An Erlang port driver for bridging an Erlang app and a q process, implemented with asyncronous tasks to allow parallel execution. Built on top of kx's C bindings (c.o).

Works for Mac OSX and Linux, developed on OS X Mavericks and CentOS 6.4, running on a production kdb+ instance that writes more than 7 GB of data daily.

gen_q implements q's full list of rich data types and provides access to arbitrary q function calls via IPC. With gen_q, you can feed your tickerplant directly from an Erlang application, and you can run queries to pull data back out again.

Add the following to your Erlang app's rebar.config.

{gen_q, ".*", {git, "git@github.com:republicwireless-open/gen_q.git", {tag, "1.0"}}}

Before compiling, if your target q process is version 3 or higher, you must edit gen_q's rebar.config and add -DKXVER=3 to the CFLAGS. Then, compile and start your app.

Start the port driver with the following command.

> {ok, _Pid} = q:start_link().
{ok,<0.1401.0>}

Open an IPC handle to your q process.

%                   Host         Port  Credentials          Timeout
> {ok, H} = q:hopen("localhost", 5000, "username:password", 10000).
{ok,18}

Evaluate a q expression from Erlang.

> q:eval(H, "2+2").
{ok,{long,4}}

Notice that results returned from the q module include the data type from the q result. This gets more interesting with some of q's more esoteric types.

> q:eval(H, ".z.p").
{ok,{timestamp,478041037666903000}}

You can also call functions.

> q:apply(H, sum, {list, float}, [1,2,3]).
{ok,{float,6.0}}

And close your connection.

> q:hclose(H).
ok

If you're targeting a q instance version 3 or higher, you must add -DKXVER=3 to your CFLAGS in gen_q's rebar.config.

If you're compiling for Darwin (Mac OS X), there are a couple caveats:

• A 32bit version of libgcc_s.1 is required. The rebar.config includes the path /opt/local/lib/gcc48 in an attempt to locate the file. Edit as needed.
• On Darwin, gen_q does not compile within the rebar dependency tree. Change directory to deps/gen_q and run make from there.

Run the unit tests with

make test

Note that due to an unknown issue with port drivers running inside a rebar eunit task, rebar may SEGFAULT after all the tests have run successfully. This is being tracked in the open issues.