libgo: update to Go 1.8 release candidate 1

Compiler changes: * Change map assignment to use mapassign and assign value directly. * Change string iteration to use decoderune, faster for ASCII strings. * Change makeslice to take int, and use makeslice64 for larger values. * Add new noverflow field to hmap struct used for maps. Unresolved problems, to be fixed later: * Commented out test in go/types/sizes_test.go that doesn't compile. * Commented out reflect.TestStructOf test for padding after zero-sized field. Reviewed-on: https://go-review.googlesource.com/35231 gotools/: Updates for Go 1.8rc1. * Makefile.am (go_cmd_go_files): Add bug.go. (s-zdefaultcc): Write defaultPkgConfig. * Makefile.in: Rebuild. From-SVN: r244456
author: Ian Lance Taylor <iant@golang.org> 2017-01-14 00:05:42 +0000
committer: Ian Lance Taylor <ian@gcc.gnu.org> 2017-01-14 00:05:42 +0000
commit: c2047754c300b68c05d65faa8dc2925fe67b71b4 (patch)
tree: e183ae81a1f48a02945cb6de463a70c5be1b06f6 /libgo/go/database/sql/sql.go
parent: 829afb8f05602bb31c9c597b24df7377fed4f059 (diff)
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1 files changed, 691 insertions, 225 deletions
diff --git a/libgo/go/database/sql/sql.go b/libgo/go/database/sql/sql.go
index 09de1c3..0fa7c34 100644
--- a/libgo/go/database/sql/sql.go
+++ b/libgo/go/database/sql/sql.go
@@ -8,15 +8,20 @@
 // The sql package must be used in conjunction with a database driver.
 // See https://golang.org/s/sqldrivers for a list of drivers.
 //
-// For more usage examples, see the wiki page at
+// Drivers that do not support context cancelation will not return until
+// after the query is completed.
+//
+// For usage examples, see the wiki page at
 // https://golang.org/s/sqlwiki.
 package sql
 
 import (
+	"context"
 	"database/sql/driver"
 	"errors"
 	"fmt"
 	"io"
+	"reflect"
 	"runtime"
 	"sort"
 	"sync"
@@ -66,6 +71,75 @@ func Drivers() []string {
 	return list
 }
 
+// A NamedArg is a named argument. NamedArg values may be used as
+// arguments to Query or Exec and bind to the corresponding named
+// parameter in the SQL statement.
+//
+// For a more concise way to create NamedArg values, see
+// the Named function.
+type NamedArg struct {
+	_Named_Fields_Required struct{}
+
+	// Name is the name of the parameter placeholder.
+	//
+	// If empty, the ordinal position in the argument list will be
+	// used.
+	//
+	// Name must omit any symbol prefix.
+	Name string
+
+	// Value is the value of the parameter.
+	// It may be assigned the same value types as the query
+	// arguments.
+	Value interface{}
+}
+
+// Named provides a more concise way to create NamedArg values.
+//
+// Example usage:
+//
+//     db.ExecContext(ctx, `
+//         delete from Invoice
+//         where
+//             TimeCreated < @end
+//             and TimeCreated >= @start;`,
+//         sql.Named("start", startTime),
+//         sql.Named("end", endTime),
+//     )
+func Named(name string, value interface{}) NamedArg {
+	// This method exists because the go1compat promise
+	// doesn't guarantee that structs don't grow more fields,
+	// so unkeyed struct literals are a vet error. Thus, we don't
+	// want to allow sql.NamedArg{name, value}.
+	return NamedArg{Name: name, Value: value}
+}
+
+// IsolationLevel is the transaction isolation level used in TxOptions.
+type IsolationLevel int
+
+// Various isolation levels that drivers may support in BeginTx.
+// If a driver does not support a given isolation level an error may be returned.
+//
+// See https://en.wikipedia.org/wiki/Isolation_(database_systems)#Isolation_levels.
+const (
+	LevelDefault IsolationLevel = iota
+	LevelReadUncommitted
+	LevelReadCommitted
+	LevelWriteCommitted
+	LevelRepeatableRead
+	LevelSnapshot
+	LevelSerializable
+	LevelLinearizable
+)
+
+// TxOptions holds the transaction options to be used in DB.BeginTx.
+type TxOptions struct {
+	// Isolation is the transaction isolation level.
+	// If zero, the driver or database's default level is used.
+	Isolation IsolationLevel
+	ReadOnly  bool
+}
+
 // RawBytes is a byte slice that holds a reference to memory owned by
 // the database itself. After a Scan into a RawBytes, the slice is only
 // valid until the next call to Next, Scan, or Close.
@@ -272,7 +346,7 @@ type driverConn struct {
 	ci          driver.Conn
 	closed      bool
 	finalClosed bool // ci.Close has been called
-	openStmt    map[driver.Stmt]bool
+	openStmt    map[*driverStmt]bool
 
 	// guarded by db.mu
 	inUse      bool
@@ -284,10 +358,10 @@ func (dc *driverConn) releaseConn(err error) {
 	dc.db.putConn(dc, err)
 }
 
-func (dc *driverConn) removeOpenStmt(si driver.Stmt) {
+func (dc *driverConn) removeOpenStmt(ds *driverStmt) {
 	dc.Lock()
 	defer dc.Unlock()
-	delete(dc.openStmt, si)
+	delete(dc.openStmt, ds)
 }
 
 func (dc *driverConn) expired(timeout time.Duration) bool {
@@ -297,28 +371,23 @@ func (dc *driverConn) expired(timeout time.Duration) bool {
 	return dc.createdAt.Add(timeout).Before(nowFunc())
 }
 
