Transactions

node-postgres does not have any special apis for dealing with transactions; just use sql.

Below are two examples of how to run transactions. Generally you'll probably use some kind of flow control library or abstract this behind a function or something. I use nothing but node & pg to keep the examples as clear as possible.

Here is how you would do a transaction using the client pool:

varpg=require('pg');varrollback=function(client,done){client.query('ROLLBACK',function(err){//if there was a problem rolling back the query//something is seriously messed up. Return the error//to the done function to close & remove this client from//the pool. If you leave a client in the pool with an unaborted//transaction __very bad things__ will happen.returndone(err);});};pg.connect(function(err,client,done){if(err)throwerr;client.query('BEGIN',function(err){if(err)returnrollback(client,done);//as long as we do not call the `done` callback we can do //whatever we want...the client is ours until we call `done`//on the flip side, if you do call `done` before either COMMIT or ROLLBACK//what you are doing is returning a client back to the pool while it //is in the middle of a transaction. This is __very, very bad__.process.nextTick(function(){vartext='INSERT INTO account(money) VALUES($1) WHERE id = $1';client.query(text,[100,1],function(err){if(err)returnrollback(client,done);client.query(text,[-100,2],function(err){if(err)returnrollback(client,done);client.query('COMMIT',done);});});});});});

Here is how you would do a transaction using a single instance of a client:

varClient=require('pg').Client;varclient=newClient(/*your connection info goes here*/);client.connect();varrollback=function(client){//terminating a client connection will//automatically rollback any uncommitted transactions//so while it's not technically mandatory to call//ROLLBACK it is cleaner and more correctclient.query('ROLLBACK',function(){client.end();});};client.query('BEGIN',function(err,result){if(err)returnrollback(client);client.query('INSERT INTO account(money) VALUES(100) WHERE id = $1',[1],function(err,result){if(err)returnrollback(client);client.query('INSERT INTO account(money) VALUES(-100) WHERE id = $1',[2],function(err,result){if(err)returnrollback(client);//disconnect after successful commitclient.query('COMMIT',client.end.bind(client));});});});