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func (db *DB) PrepareContext(ctx context.Context, query string) (*Stmt, error) {
var stmt *Stmt
var err error
for i := 0; i < maxBadConnRetries; i++ {
stmt, err = db.prepare(ctx, query, cachedOrNewConn)
if err != driver.ErrBadConn {
break
}
}
if err == driver.ErrBadConn {
return db.prepare(ctx, query, alwaysNewConn)
// Prepare creates a prepared statement for later queries or executions.
// Multiple queries or executions may be run concurrently from the
// returned statement.
// The caller must call the statement's Close method
// when the statement is no longer needed.
func (db *DB) Prepare(query string) (*Stmt, error) {
return db.PrepareContext(context.Background(), query)
}
func (db *DB) prepare(ctx context.Context, query string, strategy connReuseStrategy) (*Stmt, error) {
// TODO: check if db.driver supports an optional
// driver.Preparer interface and call that instead, if so,
// otherwise we make a prepared statement that's bound
// to a connection, and to execute this prepared statement
// we either need to use this connection (if it's free), else
// get a new connection + re-prepare + execute on that one.
dc, err := db.conn(ctx, strategy)
if err != nil {
return nil, err
}
var si driver.Stmt
withLock(dc, func() {
si, err = dc.prepareLocked(ctx, query)
db.putConn(dc, err)
db: db,
query: query,
css: []connStmt{{dc, si}},
lastNumClosed: atomic.LoadUint64(&db.numClosed),
db.putConn(dc, nil)
return stmt, nil
}
// ExecContext executes a query without returning any rows.
// The args are for any placeholder parameters in the query.
func (db *DB) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
var err error
for i := 0; i < maxBadConnRetries; i++ {
res, err = db.exec(ctx, query, args, cachedOrNewConn)
if err != driver.ErrBadConn {
break
}
if err == driver.ErrBadConn {
return db.exec(ctx, query, args, alwaysNewConn)
// Exec executes a query without returning any rows.
// The args are for any placeholder parameters in the query.
func (db *DB) Exec(query string, args ...interface{}) (Result, error) {
return db.ExecContext(context.Background(), query, args...)
}
func (db *DB) exec(ctx context.Context, query string, args []interface{}, strategy connReuseStrategy) (res Result, err error) {
dc, err := db.conn(ctx, strategy)
if err != nil {
return nil, err
}
db.putConn(dc, err)
if execer, ok := dc.ci.(driver.Execer); ok {
var dargs []driver.NamedValue
dargs, err = driverArgs(nil, args)
if err != nil {
return nil, err
}
var resi driver.Result
withLock(dc, func() {
resi, err = ctxDriverExec(ctx, execer, query, dargs)
if err != driver.ErrSkip {
if err != nil {
return nil, err
}
return driverResult{dc, resi}, nil
var si driver.Stmt
withLock(dc, func() {
si, err = ctxDriverPrepare(ctx, dc.ci, query)
if err != nil {
return nil, err
}
defer withLock(dc, func() { si.Close() })
return resultFromStatement(ctx, driverStmt{dc, si}, args...)
// QueryContext executes a query that returns rows, typically a SELECT.
// The args are for any placeholder parameters in the query.
func (db *DB) QueryContext(ctx context.Context, query string, args ...interface{}) (*Rows, error) {
var rows *Rows
var err error
for i := 0; i < maxBadConnRetries; i++ {
rows, err = db.query(ctx, query, args, cachedOrNewConn)
if err != driver.ErrBadConn {
break
}
}
if err == driver.ErrBadConn {
return db.query(ctx, query, args, alwaysNewConn)
return rows, err
}
// Query executes a query that returns rows, typically a SELECT.
// The args are for any placeholder parameters in the query.
func (db *DB) Query(query string, args ...interface{}) (*Rows, error) {
return db.QueryContext(context.Background(), query, args...)