-func (dc *driverConn) prepareLocked(query string) (driver.Stmt, error) {
-	si, err := dc.ci.Prepare(query)
-	if err == nil {
-		// Track each driverConn's open statements, so we can close them
-		// before closing the conn.
-		//
-		// TODO(bradfitz): let drivers opt out of caring about
-		// stmt closes if the conn is about to close anyway? For now
-		// do the safe thing, in case stmts need to be closed.
-		//
-		// TODO(bradfitz): after Go 1.2, closing driver.Stmts
-		// should be moved to driverStmt, using unique
-		// *driverStmts everywhere (including from
-		// *Stmt.connStmt, instead of returning a
-		// driver.Stmt), using driverStmt as a pointer
-		// everywhere, and making it a finalCloser.
-		if dc.openStmt == nil {
-			dc.openStmt = make(map[driver.Stmt]bool)
-		}
-		dc.openStmt[si] = true
+func (dc *driverConn) prepareLocked(ctx context.Context, query string) (*driverStmt, error) {
+	si, err := ctxDriverPrepare(ctx, dc.ci, query)
+	if err != nil {
+		return nil, err
 	}
-	return si, err
+
+	// Track each driverConn's open statements, so we can close them
+	// before closing the conn.
+	//
+	// Wrap all driver.Stmt is *driverStmt to ensure they are only closed once.
+	if dc.openStmt == nil {
+		dc.openStmt = make(map[*driverStmt]bool)
+	}
+	ds := &driverStmt{Locker: dc, si: si}
+	dc.openStmt[ds] = true
+
+	return ds, nil
 }
 
 // the dc.db's Mutex is held.
@@ -350,17 +419,26 @@ func (dc *driverConn) Close() error {
 }
 
 func (dc *driverConn) finalClose() error {
-	dc.Lock()
+	var err error
 
-	for si := range dc.openStmt {
-		si.Close()
+	// Each *driverStmt has a lock to the dc. Copy the list out of the dc
+	// before calling close on each stmt.
+	var openStmt []*driverStmt
+	withLock(dc, func() {
+		openStmt = make([]*driverStmt, 0, len(dc.openStmt))
+		for ds := range dc.openStmt {
+			openStmt = append(openStmt, ds)
+		}
+		dc.openStmt = nil
+	})
+	for _, ds := range openStmt {
+		ds.Close()
 	}
-	dc.openStmt = nil
-
-	err := dc.ci.Close()
-	dc.ci = nil
-	dc.finalClosed = true
-	dc.Unlock()
+	withLock(dc, func() {
+		dc.finalClosed = true
+		err = dc.ci.Close()
+		dc.ci = nil
+	})
 
 	dc.db.mu.Lock()
 	dc.db.numOpen--
@@ -377,12 +455,21 @@ func (dc *driverConn) finalClose() error {
 type driverStmt struct {
 	sync.Locker // the *driverConn
 	si          driver.Stmt
+	closed      bool
+	closeErr    error // return value of previous Close call
 }
 
+// Close ensures dirver.Stmt is only closed once any always returns the same
+// result.
 func (ds *driverStmt) Close() error {
 	ds.Lock()
 	defer ds.Unlock()
-	return ds.si.Close()
+	if ds.closed {
+		return ds.closeErr
+	}
+	ds.closed = true
+	ds.closeErr = ds.si.Close()
+	return ds.closeErr
 }
 
 // depSet is a finalCloser's outstanding dependencies
@@ -494,18 +581,36 @@ func Open(driverName, dataSourceName string) (*DB, error) {
 	return db, nil
 }
 
-// Ping verifies a connection to the database is still alive,
+// PingContext verifies a connection to the database is still alive,
 // establishing a connection if necessary.
-func (db *DB) Ping() error {
-	// TODO(bradfitz): give drivers an optional hook to implement
-	// this in a more efficient or more reliable way, if they
-	// have one.
-	dc, err := db.conn(cachedOrNewConn)
+func (db *DB) PingContext(ctx context.Context) error {
+	var dc *driverConn
+	var err error
+
+	for i := 0; i < maxBadConnRetries; i++ {
+		dc, err = db.conn(ctx, cachedOrNewConn)
+		if err != driver.ErrBadConn {
+			break
+		}
+	}
+	if err == driver.ErrBadConn {
+		dc, err = db.conn(ctx, alwaysNewConn)
+	}
 	if err != nil {
 		return err
 	}
-	db.putConn(dc, nil)
-	return nil
+
+	if pinger, ok := dc.ci.(driver.Pinger); ok {
+		err = pinger.Ping(ctx)
+	}
+	db.putConn(dc, err)
+	return err
+}
+
+// Ping verifies a connection to the database is still alive,
+// establishing a connection if necessary.
+func (db *DB) Ping() error {
+	return db.PingContext(context.Background())
 }
 
 // Close closes the database, releasing any open resources.
@@ -777,12 +882,19 @@ type connRequest struct {
 var errDBClosed = errors.New("sql: database is closed")
 
 // conn returns a newly-opened or cached *driverConn.
-func (db *DB) conn(strategy connReuseStrategy) (*driverConn, error) {
+func (db *DB) conn(ctx context.Context, strategy connReuseStrategy) (*driverConn, error) {
 	db.mu.Lock()
 	if db.closed {
 		db.mu.Unlock()
 		return nil, errDBClosed
 	}
+	// Check if the context is expired.
+	select {
+	default:
+	case <-ctx.Done():
+		db.mu.Unlock()
+		return nil, ctx.Err()
+	}
 	lifetime := db.maxLifetime
 
