pg - PostgreSQL connector for Tarantool

Getting Started

Prerequisites

• Tarantool 1.6.5+ with header files (tarantool && tarantool-dev packages)
• PostgreSQL 8.1+ header files (libpq-dev package)

Installation

Clone repository and then build it using CMake:

git clone https://github.com/tarantool/pg.git
cd pg && cmake . -DCMAKE_BUILD_TYPE=RelWithDebugInfo
make
make install

You can also use LuaRocks:

luarocks install https://raw.githubusercontent.com/tarantool/pg/master/pg-scm-1.rockspec --local

See tarantool/rocks for LuaRocks configuration details.

Usage

local pg = require('pg')
local conn = pg.connect({host = localhost, user = 'user', pass = 'pass', db = 'db'})
local tuples = conn:execute("SELECT $1 AS a, 'xx' AS b", 42)
conn:begin()
conn:execute("INSERT INTO test VALUES(1, 2, 3)")
conn:commit()

API Documentation

conn = pg:connect(opts = {})

Connect to a database.

Options:

• host - a hostname to connect
• port - a port numner to connect
• user - username
• pass or password - a password
• db - a database name
• conn_string (mutual exclusive with host, port, user, pass, db) - PostgreSQL connection string

Returns:

• connection ~= nil on success
• error(reason) on error

conn:execute(statement, ...)

Execute a statement with arguments in the current transaction.

Returns:

• { { { column1 = value, column2 = value }, ... }, { {column1 = value, ... }, ...}, ...}, true on success
• error(reason) on error

Example:

tarantool> conn:execute("SELECT $1 AS a, 'xx' AS b", 42)
---
- - - a: 42
      b: xx
    ...

conn:begin()

Begin a transaction.

Returns: true

conn:commit()

Commit current transaction.

Returns: true

conn:rollback()

Rollback current transaction.

Returns: true

conn:ping()

Execute a dummy statement to check that connection is alive.

Returns:

• true on success
• false on failure

pool = pg.pool_create(opts = {})

Create a connection pool with count of size established connections.

Options:

• host - hostname to connect to
• port - port number to connect to
• user - username
• password - password
• db - database name
• size - count of connections in pool

Returns

• pool ~=nil on success
• error(reason) on error

conn = pool:get()

Get a connection from pool. Reset connection before returning it. If connection is broken then it will be reestablished. If there is no free connections then calling fiber will sleep until another fiber returns some connection to pool.

Returns:

• conn ~= nil

pool:put(conn)

Return a connection to connection pool.

Options

• conn - a connection

Comments

All calls to connections api will be serialized, so it should to be safe to use one connection from some count of fibers. But you should understand, that you can have some unwanted behavior across db calls, for example if another fiber 'injects' some sql between two your calls.

See Also

• Tests
• Tarantool
• Tarantool Rocks