}
func (db *DB) query(ctx context.Context, query string, args []interface{}, strategy connReuseStrategy) (*Rows, error) {
ci, err := db.conn(ctx, strategy)
if err != nil {
return nil, err
}
return db.queryConn(ctx, ci, ci.releaseConn, query, args)
}
// queryConn executes a query on the given connection.
// The connection gets released by the releaseConn function.
func (db *DB) queryConn(ctx context.Context, dc *driverConn, releaseConn func(error), query string, args []interface{}) (*Rows, error) {
if queryer, ok := dc.ci.(driver.Queryer); ok {
dargs, err := driverArgs(nil, args)
if err != nil {
releaseConn(err)
return nil, err
}
var rowsi driver.Rows
withLock(dc, func() {
rowsi, err = ctxDriverQuery(ctx, queryer, query, dargs)
if err != driver.ErrSkip {
if err != nil {
releaseConn(err)
return nil, err
}
// Note: ownership of dc passes to the *Rows, to be freed
// with releaseConn.
rows := &Rows{
releaseConn: releaseConn,
rowsi: rowsi,
}
rows.initContextClose(ctx)
return rows, nil
}
}
var si driver.Stmt
var err error
withLock(dc, func() {
si, err = ctxDriverPrepare(ctx, dc.ci, query)
releaseConn(err)
ds := driverStmt{dc, si}
rowsi, err := rowsiFromStatement(ctx, ds, args...)
if err != nil {
withLock(dc, func() {
si.Close()
})
return nil, err
}
// Note: ownership of ci passes to the *Rows, to be freed
// with releaseConn.
rows := &Rows{
releaseConn: releaseConn,
rowsi: rowsi,
closeStmt: si,
rows.initContextClose(ctx)
// QueryRowContext executes a query that is expected to return at most one row.
// QueryRowContext always returns a non-nil value. Errors are deferred until
// Row's Scan method is called.
func (db *DB) QueryRowContext(ctx context.Context, query string, args ...interface{}) *Row {
rows, err := db.QueryContext(ctx, query, args...)
return &Row{rows: rows, err: err}
}
// QueryRow executes a query that is expected to return at most one row.
// QueryRow always returns a non-nil value. Errors are deferred until
// Row's Scan method is called.
func (db *DB) QueryRow(query string, args ...interface{}) *Row {
return db.QueryRowContext(context.Background(), query, args...)
// BeginContext starts a transaction. If a non-default isolation level is used
// that the driver doesn't support an error will be returned. Different drivers
// may have slightly different meanings for the same isolation level.
func (db *DB) BeginContext(ctx context.Context) (*Tx, error) {
for i := 0; i < maxBadConnRetries; i++ {
tx, err = db.begin(ctx, cachedOrNewConn)
if err != driver.ErrBadConn {
break
}
}
if err == driver.ErrBadConn {
return db.begin(ctx, alwaysNewConn)
// Begin starts a transaction. The default isolation level is dependent on
// the driver.
func (db *DB) Begin() (*Tx, error) {
return db.BeginContext(context.Background())
}
func (db *DB) begin(ctx context.Context, strategy connReuseStrategy) (tx *Tx, err error) {
dc, err := db.conn(ctx, strategy)
if err != nil {
return nil, err
}
var txi driver.Tx
withLock(dc, func() {
txi, err = ctxDriverBegin(ctx, dc.ci)
db.putConn(dc, err)
return nil, err
// Schedule the transaction to rollback when the context is cancelled.
// The cancel function in Tx will be called after done is set to true.
ctx, cancel := context.WithCancel(ctx)
tx = &Tx{
db: db,
dc: dc,
txi: txi,
cancel: cancel,
}
go func() {
select {
case <-ctx.Done():
if !tx.done {
tx.Rollback()
}
}
}()
return tx, nil
// Driver returns the database's underlying driver.
func (db *DB) Driver() driver.Driver {
return db.driver
}
// Tx is an in-progress database transaction.
