-
Notifications
You must be signed in to change notification settings - Fork 59
/
txn.go
404 lines (368 loc) · 11.2 KB
/
txn.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
package lmdb
/*
#include <stdlib.h>
#include <stdio.h>
#include "lmdb.h"
#include "lmdbgo.h"
*/
import "C"
import (
"log"
"runtime"
"unsafe"
)
// This flags are used exclusively for Txn.OpenDBI and Txn.OpenRoot. The
// Create flag must always be supplied when opening a non-root DBI for the
// first time.
//
// BUG(bmatsuo):
// MDB_INTEGERKEY and MDB_INTEGERDUP aren't usable. I'm not sure they would be
// faster with the cgo bridge. They need to be tested and benchmarked.
const (
// Flags for Txn.OpenDBI.
ReverseKey = C.MDB_REVERSEKEY // Use reverse string keys.
DupSort = C.MDB_DUPSORT // Use sorted duplicates.
DupFixed = C.MDB_DUPFIXED // Duplicate items have a fixed size (DupSort).
ReverseDup = C.MDB_REVERSEDUP // Reverse duplicate values (DupSort).
Create = C.MDB_CREATE // Create DB if not already existing.
)
// Txn is a database transaction in an environment.
//
// WARNING: A writable Txn is not threadsafe and may only be used in the
// goroutine that created it.
//
// See MDB_txn.
type Txn struct {
// If RawRead is true []byte values retrieved from Get() calls on the Txn
// and its cursors will point directly into the memory-mapped structure.
// Such slices will be readonly and must only be referenced wthin the
// transaction's lifetime.
RawRead bool
managed bool
readonly bool
env *Env
_txn *C.MDB_txn
errLogf func(format string, v ...interface{})
key *C.MDB_val
val *C.MDB_val
}
// beginTxn does not lock the OS thread which is a prerequisite for creating a
// write transaction.
func beginTxn(env *Env, parent *Txn, flags uint) (*Txn, error) {
txn := &Txn{
readonly: (flags&Readonly != 0),
env: env,
}
var ptxn *C.MDB_txn
if parent == nil {
ptxn = nil
txn.key = new(C.MDB_val)
txn.val = new(C.MDB_val)
} else {
ptxn = parent._txn
txn.key = parent.key
txn.val = parent.val
}
ret := C.mdb_txn_begin(env._env, ptxn, C.uint(flags), &txn._txn)
if ret != success {
return nil, operrno("mdb_txn_begin", ret)
}
return txn, nil
}
// ID returns the identifier for txn. A view transaction identifier
// corresponds to the Env snapshot being viewed and may be shared with other
// view transactions.
//
// See mdb_txn_id.
func (txn *Txn) ID() uintptr {
return uintptr(C.mdb_txn_id(txn._txn))
}
// Commit persists all transaction operations to the database and clears the
// finalizer on txn. A Txn cannot be used again after Commit is called.
//
// See mdb_txn_commit.
func (txn *Txn) Commit() error {
if txn.managed {
panic("managed transaction cannot be comitted directly")
}
runtime.SetFinalizer(txn, nil)
return txn.commit()
}
func (txn *Txn) commit() error {
ret := C.mdb_txn_commit(txn._txn)
txn._txn = nil
return operrno("mdb_txn_commit", ret)
}
// Abort discards pending writes in the transaction and clears the finalizer on
// txn. A Txn cannot be used again after Abort is called.
//
// See mdb_txn_abort.
func (txn *Txn) Abort() {
if txn.managed {
panic("managed transaction cannot be aborted directly")
}
runtime.SetFinalizer(txn, nil)
txn.abort()
}
func (txn *Txn) abort() {
if txn._txn == nil {
return
}
C.mdb_txn_abort(txn._txn)
// The transaction handle is always freed.
txn._txn = nil
}
// Reset aborts the transaction clears internal state so the transaction may be
// reused by calling Renew. If txn is not going to be reused txn.Abort() must
// be called to release its slot in the lock table and free its memory. Reset
// panics if txn is managed by Update, View, etc.
