-
Notifications
You must be signed in to change notification settings - Fork 17.5k
/
driver.go
553 lines (495 loc) · 20.9 KB
/
driver.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package driver defines interfaces to be implemented by database
// drivers as used by package sql.
//
// Most code should use the [database/sql] package.
//
// The driver interface has evolved over time. Drivers should implement
// [Connector] and [DriverContext] interfaces.
// The Connector.Connect and Driver.Open methods should never return [ErrBadConn].
// [ErrBadConn] should only be returned from [Validator], [SessionResetter], or
// a query method if the connection is already in an invalid (e.g. closed) state.
//
// All [Conn] implementations should implement the following interfaces:
// [Pinger], [SessionResetter], and [Validator].
//
// If named parameters or context are supported, the driver's [Conn] should implement:
// [ExecerContext], [QueryerContext], [ConnPrepareContext], and [ConnBeginTx].
//
// To support custom data types, implement [NamedValueChecker]. [NamedValueChecker]
// also allows queries to accept per-query options as a parameter by returning
// [ErrRemoveArgument] from CheckNamedValue.
//
// If multiple result sets are supported, [Rows] should implement [RowsNextResultSet].
// If the driver knows how to describe the types present in the returned result
// it should implement the following interfaces: [RowsColumnTypeScanType],
// [RowsColumnTypeDatabaseTypeName], [RowsColumnTypeLength], [RowsColumnTypeNullable],
// and [RowsColumnTypePrecisionScale]. A given row value may also return a [Rows]
// type, which may represent a database cursor value.
//
// If a [Conn] implements [Validator], then the IsValid method is called
// before returning the connection to the connection pool. If an entry in the
// connection pool implements [SessionResetter], then ResetSession
// is called before reusing the connection for another query. If a connection is
// never returned to the connection pool but is immediately reused, then
// ResetSession is called prior to reuse but IsValid is not called.
package driver
import (
"context"
"errors"
"reflect"
)
// Value is a value that drivers must be able to handle.
// It is either nil, a type handled by a database driver's [NamedValueChecker]
// interface, or an instance of one of these types:
//
// int64
// float64
// bool
// []byte
// string
// time.Time
//
// If the driver supports cursors, a returned Value may also implement the [Rows] interface
// in this package. This is used, for example, when a user selects a cursor
// such as "select cursor(select * from my_table) from dual". If the [Rows]
// from the select is closed, the cursor [Rows] will also be closed.
type Value any
// NamedValue holds both the value name and value.
type NamedValue struct {
// If the Name is not empty it should be used for the parameter identifier and
// not the ordinal position.
//
// Name will not have a symbol prefix.
Name string
// Ordinal position of the parameter starting from one and is always set.
Ordinal int
// Value is the parameter value.
Value Value
}
// Driver is the interface that must be implemented by a database
// driver.
//
// Database drivers may implement [DriverContext] for access
// to contexts and to parse the name only once for a pool of connections,
// instead of once per connection.
type Driver interface {
// Open returns a new connection to the database.
// The name is a string in a driver-specific format.
//
// Open may return a cached connection (one previously
// closed), but doing so is unnecessary; the sql package
// maintains a pool of idle connections for efficient re-use.
//
// The returned connection is only used by one goroutine at a
// time.
Open(name string) (Conn, error)
}
// If a [Driver] implements DriverContext, then [database/sql.DB] will call
// OpenConnector to obtain a [Connector] and then invoke
// that [Connector]'s Connect method to obtain each needed connection,
// instead of invoking the [Driver]'s Open method for each connection.
// The two-step sequence allows drivers to parse the name just once
// and also provides access to per-[Conn] contexts.
type DriverContext interface {
// OpenConnector must parse the name in the same format that Driver.Open
// parses the name parameter.
OpenConnector(name string) (Connector, error)
}
// A Connector represents a driver in a fixed configuration
// and can create any number of equivalent Conns for use
// by multiple goroutines.
//
// A Connector can be passed to [database/sql.OpenDB], to allow drivers
// to implement their own [database/sql.DB] constructors, or returned by
// [DriverContext]'s OpenConnector method, to allow drivers
// access to context and to avoid repeated parsing of driver
// configuration.
//
// If a Connector implements [io.Closer], the [database/sql.DB.Close]
// method will call the Close method and return error (if any).
type Connector interface {
// Connect returns a connection to the database.
// Connect may return a cached connection (one previously
// closed), but doing so is unnecessary; the sql package
// maintains a pool of idle connections for efficient re-use.
//
// The provided context.Context is for dialing purposes only
// (see net.DialContext) and should not be stored or used for
// other purposes. A default timeout should still be used
// when dialing as a connection pool may call Connect
// asynchronously to any query.
//
// The returned connection is only used by one goroutine at a
// time.