 	// Prefer a free connection, if possible.
@@ -808,15 +920,21 @@ func (db *DB) conn(strategy connReuseStrategy) (*driverConn, error) {
 		req := make(chan connRequest, 1)
 		db.connRequests = append(db.connRequests, req)
 		db.mu.Unlock()
-		ret, ok := <-req
-		if !ok {
-			return nil, errDBClosed
-		}
-		if ret.err == nil && ret.conn.expired(lifetime) {
-			ret.conn.Close()
-			return nil, driver.ErrBadConn
+
+		// Timeout the connection request with the context.
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case ret, ok := <-req:
+			if !ok {
+				return nil, errDBClosed
+			}
+			if ret.err == nil && ret.conn.expired(lifetime) {
+				ret.conn.Close()
+				return nil, driver.ErrBadConn
+			}
+			return ret.conn, ret.err
 		}
-		return ret.conn, ret.err
 	}
 
 	db.numOpen++ // optimistically
@@ -844,21 +962,22 @@ func (db *DB) conn(strategy connReuseStrategy) (*driverConn, error) {
 // putConnHook is a hook for testing.
 var putConnHook func(*DB, *driverConn)
 
-// noteUnusedDriverStatement notes that si is no longer used and should
+// noteUnusedDriverStatement notes that ds is no longer used and should
 // be closed whenever possible (when c is next not in use), unless c is
 // already closed.
-func (db *DB) noteUnusedDriverStatement(c *driverConn, si driver.Stmt) {
+func (db *DB) noteUnusedDriverStatement(c *driverConn, ds *driverStmt) {
 	db.mu.Lock()
 	defer db.mu.Unlock()
 	if c.inUse {
 		c.onPut = append(c.onPut, func() {
-			si.Close()
+			ds.Close()
 		})
 	} else {
 		c.Lock()
-		defer c.Unlock()
-		if !c.finalClosed {
-			si.Close()
+		fc := c.finalClosed
+		c.Unlock()
+		if !fc {
+			ds.Close()
 		}
 	}
 }
@@ -952,40 +1071,53 @@ func (db *DB) putConnDBLocked(dc *driverConn, err error) bool {
 // connection to be opened.
 const maxBadConnRetries = 2
 
-// Prepare creates a prepared statement for later queries or executions.
+// PrepareContext 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) {
+//
+// The provided context is used for the preparation of the statement, not for the
+// execution of the statement.
+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(query, cachedOrNewConn)
+		stmt, err = db.prepare(ctx, query, cachedOrNewConn)
 		if err != driver.ErrBadConn {
 			break
 		}
 	}
 	if err == driver.ErrBadConn {
-		return db.prepare(query, alwaysNewConn)
+		return db.prepare(ctx, query, alwaysNewConn)
 	}
 	return stmt, err
 }
 
-func (db *DB) prepare(query string, strategy connReuseStrategy) (*Stmt, error) {
+// 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(strategy)
+	dc, err := db.conn(ctx, strategy)
 	if err != nil {
 		return nil, err
 	}
-	dc.Lock()
-	si, err := dc.prepareLocked(query)
-	dc.Unlock()
+	var ds *driverStmt
+	withLock(dc, func() {
+		ds, err = dc.prepareLocked(ctx, query)
+	})
 	if err != nil {
 		db.putConn(dc, err)
 		return nil, err
@@ -993,7 +1125,7 @@ func (db *DB) prepare(query string, strategy connReuseStrategy) (*Stmt, error) {
 	stmt := &Stmt{
 		db:            db,
 		query:         query,
-		css:           []connStmt{{dc, si}},
+		css:           []connStmt{{dc, ds}},
 		lastNumClosed: atomic.LoadUint64(&db.numClosed),
 	}
 	db.addDep(stmt, stmt)
@@ -1001,25 +1133,31 @@ func (db *DB) prepare(query string, strategy connReuseStrategy) (*Stmt, error) {
 	return stmt, nil
 }
 
-// Exec executes a query without returning any rows.
+// ExecContext 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) {
+func (db *DB) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
 	var res Result
 	var err error
 	for i := 0; i < maxBadConnRetries; i++ {
-		res, err = db.exec(query, args, cachedOrNewConn)
+		res, err = db.exec(ctx, query, args, cachedOrNewConn)
 		if err != driver.ErrBadConn {
 			break
 		}
 	}
 	if err == driver.ErrBadConn {
-		return db.exec(query, args, alwaysNewConn)
+		return db.exec(ctx, query, args, alwaysNewConn)
 	}
 	return res, err
 }
 
-func (db *DB) exec(query string, args []interface{}, strategy connReuseStrategy) (res Result, err error) {
-	dc, err := db.conn(strategy)
+// 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
 	}
@@ -1028,13 +1166,15 @@ func (db *DB) exec(query string, args []interface{}, strategy connReuseStrategy)
 	}()
 
 	if execer, ok := dc.ci.(driver.Execer); ok {
-		dargs, err := driverArgs(nil, args)
+		var dargs []driver.NamedValue
+		dargs, err = driverArgs(nil, args)
 		if err != nil {
 			return nil, err
 		}
-		dc.Lock()
-		resi, err := execer.Exec(query, dargs)
-		dc.Unlock()
+		var resi driver.Result
+		withLock(dc, func() {
+			resi, err = ctxDriverExec(ctx, execer, query, dargs)
+		})
 		if err != driver.ErrSkip {
 			if err != nil {
 				return nil, err
@@ -1043,54 +1183,63 @@ func (db *DB) exec(query string, args []interface{}, strategy connReuseStrategy)
 		}
 	}
 
-	dc.Lock()
-	si, err := dc.ci.Prepare(query)
-	dc.Unlock()
+	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(driverStmt{dc, si}, args...)
+	ds := &driverStmt{Locker: dc, si: si}
+	defer ds.Close()
+	return resultFromStatement(ctx, ds, args...)
 }
 
