How to use Cayley with a Postgres backend?

Question

As per this Github issue, the Postgres backend feature for the Cayley graph database is implemented. However, currently there aren't examples in the docs, and I couldn't figure it out by reading the code. Could someone help?

Edit

To start playing with Cayley, we can load data that comes with the source with the following command:

./cayley load --config=cayley.cfg.overview --quads=data/30kmoviedata.nq.gz

I tried two variations of the cayley.cfg.overview file:

{
    "database": "sql",
    "db_path": "localhost:5432",
    "read_only": false
}

and

{
    "database": "sql",
    "db_path": "/var/lib/postgresql/9.4/main/cayley",
    "read_only": false
}

The first one being analogous to the one used with mongo (5432 being the port at which the postgres server is listening). As for the second one, I have no clue of what I'm doing there :D.

In any case, when I use the ./cayley load --config=cayley.cfg.overview --quads=data/30kmoviedata.nq.gz command I get the following error (varying only the value of db_path):

Couldn't open database at localhost:5432: 
&errors.errorString{s:"missing \"=\" after \"127.0.0.1:5432\" in connection 
info string\""}
E1117 21:09:18.300033 16689 cayley.go:277] missing "=" after "localhost:5432" 
in connection info string"

Can you post what you have now and provide more specific information about what error you're facing? It might be more constructive to pose each specific error as a question since configuring a system can be pretty open ended (ie you're stuck on error A and resolve it to find error B and then get error C and so on). — evanmcdonnal, Nov 18 '15 at 00:30
Can you try using your `localhost:5432` config but with `"database":"mongo"` ? In most examples the value is `leveldb` in the docs one of the values is `mongo`, however there is no `sql` value as far as I can tell. In between my other work I'll track down that file (`caylay.go`) and see what's going on there because the error would indicate there should be a trailing equals but I don't see any examples that have anything remotely similar (not like it's a sql connection string and has credentials ect after that). — evanmcdonnal, Nov 18 '15 at 02:05
Found part of what I'm looking for. You're failing in here, the call to `Load` returns that error https://github.com/google/cayley/blob/master/cmd/cayley/cayley.go#L209 — evanmcdonnal, Nov 18 '15 at 02:08
@evanmcdonnal using config with `"database": "mongo"` if for using with a mongodb backend. There is a `sql` value for `database` (see [source](https://github.com/google/cayley/blob/master/graph/sql/quadstore.go)), however it isn't documented, and I haven't been able to figure it out yet. — Marcus Vinícius Monteiro, Nov 18 '15 at 02:12
Well that answer seems like it might have some promise. I just suggested using `mongo` because you said your connection string was analogous to it. — evanmcdonnal, Nov 18 '15 at 02:19

Dmitri Goldring · Accepted Answer · 2015-11-18T02:14:42.913

3

It looks like Cayley is using lib/pq under the covers. lib/pq connection strings look something like this: "user=pqgotest dbname=pqgotest sslmode=verify-full" or "postgres://pqgotest:password@localhost/pqgotest?sslmode=verify-full" For full details see the lib/pq documentation at godoc.org.

(You can see where the sql.Open call is made in cayley/graph/sql/quadstore.go connectSQLTables.)

edited Nov 18 '15 at 02:14

answered Nov 18 '15 at 02:09

Dmitri Goldring

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I got it after checking the godocs, thanks! After that, I ran into an error that said that `db: failed to load data: pq: relation "quads" does not exist`, which I got around by creating a table `quads` according to the query found at https://github.com/google/cayley/blob/master/graph/sql/quadstore.go. After that, I managed to load the data. – Marcus Vinícius Monteiro Nov 18 '15 at 02:39

How to use Cayley with a Postgres backend?

1 Answers1