Connect(context.Context) (Conn, error)
// Driver returns the underlying Driver of the Connector,
// mainly to maintain compatibility with the Driver method
// on sql.DB.
Driver() Driver
}
// ErrSkip may be returned by some optional interfaces' methods to
// indicate at runtime that the fast path is unavailable and the sql
// package should continue as if the optional interface was not
// implemented. ErrSkip is only supported where explicitly
// documented.
var ErrSkip = errors.New("driver: skip fast-path; continue as if unimplemented")
// ErrBadConn should be returned by a driver to signal to the [database/sql]
// package that a driver.[Conn] is in a bad state (such as the server
// having earlier closed the connection) and the [database/sql] package should
// retry on a new connection.
//
// To prevent duplicate operations, ErrBadConn should NOT be returned
// if there's a possibility that the database server might have
// performed the operation. Even if the server sends back an error,
// you shouldn't return ErrBadConn.
//
// Errors will be checked using [errors.Is]. An error may
// wrap ErrBadConn or implement the Is(error) bool method.
var ErrBadConn = errors.New("driver: bad connection")
// Pinger is an optional interface that may be implemented by a [Conn].
//
// If a [Conn] does not implement Pinger, the [database/sql.DB.Ping] and
// [database/sql.DB.PingContext] will check if there is at least one [Conn] available.
//
// If Conn.Ping returns [ErrBadConn], [database/sql.DB.Ping] and [database/sql.DB.PingContext] will remove
// the [Conn] from pool.
type Pinger interface {
Ping(ctx context.Context) error
}
// Execer is an optional interface that may be implemented by a [Conn].
//
// If a [Conn] implements neither [ExecerContext] nor [Execer],
// the [database/sql.DB.Exec] will first prepare a query, execute the statement,
// and then close the statement.
//
// Exec may return [ErrSkip].
//
// Deprecated: Drivers should implement [ExecerContext] instead.
type Execer interface {
Exec(query string, args []Value) (Result, error)
}
// ExecerContext is an optional interface that may be implemented by a [Conn].
//
// If a [Conn] does not implement [ExecerContext], the [database/sql.DB.Exec]
// will fall back to [Execer]; if the Conn does not implement Execer either,
// [database/sql.DB.Exec] will first prepare a query, execute the statement, and then
// close the statement.
//
// ExecContext may return [ErrSkip].
//
// ExecContext must honor the context timeout and return when the context is canceled.
type ExecerContext interface {
ExecContext(ctx context.Context, query string, args []NamedValue) (Result, error)
}
// Queryer is an optional interface that may be implemented by a [Conn].
//
// If a [Conn] implements neither [QueryerContext] nor [Queryer],
// the [database/sql.DB.Query] will first prepare a query, execute the statement,
// and then close the statement.
//
// Query may return [ErrSkip].
//
// Deprecated: Drivers should implement [QueryerContext] instead.
type Queryer interface {
Query(query string, args []Value) (Rows, error)
}
// QueryerContext is an optional interface that may be implemented by a [Conn].
//
// If a [Conn] does not implement QueryerContext, the [database/sql.DB.Query]
// will fall back to [Queryer]; if the [Conn] does not implement [Queryer] either,
// [database/sql.DB.Query] will first prepare a query, execute the statement, and then
// close the statement.
//
// QueryContext may return [ErrSkip].
//
// QueryContext must honor the context timeout and return when the context is canceled.
type QueryerContext interface {
QueryContext(ctx context.Context, query string, args []NamedValue) (Rows, error)
}
// Conn is a connection to a database. It is not used concurrently
// by multiple goroutines.
//
// Conn is assumed to be stateful.
type Conn interface {
// Prepare returns a prepared statement, bound to this connection.
Prepare(query string) (Stmt, error)
// Close invalidates and potentially stops any current
// prepared statements and transactions, marking this
// connection as no longer in use.
//
// Because the sql package maintains a free pool of
// connections and only calls Close when there's a surplus of
// idle connections, it shouldn't be necessary for drivers to
// do their own connection caching.
//
// Drivers must ensure all network calls made by Close
// do not block indefinitely (e.g. apply a timeout).
Close() error
// Begin starts and returns a new transaction.
//
// Deprecated: Drivers should implement ConnBeginTx instead (or additionally).
Begin() (Tx, error)
}
// ConnPrepareContext enhances the [Conn] interface with context.
type ConnPrepareContext interface {
// PrepareContext returns a prepared statement, bound to this connection.
// context is for the preparation of the statement,
// it must not store the context within the statement itself.
PrepareContext(ctx context.Context, query string) (Stmt, error)
}
// IsolationLevel is the transaction isolation level stored in [TxOptions].
//
// This type should be considered identical to [database/sql.IsolationLevel] along
// with any values defined on it.
type IsolationLevel int
// TxOptions holds the transaction options.