-// Query executes a query that returns rows, typically a SELECT.
+// QueryContext 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) {
+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(query, args, cachedOrNewConn)
+		rows, err = db.query(ctx, query, args, cachedOrNewConn)
 		if err != driver.ErrBadConn {
 			break
 		}
 	}
 	if err == driver.ErrBadConn {
-		return db.query(query, args, alwaysNewConn)
+		return db.query(ctx, query, args, alwaysNewConn)
 	}
 	return rows, err
 }
 
-func (db *DB) query(query string, args []interface{}, strategy connReuseStrategy) (*Rows, error) {
-	ci, err := db.conn(strategy)
+// 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(ci, ci.releaseConn, query, args)
+	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(dc *driverConn, releaseConn func(error), query string, args []interface{}) (*Rows, error) {
+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
 		}
-		dc.Lock()
-		rowsi, err := queryer.Query(query, dargs)
-		dc.Unlock()
+		var rowsi driver.Rows
+		withLock(dc, func() {
+			rowsi, err = ctxDriverQuery(ctx, queryer, query, dargs)
+		})
 		if err != driver.ErrSkip {
 			if err != nil {
 				releaseConn(err)
@@ -1103,24 +1252,25 @@ func (db *DB) queryConn(dc *driverConn, releaseConn func(error), query string, a
 				releaseConn: releaseConn,
 				rowsi:       rowsi,
 			}
+			rows.initContextClose(ctx)
 			return rows, nil
 		}
 	}
 
-	dc.Lock()
-	si, err := dc.ci.Prepare(query)
-	dc.Unlock()
+	var si driver.Stmt
+	var err error
+	withLock(dc, func() {
+		si, err = ctxDriverPrepare(ctx, dc.ci, query)
+	})
 	if err != nil {
 		releaseConn(err)
 		return nil, err
 	}
 
-	ds := driverStmt{dc, si}
-	rowsi, err := rowsiFromStatement(ds, args...)
+	ds := &driverStmt{Locker: dc, si: si}
+	rowsi, err := rowsiFromStatement(ctx, ds, args...)
 	if err != nil {
-		dc.Lock()
-		si.Close()
-		dc.Unlock()
+		ds.Close()
 		releaseConn(err)
 		return nil, err
 	}
@@ -1131,53 +1281,93 @@ func (db *DB) queryConn(dc *driverConn, releaseConn func(error), query string, a
 		dc:          dc,
 		releaseConn: releaseConn,
 		rowsi:       rowsi,
-		closeStmt:   si,
+		closeStmt:   ds,
 	}
+	rows.initContextClose(ctx)
 	return rows, nil
 }
 
+// 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 {
-	rows, err := db.Query(query, args...)
-	return &Row{rows: rows, err: err}
+	return db.QueryRowContext(context.Background(), query, args...)
 }
 
-// Begin starts a transaction. The isolation level is dependent on
-// the driver.
-func (db *DB) Begin() (*Tx, error) {
+// BeginTx starts a transaction.
+//
+// The provided context is used until the transaction is committed or rolled back.
+// If the context is canceled, the sql package will roll back
+// the transaction. Tx.Commit will return an error if the context provided to
+// BeginTx is canceled.
+//
+// The provided TxOptions is optional and may be nil if defaults should be used.
+// If a non-default isolation level is used that the driver doesn't support,
+// an error will be returned.
+func (db *DB) BeginTx(ctx context.Context, opts *TxOptions) (*Tx, error) {
 	var tx *Tx
 	var err error
 	for i := 0; i < maxBadConnRetries; i++ {
-		tx, err = db.begin(cachedOrNewConn)
+		tx, err = db.begin(ctx, opts, cachedOrNewConn)
 		if err != driver.ErrBadConn {
 			break
 		}
 	}
 	if err == driver.ErrBadConn {
-		return db.begin(alwaysNewConn)
+		return db.begin(ctx, opts, alwaysNewConn)
 	}
 	return tx, err
 }
 
-func (db *DB) begin(strategy connReuseStrategy) (tx *Tx, err error) {
-	dc, err := db.conn(strategy)
+// Begin starts a transaction. The default isolation level is dependent on
+// the driver.
+func (db *DB) Begin() (*Tx, error) {
+	return db.BeginTx(context.Background(), nil)
+}
+
+func (db *DB) begin(ctx context.Context, opts *TxOptions, strategy connReuseStrategy) (tx *Tx, err error) {
+	dc, err := db.conn(ctx, strategy)
 	if err != nil {
 		return nil, err
 	}
-	dc.Lock()
-	txi, err := dc.ci.Begin()
-	dc.Unlock()
+	var txi driver.Tx
+	withLock(dc, func() {
+		txi, err = ctxDriverBegin(ctx, opts, dc.ci)
+	})
 	if err != nil {
 		db.putConn(dc, err)
 		return nil, err
 	}
-	return &Tx{
-		db:  db,
-		dc:  dc,
-		txi: txi,
-	}, nil
+
+	// 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,
+		ctx:    ctx,
+	}
+	go func(tx *Tx) {
+		select {
+		case <-tx.ctx.Done():
+			if !tx.isDone() {
+				// Discard and close the connection used to ensure the transaction
+				// is closed and the resources are released.
+				tx.rollback(true)
+			}
+		}
+	}(tx)
+	return tx, nil
 }
 
 // Driver returns the database's underlying driver.
@@ -1203,10 +1393,11 @@ type Tx struct {
 	dc  *driverConn
 	txi driver.Tx
 
-	// done transitions from false to true exactly once, on Commit
+	// done transitions from 0 to 1 exactly once, on Commit
 	// or Rollback. once done, all operations fail with
 	// ErrTxDone.
-	done bool
+	// Use atomic operations on value when checking value.
+	done int32
 
