I have a resource that has the following fields with regexes:
attribute :cnpj_basico, :string do
public? true
allow_nil? false
constraints min_length: 8, max_length: 8, match: ~r/^[A-Za-z0-9]{8}$/
end
attribute :cnpj_sufixo, :string do
public? true
allow_nil? false
constraints min_length: 6, max_length: 6, match: ~r/^\d{6}$/
end
attribute :cnpj_formatado, :string do
public? true
allow_nil? false
constraints min_length: 18, max_length: 18, match: ~r/^\d{2}\.\d{3}\.\d{3}\/\d{4}-\d{2}$/
end
I need to bulk insert millions of rows into the database using this resource.
I noticed that casting the resource would have a major slowdown if the match constraints are in place.
Here are the most expensive calls with match enabled using eprof:
# CALLS % TIME ĀµS/CALL
Total 3676 100.0 2155 0.59
...
:crypto.strong_rand_bytes_nif/1 1 0.79 17 17.00
Ecto.Type.cast_fun/1 13 0.84 18 1.38
Ash.Changeset.force_change_attribute/3 10 1.07 23 2.30
Enum."-map/2-lists^map/1-1-"/2 80 1.16 25 0.31
:lists.member/2 47 1.16 25 0.53
:lists.keyfind/3 40 1.16 25 0.63
:ets.match_object/2 4 1.30 28 7.00
:re.import/1 495 24.41 526 1.06
Core.Cnpj.Estabelecimento.persisted/0 41 38.61 832 20.29
And here are the most expensive ones if I remove the match constraint
# CALLS % TIME ĀµS/CALL
Total 3160 100. 592 0.19
Spark.Dsl.Extension.persisted!/3 43 1.69 10 0.23
Ash.Changeset.do_change_attribute/4 7 1.86 11 1.57
:erlang.module_loaded/1 30 1.86 11 0.37
anonymous fn/1 in Ash.Changeset.expand_upsert_fields/2 37 2.20 13 0.35
Enum."-map/2-lists^map/1-1-"/2 80 2.36 14 0.18
:crypto.strong_rand_bytes_nif/1 1 2.53 15 15.00
Ash.Changeset.force_change_attribute/3 10 2.70 16 1.60
:erlang.binary_to_atom/2 8 2.70 16 2.00
:ets.match_object/2 4 4.22 25 6.25
As you can see, the call went from 2155 ĀµS to 592 ĀµS.
This is even more expressive when processing the data in bulk, my times when from (10_000 chunks) ~6 seconds to 0.3~0.5 seconds.
So, is there some way to optimize this checks in Ash.Changeset calls during casting?
If not, is there some way for me to disable the regex check during bulk insertion so I can make it faster?
Iāve wanted a generic regex transpiration library for a while, thought of writing it myself. Something to take an elixir regex and transpire it to match spec, js, and PostgreSQL especially. (naturally allowing that not all regexes can be translated that way).
that is very surprising. Iām wondering if we may be applying the regex more than once for case where its an attribute constraint 
.