//
// This type should be considered identical to [database/sql.TxOptions].
type TxOptions struct {
Isolation IsolationLevel
ReadOnly bool
}
// ConnBeginTx enhances the [Conn] interface with context and [TxOptions].
type ConnBeginTx interface {
// BeginTx starts and returns a new transaction.
// If the context is canceled by the user the sql package will
// call Tx.Rollback before discarding and closing the connection.
//
// This must check opts.Isolation to determine if there is a set
// isolation level. If the driver does not support a non-default
// level and one is set or if there is a non-default isolation level
// that is not supported, an error must be returned.
//
// This must also check opts.ReadOnly to determine if the read-only
// value is true to either set the read-only transaction property if supported
// or return an error if it is not supported.
BeginTx(ctx context.Context, opts TxOptions) (Tx, error)
}
// SessionResetter may be implemented by [Conn] to allow drivers to reset the
// session state associated with the connection and to signal a bad connection.
type SessionResetter interface {
// ResetSession is called prior to executing a query on the connection
// if the connection has been used before. If the driver returns ErrBadConn
// the connection is discarded.
ResetSession(ctx context.Context) error
}
// Validator may be implemented by [Conn] to allow drivers to
// signal if a connection is valid or if it should be discarded.
//
// If implemented, drivers may return the underlying error from queries,
// even if the connection should be discarded by the connection pool.
type Validator interface {
// IsValid is called prior to placing the connection into the
// connection pool. The connection will be discarded if false is returned.
IsValid() bool
}
// Result is the result of a query execution.
type Result interface {
// LastInsertId returns the database's auto-generated ID
// after, for example, an INSERT into a table with primary
// key.
LastInsertId() (int64, error)
// RowsAffected returns the number of rows affected by the
// query.
RowsAffected() (int64, error)
}
// Stmt is a prepared statement. It is bound to a [Conn] and not
// used by multiple goroutines concurrently.
type Stmt interface {
// Close closes the statement.
//
// As of Go 1.1, a Stmt will not be closed if it's in use
// by any queries.
//
// Drivers must ensure all network calls made by Close
// do not block indefinitely (e.g. apply a timeout).
Close() error
// NumInput returns the number of placeholder parameters.
//
// If NumInput returns >= 0, the sql package will sanity check
// argument counts from callers and return errors to the caller
// before the statement's Exec or Query methods are called.
//
// NumInput may also return -1, if the driver doesn't know
// its number of placeholders. In that case, the sql package
// will not sanity check Exec or Query argument counts.
NumInput() int
// Exec executes a query that doesn't return rows, such
// as an INSERT or UPDATE.
//
// Deprecated: Drivers should implement StmtExecContext instead (or additionally).
Exec(args []Value) (Result, error)
// Query executes a query that may return rows, such as a
// SELECT.
//
// Deprecated: Drivers should implement StmtQueryContext instead (or additionally).
Query(args []Value) (Rows, error)
}
// StmtExecContext enhances the [Stmt] interface by providing Exec with context.
type StmtExecContext interface {
// ExecContext executes a query that doesn't return rows, such
// as an INSERT or UPDATE.
//
// ExecContext must honor the context timeout and return when it is canceled.
ExecContext(ctx context.Context, args []NamedValue) (Result, error)
}
// StmtQueryContext enhances the [Stmt] interface by providing Query with context.
type StmtQueryContext interface {
// QueryContext executes a query that may return rows, such as a
// SELECT.
//
// QueryContext must honor the context timeout and return when it is canceled.
QueryContext(ctx context.Context, args []NamedValue) (Rows, error)
}
// ErrRemoveArgument may be returned from [NamedValueChecker] to instruct the
// [database/sql] package to not pass the argument to the driver query interface.
// Return when accepting query specific options or structures that aren't
// SQL query arguments.
var ErrRemoveArgument = errors.New("driver: remove argument from query")
// NamedValueChecker may be optionally implemented by [Conn] or [Stmt]. It provides
// the driver more control to handle Go and database types beyond the default
// [Value] types allowed.
//
// The [database/sql] package checks for value checkers in the following order,
// stopping at the first found match: Stmt.NamedValueChecker, Conn.NamedValueChecker,
// Stmt.ColumnConverter, [DefaultParameterConverter].
//
// If CheckNamedValue returns [ErrRemoveArgument], the [NamedValue] will not be included in
// the final query arguments. This may be used to pass special options to
// the query itself.
//
// If [ErrSkip] is returned the column converter error checking
// path is used for the argument. Drivers may wish to return [ErrSkip] after
// they have exhausted their own special cases.
type NamedValueChecker interface {
// CheckNamedValue is called before passing arguments to the driver
// and is called in place of any ColumnConverter. CheckNamedValue must do type
// validation and conversion as appropriate for the driver.