//
// A transaction must end with a call to Commit or Rollback.
//
// After a call to Commit or Rollback, all operations on the
// transaction fail with ErrTxDone.
//
// The statements prepared for a transaction by calling
// the transaction's Prepare or Stmt methods are closed
// by the call to Commit or Rollback.
// dc is owned exclusively until Commit or Rollback, at which point
// it's returned with putConn.
dc *driverConn
txi driver.Tx
// done transitions from false to true exactly once, on Commit
// or Rollback. once done, all operations fail with
// ErrTxDone.
// All Stmts prepared for this transaction. These will be closed after the
// transaction has been committed or rolled back.
stmts struct {
sync.Mutex
v []*Stmt
}
// cancel is called after done transitions from false to true.
cancel func()
// ErrTxDone is returned by any operation that is performed on a transaction
// that has already been committed or rolled back.
var ErrTxDone = errors.New("sql: Transaction has already been committed or rolled back")
func (tx *Tx) close(err error) {
if tx.done {
panic("double close") // internal error
}
tx.done = true
tx.db.putConn(tx.dc, err)
tx.dc = nil
tx.txi = nil
}
func (tx *Tx) grabConn(ctx context.Context) (*driverConn, error) {
return nil, ErrTxDone
return tx.dc, nil
// Closes all Stmts prepared for this transaction.
func (tx *Tx) closePrepared() {
tx.stmts.Lock()
defer tx.stmts.Unlock()
for _, stmt := range tx.stmts.v {
stmt.Close()
}
}
// Commit commits the transaction.
return ErrTxDone
var err error
withLock(tx.dc, func() {
err = tx.txi.Commit()
})
if err != driver.ErrBadConn {
tx.closePrepared()
}
return err
}
// Rollback aborts the transaction.
func (tx *Tx) Rollback() error {
return ErrTxDone
var err error
withLock(tx.dc, func() {
err = tx.txi.Rollback()
})
if err != driver.ErrBadConn {
tx.closePrepared()
}
return err
// Prepare creates a prepared statement for use within a transaction.
// The returned statement operates within the transaction and can no longer
// be used once the transaction has been committed or rolled back.
//
// To use an existing prepared statement on this transaction, see Tx.Stmt.
//
// The provided context will be used for the preparation of the context, not
// for the execution of the returned statement. The returned statement
// will run in the transaction context.
func (tx *Tx) PrepareContext(ctx context.Context, query string) (*Stmt, error) {
// TODO(bradfitz): We could be more efficient here and either
// provide a method to take an existing Stmt (created on
// perhaps a different Conn), and re-create it on this Conn if
// necessary. Or, better: keep a map in DB of query string to
// Stmts, and have Stmt.Execute do the right thing and
// re-prepare if the Conn in use doesn't have that prepared
// statement. But we'll want to avoid caching the statement
// in the case where we only call conn.Prepare implicitly
// (such as in db.Exec or tx.Exec), but the caller package
// can't be holding a reference to the returned statement.
// Perhaps just looking at the reference count (by noting
// Stmt.Close) would be enough. We might also want a finalizer
// on Stmt to drop the reference count.
if err != nil {
return nil, err
}
var si driver.Stmt
withLock(dc, func() {
si, err = dc.ci.Prepare(query)
})
if err != nil {
return nil, err
}
stmt := &Stmt{
db: tx.db,
tx: tx,
txsi: &driverStmt{
Locker: dc,
si: si,
},
query: query,
}
tx.stmts.Lock()
tx.stmts.v = append(tx.stmts.v, stmt)
tx.stmts.Unlock()
return stmt, nil
// Prepare creates a prepared statement for use within a transaction.
//
// The returned statement operates within the transaction and can no longer
// be used once the transaction has been committed or rolled back.
//
// To use an existing prepared statement on this transaction, see Tx.Stmt.
func (tx *Tx) Prepare(query string) (*Stmt, error) {
return tx.PrepareContext(context.Background(), query)
}
// StmtContext returns a transaction-specific prepared statement from
// an existing statement.
