lua-pgsql is a PostgreSQL client for Lua. It is compatible with Lua 5.2.3(or above) and based on the PostgreSQL C API.

Build

install Lua from repo and then

make

or use the environment variable LUADIR to specify the Lua source you want to use

LUADIR=/path/to/lua make

Lua APIs

First you need to use pgsql = require('luapgsql') to import a table named pgsql(or any other valid name).

• client, errmsg = pgsql.newclient(dbarg)

  • Attempts to establish a connection to a PostgreSQL server specified by dbarg. If successfully executed, a valid PostgreSQL client client, plus a nil for errmsg, are returned; otherwise client will be nil and an error message errmsg is returned. See luapgsql-demo.lua for more details about dbarg.

• errmsg = client:ping()

  • Checks whether the connection to the server is working. If the connection has gone down and auto-reconnect is enabled an attempt to reconnect is made. If the connection is down and auto-reconnect is disabled, an error message errmsg is returned.

• errmsg = client:setcharset(charset)

  • Sets the default character set to be charset for the current connection. nil is returned if successfully executed, otherwise an error message errmsg is returned.

• result, errmsg = client:execute(sqlstr)

  • Executes a SQL statement sqlstr. If successfully executed, a result containing all information, and a nil for errmsg, are returned; otherwise the result will be nil, and the error message errmsg tells what happened.

• size = result:size()

  • Returns the number of record(s) in the result. nil is returned if error occurs.

• fieldnamelist = result:fieldnamelist()

  • Returns the fieldname list for the result. nil is returned if error occurs.

• result:recordlist()

  • Returns an iteration closure function which can be used in the for ... in form. nil is returned if error occurs. Each record returned by the iterator function is an array containing values corresponding to the fieldname list which is the result of result:fieldnamelist().

See luapgsql-demo.lua for more details.

C Library

lua-pgsql can also be integrated with C/C++ programs for executing Lua scripts. See host.c for how to import it into C/C++ environment.

FAQ

• If you try to run luapgsql-demo.lua with the following command:

  $ lua luapgsql-demo.lua

  but encounter an error message like this:

  lua dynamic libraries not enabled; check your Lua installation

  which means you need to re-compile Lua with extra arguments to enable loading dynamic libraries. For example, in Linux systems:

  $ make posix MYCFLAGS="-DLUA_USE_DLOPEN -fPIC" MYLIBS=-ldl

• If there is an error message like this:

  multiple Lua VMs detected

  you may re-compile the Lua interpreter with option -Wl,-E.

Have fun!