Tales of a developer

I've added search and trim to my  expiring records  module in Erlang. This started out as an  in-memory  key/value store, that I then migrated over to  using Mnesia  and eventually to a  replicated Mnesia  table. The  fetch/1  function is already doing a simple query, with  match_object . Result = mnesia : match_object ( expiring_records , # record { key = Key , value = '_' , expires_at = '_' }, read ) The three parameters there are the name of the table -  expiring_records , the matching pattern and the lock type (read lock). The  fetch/1  function looks up the key as it was added to the table with  store/3 . If the key is a tuple, we can also do a partial match: Result = mnesia : match_object ( expiring_records , # record { key = { '_' , " bongo " }, value = '_' , expires_at = '_' }, read ) I've added a  search/1  function the module that takes in a matching pattern and ...

I'm still working on my  expiring records  module in Erlang (see  here  and  here  for my previous posts on this). Previously, I had started using Mnesia, but only a RAM based table. I've now switched it over to a replicated disc based table. That was easy enough, but it took a while to figure out how to do, nonetheless. I had assumed that simply adding ... { disc_copies , [ node ()]} ... to the arguments to  mnesia:create_table  would be enough. This resulted in an error: { app_test , init_per_testcase , {{ badmatch , { aborted , { bad_type , expiring_records , disc_copies , nonode@nohost }}}, ... After some head-scratching and lots of Googling I realized that I was missing a call to  mnesia:create_schema  to allow it to create disc based tables. My tests for this module are done with  common_test  so I set up a per suite initializat...

Continuing with my  expiring records  module (see  my previous blog ), I've now switched it over to using  Mnesia , rather than a dictionary object stored in the state of my  gen_server  instance. It is still not a truly global, cross-node key/value store for expiring records, but it is getting there. I wanted to focus first on getting my tests to pass again with a RAM based table on one node. I just need to tweak the values passed in when creating the Mnesia table, I think, to make this work with a disc based table, replicated across nodes. Currently the table is created like this: prepare_table () -> case catch mnesia : table_info ( expiring_records , attributes ) of { 'EXIT' , _ } -> % % Table does not exist - create it erlang : display ( " Creating table " ), mnesia : create_table ( expiring_records , [ { attributes , record_info ( fields , record )}, ...