> I'm trying to get the postgresql interface working. I can't seem to
> find too much on details on how to use it. In looking through the
> code, I see erlydb:start(psql) does not exist for a match, so I get a
> driver_not_supported error. I see I can manually do the
> application:start for this, but should I?
The erlydb support for Postgres is terrible, bad enough that I've
stopped my attempt to migrate to it from mnesia and am going back. The
in-between state is a frustrating one, and is the primary reason that
development of my application has stagnated. Error messages are non-
existent or misleading, and the usual result of doing something,
anything, wrong is a hang on starting psql or on the first erlydb
access.
That said, here's how I got it to work. I have a wrotit.app (whose
contents aren't important), and then I start wrotit with
application:start(wrotit), and the following:
------- psql.app -------
{application,
psql, [
{description, "psql $Rev$"},
{vsn, "0.0.2"},
{registered, [psql_sup]},
{applications, [kernel, stdlib]},
{mod, {psql, []}},
{env, [{erlydb_psql, {"localhost",
5432,
"wrotit", "password",
"wrotit_db"}},
{pools, [{erlydb_psql, 5}]}]}
]}.
------- wrotit.erl -------
-module(wrotit).
-behavior(application).
-export([start/2, start/0,
stop/1,
compile/0, compile/1]).
-compile(export_all).
start() -> start([],[]).
start(_Type, _Args) ->
%% compile first (if nothing else, this at least loads in my
%% modules)
compile(),
%% bring up yaws (doesn't appear in my supervisor hierarchy)
wrotit_init:start_yaws(),
%% bring up psql, required by erlydb_psql
start_psql_driver(),
%% my main supervisor will be returned
wrotit_supervisor:start_link().
start_psql_driver() ->
case is_loaded(psql) of
true ->
ok;
false ->
application:start(psql)
end.
is_loaded(App) ->
lists:keymember(App,1,application:which_applications()).
stop(_State) ->
ok=yaws:stop(),
ok=psql:stop(),
ok.
compile() ->
compile([]).
compile(ExtraOptions) ->
%% read in wrotit.app
application:load(wrotit),
start_psql_driver(),
Options=[native,
debug_info,
{erlydb_driver,psql},
{auto_compile,wrotit_config:dev_mode()},
{i,wrotit_config:yaws_include()},
{allow_unsafe_statements,true},
{last_compile_time,auto}] ++ ExtraOptions,
code:add_paths([wrotit_config:yaws_ebin(),
wrotit_config:erlyweb_ebin(),
wrotit_config:plists_ebin()]),
erlyweb:compile(wrotit_config:appdir(),Options).
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