CheckNamedValue(*NamedValue) error
}
// ColumnConverter may be optionally implemented by [Stmt] if the
// statement is aware of its own columns' types and can convert from
// any type to a driver [Value].
//
// Deprecated: Drivers should implement [NamedValueChecker].
type ColumnConverter interface {
// ColumnConverter returns a ValueConverter for the provided
// column index. If the type of a specific column isn't known
// or shouldn't be handled specially, [DefaultParameterConverter]
// can be returned.
ColumnConverter(idx int) ValueConverter
}
// Rows is an iterator over an executed query's results.
type Rows interface {
// Columns returns the names of the columns. The number of
// columns of the result is inferred from the length of the
// slice. If a particular column name isn't known, an empty
// string should be returned for that entry.
Columns() []string
// Close closes the rows iterator.
Close() error
// Next is called to populate the next row of data into
// the provided slice. The provided slice will be the same
// size as the Columns() are wide.
//
// Next should return io.EOF when there are no more rows.
//
// The dest should not be written to outside of Next. Care
// should be taken when closing Rows not to modify
// a buffer held in dest.
Next(dest []Value) error
}
// RowsNextResultSet extends the [Rows] interface by providing a way to signal
// the driver to advance to the next result set.
type RowsNextResultSet interface {
Rows
// HasNextResultSet is called at the end of the current result set and
// reports whether there is another result set after the current one.
HasNextResultSet() bool
// NextResultSet advances the driver to the next result set even
// if there are remaining rows in the current result set.
//
// NextResultSet should return io.EOF when there are no more result sets.
NextResultSet() error
}
// RowsColumnTypeScanType may be implemented by [Rows]. It should return
// the value type that can be used to scan types into. For example, the database
// column type "bigint" this should return "[reflect.TypeOf](int64(0))".
type RowsColumnTypeScanType interface {
Rows
ColumnTypeScanType(index int) reflect.Type
}
// RowsColumnTypeDatabaseTypeName may be implemented by [Rows]. It should return the
// database system type name without the length. Type names should be uppercase.
// Examples of returned types: "VARCHAR", "NVARCHAR", "VARCHAR2", "CHAR", "TEXT",
// "DECIMAL", "SMALLINT", "INT", "BIGINT", "BOOL", "[]BIGINT", "JSONB", "XML",
// "TIMESTAMP".
type RowsColumnTypeDatabaseTypeName interface {
Rows
ColumnTypeDatabaseTypeName(index int) string
}
// RowsColumnTypeLength may be implemented by [Rows]. It should return the length
// of the column type if the column is a variable length type. If the column is
// not a variable length type ok should return false.
// If length is not limited other than system limits, it should return [math.MaxInt64].
// The following are examples of returned values for various types:
//
// TEXT (math.MaxInt64, true)
// varchar(10) (10, true)
// nvarchar(10) (10, true)
// decimal (0, false)
// int (0, false)
// bytea(30) (30, true)
type RowsColumnTypeLength interface {
Rows
ColumnTypeLength(index int) (length int64, ok bool)
}
// RowsColumnTypeNullable may be implemented by [Rows]. The nullable value should
// be true if it is known the column may be null, or false if the column is known
// to be not nullable.
// If the column nullability is unknown, ok should be false.
type RowsColumnTypeNullable interface {
Rows
ColumnTypeNullable(index int) (nullable, ok bool)
}
// RowsColumnTypePrecisionScale may be implemented by [Rows]. It should return
// the precision and scale for decimal types. If not applicable, ok should be false.
// The following are examples of returned values for various types:
//
// decimal(38, 4) (38, 4, true)
// int (0, 0, false)
// decimal (math.MaxInt64, math.MaxInt64, true)
type RowsColumnTypePrecisionScale interface {
Rows
ColumnTypePrecisionScale(index int) (precision, scale int64, ok bool)
}
// Tx is a transaction.
type Tx interface {
Commit() error
Rollback() error
}
// RowsAffected implements [Result] for an INSERT or UPDATE operation
// which mutates a number of rows.
type RowsAffected int64
var _ Result = RowsAffected(0)
func (RowsAffected) LastInsertId() (int64, error) {
return 0, errors.New("LastInsertId is not supported by this driver")
}
func (v RowsAffected) RowsAffected() (int64, error) {
return int64(v), nil
}
// ResultNoRows is a pre-defined [Result] for drivers to return when a DDL
// command (such as a CREATE TABLE) succeeds. It returns an error for both
// LastInsertId and [RowsAffected].
var ResultNoRows noRows
type noRows struct{}
var _ Result = noRows{}
func (noRows) LastInsertId() (int64, error) {
return 0, errors.New("no LastInsertId available after DDL statement")
}
func (noRows) RowsAffected() (int64, error) {
return 0, errors.New("no RowsAffected available after DDL statement")
}