//
// Example:
// updateMoney, err := db.Prepare("UPDATE balance SET money=money+? WHERE id=?")
// ...
// tx, err := db.Begin()
// ...
// res, err := tx.StmtContext(ctx, updateMoney).Exec(123.45, 98293203)
//
// The returned statement operates within the transaction and can no longer
// be used once the transaction has been committed or rolled back.
func (tx *Tx) StmtContext(ctx context.Context, stmt *Stmt) *Stmt {
// TODO(bradfitz): optimize this. Currently this re-prepares
// each time. This is fine for now to illustrate the API but
// we should really cache already-prepared statements
// per-Conn. See also the big comment in Tx.Prepare.
if tx.db != stmt.db {
return &Stmt{stickyErr: errors.New("sql: Tx.Stmt: statement from different database used")}
}
if err != nil {
return &Stmt{stickyErr: err}
}
var si driver.Stmt
withLock(dc, func() {
si, err = dc.ci.Prepare(stmt.query)
})
txs := &Stmt{
db: tx.db,
tx: tx,
txsi: &driverStmt{
Locker: dc,
si: si,
},
query: stmt.query,
stickyErr: err,
}
tx.stmts.Lock()
tx.stmts.v = append(tx.stmts.v, txs)
tx.stmts.Unlock()
return txs
}
// Stmt returns a transaction-specific prepared statement from
// an existing statement.
//
// Example:
// updateMoney, err := db.Prepare("UPDATE balance SET money=money+? WHERE id=?")
// ...
// tx, err := db.Begin()
// ...
// res, err := tx.Stmt(updateMoney).Exec(123.45, 98293203)
//
// The returned statement operates within the transaction and can no longer
// be used once the transaction has been committed or rolled back.
func (tx *Tx) Stmt(stmt *Stmt) *Stmt {
return tx.StmtContext(context.Background(), stmt)
}
// ExecContext executes a query that doesn't return rows.
// For example: an INSERT and UPDATE.
func (tx *Tx) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
dc, err := tx.grabConn(ctx)
if err != nil {
return nil, err
}
if execer, ok := dc.ci.(driver.Execer); ok {
dargs, err := driverArgs(nil, args)
if err != nil {
return nil, err
}
var resi driver.Result
withLock(dc, func() {
resi, err = ctxDriverExec(ctx, execer, query, dargs)
return driverResult{dc, resi}, nil
}
if err != driver.ErrSkip {
return nil, err
}
}
var si driver.Stmt
withLock(dc, func() {
si, err = ctxDriverPrepare(ctx, dc.ci, query)
if err != nil {
return nil, err
}
defer withLock(dc, func() { si.Close() })
return resultFromStatement(ctx, driverStmt{dc, si}, args...)
// Exec executes a query that doesn't return rows.
// For example: an INSERT and UPDATE.
func (tx *Tx) Exec(query string, args ...interface{}) (Result, error) {
return tx.ExecContext(context.Background(), query, args...)
}
// QueryContext executes a query that returns rows, typically a SELECT.
func (tx *Tx) QueryContext(ctx context.Context, query string, args ...interface{}) (*Rows, error) {
dc, err := tx.grabConn(ctx)
if err != nil {
return nil, err
releaseConn := func(error) {}
return tx.db.queryConn(ctx, dc, releaseConn, query, args)
}
// Query executes a query that returns rows, typically a SELECT.
func (tx *Tx) Query(query string, args ...interface{}) (*Rows, error) {
return tx.QueryContext(context.Background(), query, args...)
}
// QueryRowContext executes a query that is expected to return at most one row.
// QueryRowContext always returns a non-nil value. Errors are deferred until
// Row's Scan method is called.
func (tx *Tx) QueryRowContext(ctx context.Context, query string, args ...interface{}) *Row {
rows, err := tx.QueryContext(ctx, query, args...)
return &Row{rows: rows, err: err}
}
// QueryRow executes a query that is expected to return at most one row.
