[ANN] LuaPSQL (was: Lua and Postgres)
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- Subject: [ANN] LuaPSQL (was: Lua and Postgres)
- From: Luis Carvalho <lexcarvalho@...>
- Date: 2011年1月15日 22:28:19 -0500
<snip>
> 1) Is LuaSQL the best way to interface between Lua and Postgres?
I've had a libpq binding for some time, but haven't released it yet since I've
had no time to put together some decent documentation. Given the recent need
and demand, I just decided to finally publish it (MIT license) by adding some
minor documentation.
So, I'm glad to announce the availability of LuaPSQL:
http://code.google.com/p/luapsql
Please check attached README file from the package.
> 2) Is it necessary to go through LuaRocks? Is there a better way?
LuaRocks is the standard way, but the package contains a Makefile.
> 3) What is the procedure to install the Lua/Postgres interface?
The usual 'luarocks make' or 'luarocks install' when the rockspec hits the
repository.
Cheers,
Luis
--
Computers are useless. They can only give you answers.
-- Pablo Picasso
--
Luis Carvalho (Kozure)
lua -e 'print((("lexcarvalho@NO.gmail.SPAM.com"):gsub("(%u+%.)","")))'
LuaPSQL
=======
This is LuaPSQL, a binding of PostgreSQL's client library, libpq, for Lua.
This module is specific to PostgreSQL and offers more functionality when
compared to the generic LuaSQL bindings:
* Binary types as equivalent as possible to Lua types (moreover, check
"registered types" below)
* Asynchronous connections and query executions
* Parametrizable statements
* Prepared statements
The routines are, however, *low*-level methods, most of them simply wrapping
their C counterparts. For this reason, a more detailed documentation is not
included and the user can refer to PostgreSQL's documentation on libpq for
details -- check the chapter entitled "libpq - C library". This binding is
fairly complete, with the sole exception of function associated with the COPY
command.
Here's a simple example:
local psql = require "psql"
-- check result set
local function checkset (conn, rset)
local status = rset:status()
assert(status == "PGRES_COMMAND_OK" or status == "PGRES_TUPLES_OK",
conn:error())
return rset
end
-- connect
local conn = psql.connect "dbname=test"
assert(conn:status(), conn:error())
-- create and populate table
checkset(conn, conn:exec"CREATE TABLE x (i int, f double precision)")
local plan = assert(conn:prepare("INSERT INTO x VALUES (1,ドル 2ドル)"))
for i = 1, 10 do
checkset(conn, plan:exec(i, math.sin(math.pi / i)))
end
-- list table
local rset = checkset(conn, conn:exec"SELECT * FROM x")
local f = rset:fields()
for i, t in rset:rows() do
for k in pairs(f) do
print(i, k, t[k])
end
end
-- wrap up
checkset(conn, conn:exec"DROP TABLE x")
conn:finish()
More usage examples can be found in the "test" and "etc" folders.
Registered types
----------------
It is possible to register specific types in LuaPSQL using:
metatable = psql.register(oid [, metatable])
If `metatable` is not provided a new table will be created. psql.register sets
field `__oid` to the provided `oid` parameter (to get the oid of a certain
type, issue "select 'typename'::regtype::oid" in psql.)
The metatable for your registered type should contain two fields, `__send` and
`__recv` that specify how values are translated from Lua to PostgreSQL and
vice-versa, respectively:
bytea_str = objmt.__send(obj)
obj = objmt.__recv(bytea_str, fmod)
For examples, check `pqtype.c`.
Installation
------------
The installation should be straightforward as LuaPSQL uses Luarocks. However,
if you want to run the tests in the `test` folder you will also need
`pqtype.so`; to compile it, modify the rockspec file according to the comments
in it.