
- Ensure
compiler_cacheis started before your application:
```elixir
def application do
[applications: [:compiler_cache]]
end
```
-
Implement your compiler by using
use CompilerCacheand implementingcreate_ast/1, then put it in your supervisor tree:worker(MyExpressionCache, [])