 	// All Stmts prepared for this transaction. These will be closed after the
 	// transaction has been committed or rolled back.
@@ -1214,22 +1405,33 @@ type Tx struct {
 		sync.Mutex
 		v []*Stmt
 	}
+
+	// cancel is called after done transitions from false to true.
+	cancel func()
+
+	// ctx lives for the life of the transaction.
+	ctx context.Context
+}
+
+func (tx *Tx) isDone() bool {
+	return atomic.LoadInt32(&tx.done) != 0
 }
 
+// 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")
 
+// close returns the connection to the pool and
+// must only be called by Tx.rollback or Tx.Commit.
 func (tx *Tx) close(err error) {
-	if tx.done {
-		panic("double close") // internal error
-	}
-	tx.done = true
 	tx.db.putConn(tx.dc, err)
+	tx.cancel()
 	tx.dc = nil
 	tx.txi = nil
 }
 
-func (tx *Tx) grabConn() (*driverConn, error) {
-	if tx.done {
+func (tx *Tx) grabConn(ctx context.Context) (*driverConn, error) {
+	if tx.isDone() {
 		return nil, ErrTxDone
 	}
 	return tx.dc, nil
@@ -1238,20 +1440,26 @@ func (tx *Tx) grabConn() (*driverConn, error) {
 // 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()
 	}
-	tx.stmts.Unlock()
 }
 
 // Commit commits the transaction.
 func (tx *Tx) Commit() error {
-	if tx.done {
+	if !atomic.CompareAndSwapInt32(&tx.done, 0, 1) {
 		return ErrTxDone
 	}
-	tx.dc.Lock()
-	err := tx.txi.Commit()
-	tx.dc.Unlock()
+	select {
+	default:
+	case <-tx.ctx.Done():
+		return tx.ctx.Err()
+	}
+	var err error
+	withLock(tx.dc, func() {
+		err = tx.txi.Commit()
+	})
 	if err != driver.ErrBadConn {
 		tx.closePrepared()
 	}
@@ -1259,28 +1467,42 @@ func (tx *Tx) Commit() error {
 	return err
 }
 
-// Rollback aborts the transaction.
-func (tx *Tx) Rollback() error {
-	if tx.done {
+// rollback aborts the transaction and optionally forces the pool to discard
+// the connection.
+func (tx *Tx) rollback(discardConn bool) error {
+	if !atomic.CompareAndSwapInt32(&tx.done, 0, 1) {
 		return ErrTxDone
 	}
-	tx.dc.Lock()
-	err := tx.txi.Rollback()
-	tx.dc.Unlock()
+	var err error
+	withLock(tx.dc, func() {
+		err = tx.txi.Rollback()
+	})
 	if err != driver.ErrBadConn {
 		tx.closePrepared()
 	}
+	if discardConn {
+		err = driver.ErrBadConn
+	}
 	tx.close(err)
 	return err
 }
 
+// Rollback aborts the transaction.
+func (tx *Tx) Rollback() error {
+	return tx.rollback(false)
+}
+
 // 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.
+// The returned statement operates within the transaction and will be closed
+// when 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) {
+//
+// 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
@@ -1294,14 +1516,15 @@ func (tx *Tx) Prepare(query string) (*Stmt, error) {
 	// 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.
-	dc, err := tx.grabConn()
+	dc, err := tx.grabConn(ctx)
 	if err != nil {
 		return nil, err
 	}
 
-	dc.Lock()
-	si, err := dc.ci.Prepare(query)
-	dc.Unlock()
+	var si driver.Stmt
+	withLock(dc, func() {
+		si, err = ctxDriverPrepare(ctx, dc.ci, query)
+	})
 	if err != nil {
 		return nil, err
 	}
@@ -1309,7 +1532,7 @@ func (tx *Tx) Prepare(query string) (*Stmt, error) {
 	stmt := &Stmt{
 		db: tx.db,
 		tx: tx,
-		txsi: &driverStmt{
+		txds: &driverStmt{
 			Locker: dc,
 			si:     si,
 		},
@@ -1321,7 +1544,17 @@ func (tx *Tx) Prepare(query string) (*Stmt, error) {
 	return stmt, nil
 }
 
-// Stmt returns a transaction-specific prepared statement from
+// 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:
@@ -1329,11 +1562,11 @@ func (tx *Tx) Prepare(query string) (*Stmt, error) {
 //  ...
 //  tx, err := db.Begin()
 //  ...
-//  res, err := tx.Stmt(updateMoney).Exec(123.45, 98293203)
+//  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) Stmt(stmt *Stmt) *Stmt {
+// The returned statement operates within the transaction and will be closed
+// when 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
@@ -1342,17 +1575,18 @@ func (tx *Tx) Stmt(stmt *Stmt) *Stmt {
 	if tx.db != stmt.db {
 		return &Stmt{stickyErr: errors.New("sql: Tx.Stmt: statement from different database used")}
 	}
-	dc, err := tx.grabConn()
+	dc, err := tx.grabConn(ctx)
 	if err != nil {
 		return &Stmt{stickyErr: err}
 	}
-	dc.Lock()
-	si, err := dc.ci.Prepare(stmt.query)
-	dc.Unlock()
+	var si driver.Stmt
+	withLock(dc, func() {
+		si, err = ctxDriverPrepare(ctx, dc.ci, stmt.query)
+	})
 	txs := &Stmt{
 		db: tx.db,
 		tx: tx,
-		txsi: &driverStmt{
+		txds: &driverStmt{
 			Locker: dc,
 			si:     si,
 		},
@@ -1365,10 +1599,26 @@ func (tx *Tx) Stmt(stmt *Stmt) *Stmt {
 	return txs
 }
 