// QueryRow always returns a non-nil value. Errors are deferred until
// Row's Scan method is called.
func (tx *Tx) QueryRow(query string, args ...interface{}) *Row {
return tx.QueryRowContext(context.Background(), query, args...)
}
// connStmt is a prepared statement on a particular connection.
type connStmt struct {
dc *driverConn
// Stmt is a prepared statement.
// A Stmt is safe for concurrent use by multiple goroutines.
type Stmt struct {
// Immutable:
db *DB // where we came from
query string // that created the Stmt
stickyErr error // if non-nil, this error is returned for all operations
closemu sync.RWMutex // held exclusively during close, for read otherwise.
// If in a transaction, else both nil:
tx *Tx
txsi *driverStmt
mu sync.Mutex // protects the rest of the fields
// css is a list of underlying driver statement interfaces
// that are valid on particular connections. This is only
// used if tx == nil and one is found that has idle
// connections. If tx != nil, txsi is always used.
// lastNumClosed is copied from db.numClosed when Stmt is created
// without tx and closed connections in css are removed.
lastNumClosed uint64
// ExecContext executes a prepared statement with the given arguments and
// returns a Result summarizing the effect of the statement.
func (s *Stmt) ExecContext(ctx context.Context, args ...interface{}) (Result, error) {
s.closemu.RLock()
defer s.closemu.RUnlock()
var res Result
for i := 0; i < maxBadConnRetries; i++ {
dc, releaseConn, si, err := s.connStmt(ctx)
if err != nil {
if err == driver.ErrBadConn {
continue
}
return nil, err
}
res, err = resultFromStatement(ctx, driverStmt{dc, si}, args...)
releaseConn(err)
if err != driver.ErrBadConn {
return res, err
}
}
return nil, driver.ErrBadConn
// Exec executes a prepared statement with the given arguments and
// returns a Result summarizing the effect of the statement.
func (s *Stmt) Exec(args ...interface{}) (Result, error) {
return s.ExecContext(context.Background(), args...)
}
func driverNumInput(ds driverStmt) int {
ds.Lock()
defer ds.Unlock() // in case NumInput panics
return ds.si.NumInput()
}
func resultFromStatement(ctx context.Context, ds driverStmt, args ...interface{}) (Result, error) {
want := driverNumInput(ds)
// -1 means the driver doesn't know how to count the number of
// placeholders, so we won't sanity check input here and instead let the
// driver deal with errors.
if want != -1 && len(args) != want {
return nil, fmt.Errorf("sql: expected %d arguments, got %d", want, len(args))
dargs, err := driverArgs(&ds, args)
if err != nil {
return nil, err
ds.Lock()
defer ds.Unlock()
resi, err := ctxDriverStmtExec(ctx, ds.si, dargs)
if err != nil {
return nil, err
}
return driverResult{ds.Locker, resi}, nil
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// removeClosedStmtLocked removes closed conns in s.css.
//
// To avoid lock contention on DB.mu, we do it only when
// s.db.numClosed - s.lastNum is large enough.
func (s *Stmt) removeClosedStmtLocked() {
t := len(s.css)/2 + 1
if t > 10 {
t = 10
}
dbClosed := atomic.LoadUint64(&s.db.numClosed)
if dbClosed-s.lastNumClosed < uint64(t) {
return
}
s.db.mu.Lock()
for i := 0; i < len(s.css); i++ {
if s.css[i].dc.dbmuClosed {
s.css[i] = s.css[len(s.css)-1]
s.css = s.css[:len(s.css)-1]
i--
}
}
s.db.mu.Unlock()
s.lastNumClosed = dbClosed
}
// connStmt returns a free driver connection on which to execute the
// statement, a function to call to release the connection, and a
// statement bound to that connection.
