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Fixed sqlserver not actually getting a lock if lock is already set #1186

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merged 1 commit into from
Apr 25, 2025
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Fixed sqlserver not actually getting a lock if lock is already set #1186

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20 changes: 13 additions & 7 deletions database/sqlserver/sqlserver.go
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ var (
ErrMultipleAuthOptionsPassed = fmt.Errorf("both password and useMsi=true were passed.")
)

var lockErrorMap = map[mssql.ReturnStatus]string{
var lockErrorMap = map[int]string{
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Can you continue to use mssql.ReturnStatus?

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Hi!

Sorry for the late reply!

I think int is the correct choice here, since we are selecting an int result (DECLARE @lockResult int;).

Note that in the previous version, this map was never used, since status variable was always 0 (this statement does not actually write anything to status variable: ss.conn.ExecContext(context.Background(), query, aid, &status)).

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Ahh, you're right. The docs mention ReturnStatus being used for PROCs

-1: "The lock request timed out.",
-2: "The lock request was canceled.",
-3: "The lock request was chosen as a deadlock victim.",
Expand Down Expand Up @@ -198,18 +198,24 @@ func (ss *SQLServer) Lock() error {
return err
}

// This will either obtain the lock immediately and return true,
// or return false if the lock cannot be acquired immediately.
// This will block until the lock is acquired.
// MS Docs: sp_getapplock: https://docs.microsoft.com/en-us/sql/relational-databases/system-stored-procedures/sp-getapplock-transact-sql?view=sql-server-2017
query := `EXEC sp_getapplock @Resource = @p1, @LockMode = 'Update', @LockOwner = 'Session', @LockTimeout = 0`
query := `
DECLARE @lockResult int;
EXEC @lockResult = sp_getapplock @Resource = @p1, @LockMode = 'Exclusive', @LockOwner = 'Session', @LockTimeout = -1;
SELECT @lockResult;`

var status mssql.ReturnStatus
if _, err = ss.conn.ExecContext(context.Background(), query, aid, &status); err == nil && status > -1 {
var status int
if err = ss.conn.QueryRowContext(context.Background(), query, aid).Scan(&status); err == nil && status > -1 {
return nil
} else if err != nil {
return &database.Error{OrigErr: err, Err: "try lock failed", Query: []byte(query)}
} else {
return &database.Error{Err: fmt.Sprintf("try lock failed with error %v: %v", status, lockErrorMap[status]), Query: []byte(query)}
errorDescription, ok := lockErrorMap[status]
if !ok {
errorDescription = "Unknown error"
}
return &database.Error{Err: fmt.Sprintf("try lock failed with error %v: %v", status, errorDescription), Query: []byte(query)}
}
})
}
Expand Down