-// Exec executes a query that doesn't return rows.
+// 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 will be closed
+// when 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) Exec(query string, args ...interface{}) (Result, error) {
-	dc, err := tx.grabConn()
+func (tx *Tx) ExecContext(ctx context.Context, query string, args ...interface{}) (Result, error) {
+	dc, err := tx.grabConn(ctx)
 	if err != nil {
 		return nil, err
 	}
@@ -1378,9 +1628,10 @@ func (tx *Tx) Exec(query string, args ...interface{}) (Result, error) {
 		if err != nil {
 			return nil, err
 		}
-		dc.Lock()
-		resi, err := execer.Exec(query, dargs)
-		dc.Unlock()
+		var resi driver.Result
+		withLock(dc, func() {
+			resi, err = ctxDriverExec(ctx, execer, query, dargs)
+		})
 		if err == nil {
 			return driverResult{dc, resi}, nil
 		}
@@ -1389,39 +1640,59 @@ func (tx *Tx) Exec(query string, args ...interface{}) (Result, error) {
 		}
 	}
 
-	dc.Lock()
-	si, err := dc.ci.Prepare(query)
-	dc.Unlock()
+	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() })
+	ds := &driverStmt{Locker: dc, si: si}
+	defer ds.Close()
 
-	return resultFromStatement(driverStmt{dc, si}, args...)
+	return resultFromStatement(ctx, ds, args...)
 }
 
-// Query executes a query that returns rows, typically a SELECT.
-func (tx *Tx) Query(query string, args ...interface{}) (*Rows, error) {
-	dc, err := tx.grabConn()
+// 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(dc, releaseConn, query, args)
+	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 {
-	rows, err := tx.Query(query, args...)
-	return &Row{rows: rows, err: err}
+	return tx.QueryRowContext(context.Background(), query, args...)
 }
 
 // connStmt is a prepared statement on a particular connection.
 type connStmt struct {
 	dc *driverConn
-	si driver.Stmt
+	ds *driverStmt
 }
 
 // Stmt is a prepared statement.
@@ -1436,7 +1707,7 @@ type Stmt struct {
 
 	// If in a transaction, else both nil:
 	tx   *Tx
-	txsi *driverStmt
+	txds *driverStmt
 
 	mu     sync.Mutex // protects the rest of the fields
 	closed bool
@@ -1452,15 +1723,15 @@ type Stmt struct {
 	lastNumClosed uint64
 }
 
-// Exec executes a prepared statement with the given arguments and
+// ExecContext 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) {
+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()
+		_, releaseConn, ds, err := s.connStmt(ctx)
 		if err != nil {
 			if err == driver.ErrBadConn {
 				continue
@@ -1468,7 +1739,7 @@ func (s *Stmt) Exec(args ...interface{}) (Result, error) {
 			return nil, err
 		}
 
-		res, err = resultFromStatement(driverStmt{dc, si}, args...)
+		res, err = resultFromStatement(ctx, ds, args...)
 		releaseConn(err)
 		if err != driver.ErrBadConn {
 			return res, err
@@ -1477,13 +1748,19 @@ func (s *Stmt) Exec(args ...interface{}) (Result, error) {
 	return nil, driver.ErrBadConn
 }
 
-func driverNumInput(ds driverStmt) int {
+// 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(ds driverStmt, args ...interface{}) (Result, error) {
+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
@@ -1493,14 +1770,15 @@ func resultFromStatement(ds driverStmt, args ...interface{}) (Result, error) {
 		return nil, fmt.Errorf("sql: expected %d arguments, got %d", want, len(args))
 	}
 
-	dargs, err := driverArgs(&ds, args)
+	dargs, err := driverArgs(ds, args)
 	if err != nil {
 		return nil, err
 	}
 
 	ds.Lock()
 	defer ds.Unlock()
-	resi, err := ds.si.Exec(dargs)
+
+	resi, err := ctxDriverStmtExec(ctx, ds.si, dargs)
 	if err != nil {
 		return nil, err
 	}
@@ -1536,7 +1814,7 @@ func (s *Stmt) removeClosedStmtLocked() {
 // 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() (ci *driverConn, releaseConn func(error), si driver.Stmt, err error) {
+func (s *Stmt) connStmt(ctx context.Context) (ci *driverConn, releaseConn func(error), ds *driverStmt, err error) {
 	if err = s.stickyErr; err != nil {
 		return
 	}
@@ -1551,19 +1829,18 @@ func (s *Stmt) connStmt() (ci *driverConn, releaseConn func(error), si driver.St
 	// transaction was created on.
 	if s.tx != nil {
 		s.mu.Unlock()
-		ci, err = s.tx.grabConn() // blocks, waiting for the connection.
+		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
+		return ci, releaseConn, s.txds, nil
 	}
 
 	s.removeClosedStmtLocked()
 	s.mu.Unlock()
 
-	// TODO(bradfitz): or always wait for one? make configurable later?
-	dc, err := s.db.conn(cachedOrNewConn)
+	dc, err := s.db.conn(ctx, cachedOrNewConn)
 	if err != nil {
 		return nil, nil, nil, err
 	}
@@ -1572,36 +1849,36 @@ func (s *Stmt) connStmt() (ci *driverConn, releaseConn func(error), si driver.St
 	for _, v := range s.css {
 		if v.dc == dc {
 			s.mu.Unlock()
-			return dc, dc.releaseConn, v.si, nil
+			return dc, dc.releaseConn, v.ds, nil
 		}
 	}
 	s.mu.Unlock()
 
