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database/sql: defer db.putConn(ci, err) pattern, err is always nil #3950

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gopherbot opened this issue Aug 14, 2012 · 2 comments
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database/sql: defer db.putConn(ci, err) pattern, err is always nil #3950

gopherbot opened this issue Aug 14, 2012 · 2 comments

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@gopherbot
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@gopherbot gopherbot commented Aug 14, 2012

by pcrosby:

In database/sql/sql.go, all the calls to db.putConn that use a defer will always pass
nil for the error.

For example, assuming the following exec function gets to the "defer db.putConn(ci,
err)" line, err will always be nil, no matter what happens to err after the
"defer..." line (since the arguments to the deferred function are evaluated
when the defer executes, not when the call executes).

I know putConn only cares if err is a driver.ErrBadConn, but it seems to me like that is
a possible error in many of the functions in sql.go that use this defer db.putConn(ci,
err) pattern.

func (db *DB) exec(query string, sargs []driver.Value) (res Result, err error) {
    ci, err := db.conn()
    if err != nil {
        return nil, err
    }
    defer db.putConn(ci, err)

    if execer, ok := ci.(driver.Execer); ok {
        resi, err := execer.Exec(query, sargs)
        if err != driver.ErrSkip {
            if err != nil {
                return nil, err
            }
            return result{resi}, nil
        }
    }

    sti, err := ci.Prepare(query)
    if err != nil {
        return nil, err
    }
    defer sti.Close()

    resi, err := sti.Exec(sargs)
    if err != nil {
        return nil, err
    }
    return result{resi}, nil
}
@gopherbot
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@gopherbot gopherbot commented Aug 14, 2012

Comment 1 by pcrosby:

Sorry, this is a duplicate of 3777.  Please disregard.
@ianlancetaylor
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@ianlancetaylor ianlancetaylor commented Aug 14, 2012

Comment 2:

Status changed to Duplicate.

Merged into issue #3777.

@mikioh mikioh changed the title database/sql defer db.putConn(ci, err) pattern, err is always nil database/sql: defer db.putConn(ci, err) pattern, err is always nil Feb 18, 2015
@golang golang locked and limited conversation to collaborators Jun 24, 2016
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