Elixir ETS key pattern matching

Question

I am using ETS to cached a database schema from postegress using ecto here are those examples:

table = :ets.new(:cache_name,[:set, :protected])

and include those registry:

:ets.insert(table,{:first_table,{1}})

:ets.insert(table,{:first_table,{5}})

:ets.insert(table,{:second_table,{1}})

but the second one replace the first one, for that reason i concat the table name and the id to get a unique key :ets.insert(table,{:first_table1,{1}}) for these registry, but at the moment that i want the first registry for the first table i have a problem because i contain the same key for the second and it retreive two registry:

:ets.match_object(table,{:"_",{1}})

how can i specify to ETS that if the key contains the table_name retreive these registry?

Dogbert Dogbert · Accepted Answer · 2017-05-17T20:36:21

I don't think you can match part of the atom's name with :ets.match_object. I'd suggest using a tuple of table name and id as the key if you want a lookup based on both table and id as well as only table:

table = :ets.new(:cache_name, [:set, :protected])

:ets.insert(table, {{:first_table, 1}, {1}})
:ets.insert(table, {{:first_table, 2}, {5}})
:ets.insert(table, {{:second_table, 1}, {1}})

# Get table = :first_table, id = 1
IO.inspect :ets.lookup(table, {:first_table, 1})
# Get table = :first_table and any id
IO.inspect :ets.match_object(table, {{:first_table, :_}, :_})

Output:

[{{:first_table, 1}, {1}}]
[{{:first_table, 1}, {1}}, {{:first_table, 2}, {5}}]

Elixir ETS key pattern matching

1 Answers