 	// No luck; we need to prepare the statement on this connection
-	dc.Lock()
-	si, err = dc.prepareLocked(s.query)
-	dc.Unlock()
+	withLock(dc, func() {
+		ds, 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}
+	cs := connStmt{dc, ds}
 	s.css = append(s.css, cs)
 	s.mu.Unlock()
 
-	return dc, dc.releaseConn, si, nil
+	return dc, dc.releaseConn, ds, nil
 }
 
-// Query executes a prepared query statement with the given arguments
+// QueryContext 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) {
+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()
+		dc, releaseConn, ds, err := s.connStmt(ctx)
 		if err != nil {
 			if err == driver.ErrBadConn {
 				continue
@@ -1609,7 +1886,7 @@ func (s *Stmt) Query(args ...interface{}) (*Rows, error) {
 			return nil, err
 		}
 
-		rowsi, err = rowsiFromStatement(driverStmt{dc, si}, args...)
+		rowsi, err = rowsiFromStatement(ctx, ds, args...)
 		if err == nil {
 			// Note: ownership of ci passes to the *Rows, to be freed
 			// with releaseConn.
@@ -1618,6 +1895,7 @@ func (s *Stmt) Query(args ...interface{}) (*Rows, error) {
 				rowsi: rowsi,
 				// releaseConn set below
 			}
+			rows.initContextClose(ctx)
 			s.db.addDep(s, rows)
 			rows.releaseConn = func(err error) {
 				releaseConn(err)
@@ -1634,10 +1912,17 @@ func (s *Stmt) Query(args ...interface{}) (*Rows, error) {
 	return nil, driver.ErrBadConn
 }
 
-func rowsiFromStatement(ds driverStmt, args ...interface{}) (driver.Rows, error) {
-	ds.Lock()
-	want := ds.si.NumInput()
-	ds.Unlock()
+// 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
@@ -1646,21 +1931,22 @@ func rowsiFromStatement(ds driverStmt, args ...interface{}) (driver.Rows, error)
 		return nil, fmt.Errorf("sql: statement expects %d inputs; got %d", want, len(args))
 	}
 
-	dargs, err := driverArgs(&ds, args)
+	dargs, err := driverArgs(ds, args)
 	if err != nil {
 		return nil, err
 	}
 
 	ds.Lock()
-	rowsi, err := ds.si.Query(dargs)
-	ds.Unlock()
+	defer ds.Unlock()
+
+	rowsi, err := ctxDriverStmtQuery(ctx, ds.si, dargs)
 	if err != nil {
 		return nil, err
 	}
 	return rowsi, nil
 }
 
-// QueryRow executes a prepared query statement with the given arguments.
+// 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.
@@ -1670,15 +1956,30 @@ func rowsiFromStatement(ds driverStmt, args ...interface{}) (driver.Rows, error)
 // Example usage:
 //
 //  var name string
-//  err := nameByUseridStmt.QueryRow(id).Scan(&name)
-func (s *Stmt) QueryRow(args ...interface{}) *Row {
-	rows, err := s.Query(args...)
+//  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.
 func (s *Stmt) Close() error {
 	s.closemu.Lock()
@@ -1693,13 +1994,11 @@ func (s *Stmt) Close() error {
 		return nil
 	}
 	s.closed = true
+	s.mu.Unlock()
 
 	if s.tx != nil {
-		err := s.txsi.Close()
-		s.mu.Unlock()
-		return err
+		return s.txds.Close()
 	}
-	s.mu.Unlock()
 
 	return s.db.removeDep(s, s)
 }
@@ -1709,8 +2008,8 @@ func (s *Stmt) finalClose() error {
 	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.db.noteUnusedDriverStatement(v.dc, v.ds)
+			v.dc.removeOpenStmt(v.ds)
 		}
 		s.css = nil
 	}
@@ -1736,10 +2035,28 @@ type Rows struct {
 	releaseConn func(error)
 	rowsi       driver.Rows
 
-	closed    bool
+	// 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.
 	lastcols  []driver.Value
 	lasterr   error       // non-nil only if closed is true
-	closeStmt driver.Stmt // if non-nil, statement to Close on close
+	closeStmt *driverStmt // 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
@@ -1749,7 +2066,7 @@ type Rows struct {
 //
 // Every call to Scan, even the first one, must be preceded by a call to Next.
 func (rs *Rows) Next() bool {
-	if rs.closed {
+	if rs.isClosed() {
 		return false
 	}
 	if rs.lastcols == nil {
@@ -1757,6 +2074,47 @@ func (rs *Rows) Next() bool {
 	}
 	rs.lasterr = rs.rowsi.Next(rs.lastcols)
 	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 further 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
+	nextResultSet, ok := rs.rowsi.(driver.RowsNextResultSet)
+	if !ok {
+		rs.Close()
+		return false
+	}
+	rs.lasterr = nextResultSet.NextResultSet()
+	if rs.lasterr != nil {
 		rs.Close()
 		return false
 	}
@@ -1776,7 +2134,7 @@ func (rs *Rows) Err() error {
 // Columns returns an error if the rows are closed, or if the rows
 // are from QueryRow and there was a deferred error.
 func (rs *Rows) Columns() ([]string, error) {
-	if rs.closed {
+	if rs.isClosed() {
 		return nil, errors.New("sql: Rows are closed")
 	}
 	if rs.rowsi == nil {
@@ -1785,6 +2143,107 @@ func (rs *Rows) Columns() ([]string, error) {
 	return rs.rowsi.Columns(), nil
 }
 
