On Mon, Jul 22, 2019 at 10:37 AM Robert Engels <reng...@ix.netcom.com> wrote:
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> -----Original Message-----
> >From: Burak Serdar <bser...@ieee.org>
> >Sent: Jul 22, 2019 11:13 AM
> >To: Tong Sun <suntong...@gmail.com>
> >Cc: golang-nuts <golang-nuts@googlegroups.com>
> >Subject: Re: [go-nuts] Variable life time -- sql.DB connection defer closing
> >question
> >
> >On Mon, Jul 22, 2019 at 9:35 AM Tong Sun <suntong...@gmail.com> wrote:
> >>
> >> All SQL DB statements need a sql.DB connection:
> >>
> >> var conn *sql.DB = ...
> >> defer conn.Close()
> >>
> >> statement, err := conn.Prepare(SQL)
> >>
> >>
> >> My question is, if I want to reuse the `conn` variable later on in the
> >> same function,
> >>
> >> conn, err = sql.Open("mssql", NewConnString)
> >
> >If you didn't close conn here, then it will leak. The defer will close
> >the second connection, not the first.
> >You can add a second defer after opening the second connection. Or,
> >use a different variable and defer closing of that as well.
> >
> >Closing the first connection manually before opening the second won't
> >work. The first defer will try to close the first connection. Defer
> >evaluates its arguments when it is declared, not when it runs.
> >
> >
> >>
> >>
> >> Do I need to put another `defer conn.Close()` after it, or the first
> >> `defer conn.Close()` still applies? Or I should call `conn.Close()`
> >> explicitly beforehand?
> >>
> >> thanks
> >>
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> I don't think that is true. The first defer will be scheduled with the first
> conn arg (since it is evaluated at call time). You need another defer after
> the second open. You will end up with Close being called twice from defer
> which is what you want.
I thought that's what I said as well. What part is wrong?
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