unix domain socket in URL host position fails with "invalid URL escape"

[dhduvall]

If I try to ping a database with the URL

postgresql://%2Fvar%2Flib%2Fpostgresql/dbname

as described in the Postgres manual section "Connection Strings", I get the following error message:

parse postgresql://%2Fvar%2Flib%2Fpostgresql/dbname: invalid URL escape "%2F"

This is the same error you get if use use the Parse() method from net/url on that string.

Here's the complete program:

package main

import (
        "database/sql"
        "fmt"

        _ "github.com/lib/pq"
)

func main() {
        connStr := `postgresql://%2Fvar%2Flib%2Fpostgresql/dbname`
        db, _ := sql.Open("postgres", connStr)
        err := db.Ping()
        fmt.Println(err)
}

It all works fine if I put the "host" in the query string (?host=/var/lib/postgresql).

[Moulick]

Can we please give this issue some love 😄

[mmierzwa]

Srsly, 6 years?! This will soon beat the "Duke Nukem Forever" xD

[ayang64]

I don't think this is a bug in lib/pq. I think it is exhibiting the correct behavior as only non-ASCII characters should be escaped this way. The link below does a better job of explaining it than I can at the moment:

golang/go#30844 (comment)

I think the answer is: don't do that.

But, paradoxically, the Go URL encoder will escape the first slash if you pack a URL this way:

package main

import (
	"log"
	"net/url"
)

func main() {
	u := url.URL{
		Host: "/tmp/.s.Foo.Bar",
	}
	log.Printf("%s", &u)
}

So I think there's a lack of symmetry here -- the encoder will escape it but the decoder will not unescape it.

There's a bug here somewhere but I don't think it is in lib/pq. I'm not even sure if it is in Go. Maybe it is in our expectations.

I think the problem is that URLs were never intended to use a filepath as a "host" -- this is why passing the host (unix scoket path) as a query parameter works well.

This problem does seem to be unique to connection URLs that are parsed with Go's net/url paackage.

Maybe the best solution is to use the original postgresql key/value pair connection strings.

[ayang64]

Can we close this issue as "wont fix" or "not a bug" or something?

[arp242]

There's a bug here somewhere but I don't think it is in lib/pq. I'm not even sure if it is in Go. Maybe it is in our expectations.

I think the expectation of connection strings that work with psql also work here is a reasonable one, even though they're not strictly valid.

Looking at the psql function for this, it processes %-escapes before anything else, so I think we can just copy that?

https://github.com/postgres/postgres/blob/451c439/src/interfaces/libpq/fe-connect.c#L7273