+// ColumnTypes returns column information such as column type, length,
+// and nullable. Some information may not be available from some drivers.
+func (rs *Rows) ColumnTypes() ([]*ColumnType, error) {
+	if rs.isClosed() {
+		return nil, errors.New("sql: Rows are closed")
+	}
+	if rs.rowsi == nil {
+		return nil, errors.New("sql: no Rows available")
+	}
+	return rowsColumnInfoSetup(rs.rowsi), nil
+}
+
+// ColumnType contains the name and type of a column.
+type ColumnType struct {
+	name string
+
+	hasNullable       bool
+	hasLength         bool
+	hasPrecisionScale bool
+
+	nullable     bool
+	length       int64
+	databaseType string
+	precision    int64
+	scale        int64
+	scanType     reflect.Type
+}
+
+// Name returns the name or alias of the column.
+func (ci *ColumnType) Name() string {
+	return ci.name
+}
+
+// Length returns the column type length for variable length column types such
+// as text and binary field types. If the type length is unbounded the value will
+// be math.MaxInt64 (any database limits will still apply).
+// If the column type is not variable length, such as an int, or if not supported
+// by the driver ok is false.
+func (ci *ColumnType) Length() (length int64, ok bool) {
+	return ci.length, ci.hasLength
+}
+
+// DecimalSize returns the scale and precision of a decimal type.
+// If not applicable or if not supported ok is false.
+func (ci *ColumnType) DecimalSize() (precision, scale int64, ok bool) {
+	return ci.precision, ci.scale, ci.hasPrecisionScale
+}
+
+// ScanType returns a Go type suitable for scanning into using Rows.Scan.
+// If a driver does not support this property ScanType will return
+// the type of an empty interface.
+func (ci *ColumnType) ScanType() reflect.Type {
+	return ci.scanType
+}
+
+// Nullable returns whether the column may be null.
+// If a driver does not support this property ok will be false.
+func (ci *ColumnType) Nullable() (nullable, ok bool) {
+	return ci.nullable, ci.hasNullable
+}
+
+// DatabaseTypeName returns the database system name of the column type. If an empty
+// string is returned the driver type name is not supported.
+// Consult your driver documentation for a list of driver data types. Length specifiers
+// are not included.
+// Common type include "VARCHAR", "TEXT", "NVARCHAR", "DECIMAL", "BOOL", "INT", "BIGINT".
+func (ci *ColumnType) DatabaseTypeName() string {
+	return ci.databaseType
+}
+
+func rowsColumnInfoSetup(rowsi driver.Rows) []*ColumnType {
+	names := rowsi.Columns()
+
+	list := make([]*ColumnType, len(names))
+	for i := range list {
+		ci := &ColumnType{
+			name: names[i],
+		}
+		list[i] = ci
+
+		if prop, ok := rowsi.(driver.RowsColumnTypeScanType); ok {
+			ci.scanType = prop.ColumnTypeScanType(i)
+		} else {
+			ci.scanType = reflect.TypeOf(new(interface{})).Elem()
+		}
+		if prop, ok := rowsi.(driver.RowsColumnTypeDatabaseTypeName); ok {
+			ci.databaseType = prop.ColumnTypeDatabaseTypeName(i)
+		}
+		if prop, ok := rowsi.(driver.RowsColumnTypeLength); ok {
+			ci.length, ci.hasLength = prop.ColumnTypeLength(i)
+		}
+		if prop, ok := rowsi.(driver.RowsColumnTypeNullable); ok {
+			ci.nullable, ci.hasNullable = prop.ColumnTypeNullable(i)
+		}
+		if prop, ok := rowsi.(driver.RowsColumnTypePrecisionScale); ok {
+			ci.precision, ci.scale, ci.hasPrecisionScale = prop.ColumnTypePrecisionScale(i)
+		}
+	}
+	return list
+}
+
 // Scan copies the columns in the current row into the values pointed
 // at by dest. The number of values in dest must be the same as the
 // number of columns in Rows.
@@ -1837,7 +2296,7 @@ func (rs *Rows) Columns() ([]string, error) {
 // For scanning into *bool, the source may be true, false, 1, 0, or
 // string inputs parseable by strconv.ParseBool.
 func (rs *Rows) Scan(dest ...interface{}) error {
-	if rs.closed {
+	if rs.isClosed() {
 		return errors.New("sql: Rows are closed")
 	}
 	if rs.lastcols == nil {
@@ -1857,14 +2316,21 @@ func (rs *Rows) Scan(dest ...interface{}) error {
 
 var rowsCloseHook func(*Rows, *error)
 
-// Close closes the Rows, preventing further enumeration. If Next returns
-// false, the Rows are closed automatically and it will suffice to check the
+func (rs *Rows) isClosed() bool {
+	return atomic.LoadInt32(&rs.closed) != 0
+}
+
+// Close closes the Rows, preventing further enumeration. If Next is called
+// and returns false and there are no further result sets,
+// the Rows are closed automatically and it will suffice to check the
 // result of Err. Close is idempotent and does not affect the result of Err.
 func (rs *Rows) Close() error {
-	if rs.closed {
+	if !atomic.CompareAndSwapInt32(&rs.closed, 0, 1) {
 		return nil
 	}
-	rs.closed = true
+	if rs.ctxClose != nil {
+		close(rs.ctxClose)
+	}
 	err := rs.rowsi.Close()
 	if fn := rowsCloseHook; fn != nil {
 		fn(rs, &err)
author	Ian Lance Taylor <iant@golang.org>	2017-01-14 00:05:42 +0000
committer	Ian Lance Taylor <ian@gcc.gnu.org>	2017-01-14 00:05:42 +0000
commit	c2047754c300b68c05d65faa8dc2925fe67b71b4 (patch)
tree	e183ae81a1f48a02945cb6de463a70c5be1b06f6 /libgo/go/database/sql/sql.go
parent	829afb8f05602bb31c9c597b24df7377fed4f059 (diff)
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