func (s *Stmt) connStmt(ctx context.Context) (ci *driverConn, releaseConn func(error), si driver.Stmt, err error) {
if err = s.stickyErr; err != nil {
return
}
s.mu.Lock()
if s.closed {
// In a transaction, we always use the connection that the
// transaction was created on.
if s.tx != nil {
s.mu.Unlock()
ci, err = s.tx.grabConn(ctx) // blocks, waiting for the connection.
if err != nil {
return
}
releaseConn = func(error) {}
return ci, releaseConn, s.txsi.si, nil
s.removeClosedStmtLocked()
dc, err := s.db.conn(ctx, cachedOrNewConn)
if err != nil {
return nil, nil, nil, err
}
s.mu.Lock()
for _, v := range s.css {
if v.dc == dc {
s.mu.Unlock()
return dc, dc.releaseConn, v.si, nil
s.mu.Unlock()
// No luck; we need to prepare the statement on this connection
withLock(dc, func() {
si, err = dc.prepareLocked(ctx, s.query)
if err != nil {
s.db.putConn(dc, err)
return nil, nil, nil, err
}
s.mu.Lock()
cs := connStmt{dc, si}
s.css = append(s.css, cs)
s.mu.Unlock()
return dc, dc.releaseConn, si, nil
// QueryContext executes a prepared query statement with the given arguments
// and returns the query results as a *Rows.
func (s *Stmt) QueryContext(ctx context.Context, args ...interface{}) (*Rows, error) {
s.closemu.RLock()
defer s.closemu.RUnlock()
var rowsi driver.Rows
for i := 0; i < maxBadConnRetries; i++ {
dc, releaseConn, si, err := s.connStmt(ctx)
if err != nil {
if err == driver.ErrBadConn {
continue
}
return nil, err
}
rowsi, err = rowsiFromStatement(ctx, driverStmt{dc, si}, args...)
if err == nil {
// Note: ownership of ci passes to the *Rows, to be freed
// with releaseConn.
rows := &Rows{
dc: dc,
rowsi: rowsi,
// releaseConn set below
}
rows.initContextClose(ctx)
s.db.addDep(s, rows)
rows.releaseConn = func(err error) {
releaseConn(err)
s.db.removeDep(s, rows)
}
return rows, nil
}
if err != driver.ErrBadConn {
return nil, err
}
return nil, driver.ErrBadConn
// Query executes a prepared query statement with the given arguments
// and returns the query results as a *Rows.
func (s *Stmt) Query(args ...interface{}) (*Rows, error) {
return s.QueryContext(context.Background(), args...)
}
func rowsiFromStatement(ctx context.Context, ds driverStmt, args ...interface{}) (driver.Rows, error) {
var want int
withLock(ds, func() {
want = ds.si.NumInput()
})
// -1 means the driver doesn't know how to count the number of
// placeholders, so we won't sanity check input here and instead let the
// driver deal with errors.
if want != -1 && len(args) != want {
return nil, fmt.Errorf("sql: statement expects %d inputs; got %d", want, len(args))
dargs, err := driverArgs(&ds, args)
if err != nil {
return nil, err
}
ds.Lock()
defer ds.Unlock()
rowsi, err := ctxDriverStmtQuery(ctx, ds.si, dargs)
if err != nil {
return nil, err
}
return rowsi, nil
// QueryRowContext executes a prepared query statement with the given arguments.
// If an error occurs during the execution of the statement, that error will
// be returned by a call to Scan on the returned *Row, which is always non-nil.
// If the query selects no rows, the *Row's Scan will return ErrNoRows.
// Otherwise, the *Row's Scan scans the first selected row and discards
// the rest.
//
// Example usage:
//
// var name string
// err := nameByUseridStmt.QueryRowContext(ctx, id).Scan(&name)
func (s *Stmt) QueryRowContext(ctx context.Context, args ...interface{}) *Row {
rows, err := s.QueryContext(ctx, args...)
if err != nil {
return &Row{err: err}
}
return &Row{rows: rows}
}
// QueryRow executes a prepared query statement with the given arguments.
