database/sql doesn't return error for query-string-destination if NULL bug or feature

[Stephan Lukits]

I passed a string-type pointer (as last destination) to a sql.DB.Query call which had a NULL value as field value. No error was returned and all other fields got the appropriate values but the connection was silently closed.  I noticed because it was an in-memory (sqlite3) database which all of a sudden appeard empty.

I could fix the problem for me by passing a sql.NullString instead of a string destination.  Maybe its interesting to know.

Kind regards Stephan 

[Marcin Romaszewicz]

Which sqlite driver are you using? That sounds like a bug.

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[Stephan Lukits]

On Friday, 11 September 2020 at 21:04:11 UTC+3 mar...@gmail.com wrote:

Which sqlite driver are you using? That sounds like a bug.

"github.com/mattn/go-sqlite3"

 

On Fri, Sep 11, 2020 at 10:56 AM Stephan Lukits wrote:

I passed a string-type pointer (as last destination) to a sql.DB.Query call which had a NULL value as field value. No error was returned

Here I was wrong.  The error is returned by the Scan(...)-call (which I didn't catch, these are my first steps with go ...)

The reason why I was fixated on the Query-call was the way I tracked the cause:

I printed the functioning and not functioning DB-connection and saw that they differ

&{0 {:memory: 0xc00000e0e0} 0 {0 0} [0xc000126a20] ...

&{0 {:memory: 0xc00000e0e0} 0 {0 0} [] ...

at the slice. Pinging the non-functioning DB-connection put a new addres into the empty slice, so I assumed that this slice holds the open connections.

Then I narroed the two lines until I found the line where the switch to the empty slice happand which was oddly the Query-call.

The Questions which remain are, dose this connection gets closed allways when an error appears? Is it a bug? 

Can I use the API to figure if this connection was closed? Ping doesn't work because it just creates a new connection and pretends everything is fine.

My settings are:

.SetMaxOpenConns(1)

.SetConnMaxLifetime(0)

.SetConnMaxIdleTime(0)

(because I really don't want this connection to close ;)

 

Thanks Stephan

[Tamás Gulácsi]

database/sql.DB is a pool. If you don't want to close it, SetMaxIdleConns(1), or better, use a db.Conn().

[Stephan Lukits]

On 9/12/20 8:25 AM, Tamás Gulácsi wrote:
> database/sql.DB is a pool. If you don't want to close it,
> SetMaxIdleConns(1), or better, use a db.Conn().
>

Thanks for the hint.