// If an error occurs during the execution of the statement, that error will
// be returned by a call to Scan on the returned *Row, which is always non-nil.
// If the query selects no rows, the *Row's Scan will return ErrNoRows.
// Otherwise, the *Row's Scan scans the first selected row and discards
// the rest.
//
// Example usage:
//
// var name string
// err := nameByUseridStmt.QueryRow(id).Scan(&name)
func (s *Stmt) QueryRow(args ...interface{}) *Row {
return s.QueryRowContext(context.Background(), args...)
}
// Close closes the statement.
s.closemu.Lock()
defer s.closemu.Unlock()
if s.stickyErr != nil {
return s.stickyErr
}
s.mu.Lock()
if s.closed {
return nil
}
s.closed = true
if s.tx != nil {
defer s.mu.Unlock()
return s.txsi.Close()
return s.db.removeDep(s, s)
}
func (s *Stmt) finalClose() error {
s.mu.Lock()
defer s.mu.Unlock()
if s.css != nil {
for _, v := range s.css {
s.db.noteUnusedDriverStatement(v.dc, v.si)
v.dc.removeOpenStmt(v.si)
}
s.css = nil
}
return nil
}
// Rows is the result of a query. Its cursor starts before the first row
// of the result set. Use Next to advance through the rows:
//
// rows, err := db.Query("SELECT ...")
// ...
// defer rows.Close()
// for rows.Next() {
// var id int
// var name string
// err = rows.Scan(&id, &name)
// ...
// }
// err = rows.Err() // get any error encountered during iteration
// ...
type Rows struct {
dc *driverConn // owned; must call releaseConn when closed to release
releaseConn func(error)
rowsi driver.Rows
// closed value is 1 when the Rows is closed.
// Use atomic operations on value when checking value.
closed int32
ctxClose chan struct{} // closed when Rows is closed, may be null.
lasterr error // non-nil only if closed is true
closeStmt driver.Stmt // if non-nil, statement to Close on close
func (rs *Rows) initContextClose(ctx context.Context) {
if ctx.Done() == context.Background().Done() {
return
}
rs.ctxClose = make(chan struct{})
go func() {
select {
case <-ctx.Done():
rs.Close()
case <-rs.ctxClose:
}
}()
}
// Next prepares the next result row for reading with the Scan method. It
// returns true on success, or false if there is no next result row or an error
// happened while preparing it. Err should be consulted to distinguish between
// the two cases.
//
// Every call to Scan, even the first one, must be preceded by a call to Next.
func (rs *Rows) Next() bool {
if rs.isClosed() {
return false
}
if rs.lastcols == nil {
rs.lastcols = make([]driver.Value, len(rs.rowsi.Columns()))
}
rs.lasterr = rs.rowsi.Next(rs.lastcols)
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if rs.lasterr != nil {
// Close the connection if there is a driver error.
if rs.lasterr != io.EOF {
rs.Close()
return false
}
nextResultSet, ok := rs.rowsi.(driver.RowsNextResultSet)
if !ok {
rs.Close()
return false
}
// The driver is at the end of the current result set.
// Test to see if there is another result set after the current one.
// Only close Rows if there is no futher result sets to read.
if !nextResultSet.HasNextResultSet() {
rs.Close()
}
return false
}
return true
}
// NextResultSet prepares the next result set for reading. It returns true if
// there is further result sets, or false if there is no further result set
// or if there is an error advancing to it. The Err method should be consulted
// to distinguish between the two cases.
//
// After calling NextResultSet, the Next method should always be called before
// scanning. If there are further result sets they may not have rows in the result
// set.
func (rs *Rows) NextResultSet() bool {
if rs.isClosed() {
return false
}
rs.lastcols = nil