//
// See mdb_txn_reset.
func (txn *Txn) Reset() {
if txn.managed {
panic("managed transaction cannot be reset directly")
}
txn.reset()
runtime.SetFinalizer(txn, nil)
}
func (txn *Txn) reset() {
C.mdb_txn_reset(txn._txn)
}
// Renew reuses a transaction that was previously reset by calling txn.Reset().
// Renew panics if txn is managed by Update, View, etc.
//
// See mdb_txn_renew.
func (txn *Txn) Renew() error {
if txn.managed {
panic("managed transaction cannot be renewed directly")
}
err := txn.renew()
if err != nil {
return err
}
runtime.SetFinalizer(txn, func(v interface{}) { v.(*Txn).finalize() })
return nil
}
func (txn *Txn) renew() error {
ret := C.mdb_txn_renew(txn._txn)
return operrno("mdb_txn_renew", ret)
}
// OpenDBI opens a named database in the environment. An error is returned if
// name is empty. The DBI returned by OpenDBI can be used in other
// transactions but not before Txn has terminated.
//
// OpenDBI can only be called after env.SetMaxDBs() has been called to set the
// maximum number of named databases.
//
// The C API uses null terminated strings for database names. A consequence is
// that names cannot contain null bytes themselves. OpenDBI does not check for
// null bytes in the name argument.
//
// See mdb_dbi_open.
func (txn *Txn) OpenDBI(name string, flags uint) (DBI, error) {
cname := C.CString(name)
dbi, err := txn.openDBI(cname, flags)
C.free(unsafe.Pointer(cname))
return dbi, err
}
// CreateDBI is a shorthand for OpenDBI that passed the flag lmdb.Create.
func (txn *Txn) CreateDBI(name string) (DBI, error) {
return txn.OpenDBI(name, Create)
}
// Flags returns the database flags for handle dbi.
func (txn *Txn) Flags(dbi DBI) (uint, error) {
var cflags C.uint
ret := C.mdb_dbi_flags(txn._txn, C.MDB_dbi(dbi), (*C.uint)(&cflags))
return uint(cflags), operrno("mdb_dbi_flags", ret)
}
// OpenRoot opens the root database. OpenRoot behaves similarly to OpenDBI but
// does not require env.SetMaxDBs() to be called beforehand. And, OpenRoot can
// be called without flags in a View transaction.
func (txn *Txn) OpenRoot(flags uint) (DBI, error) {
return txn.openDBI(nil, flags)
}
// openDBI returns returns whatever DBI value was set by mdb_open_dbi. In an
// error case, LMDB does not currently set DBI in case of failure, so zero is
// returned in those cases. This is not a big deal for now because
// applications are expected to handle any error encountered opening a
// database.
func (txn *Txn) openDBI(cname *C.char, flags uint) (DBI, error) {
var dbi C.MDB_dbi
ret := C.mdb_dbi_open(txn._txn, cname, C.uint(flags), &dbi)
return DBI(dbi), operrno("mdb_dbi_open", ret)
}
// Stat returns a Stat describing the database dbi.
//
// See mdb_stat.
func (txn *Txn) Stat(dbi DBI) (*Stat, error) {
var _stat C.MDB_stat
ret := C.mdb_stat(txn._txn, C.MDB_dbi(dbi), &_stat)
if ret != success {
return nil, operrno("mdb_stat", ret)
}
stat := Stat{PSize: uint(_stat.ms_psize),
Depth: uint(_stat.ms_depth),
BranchPages: uint64(_stat.ms_branch_pages),
LeafPages: uint64(_stat.ms_leaf_pages),
OverflowPages: uint64(_stat.ms_overflow_pages),
Entries: uint64(_stat.ms_entries)}
return &stat, nil
}
// Drop empties the database if del is false. Drop deletes and closes the
// database if del is true.
//
// See mdb_drop.
func (txn *Txn) Drop(dbi DBI, del bool) error {
ret := C.mdb_drop(txn._txn, C.MDB_dbi(dbi), cbool(del))
return operrno("mdb_drop", ret)
}
// Sub executes fn in a subtransaction. Sub commits the subtransaction iff a
// nil error is returned by fn and otherwise aborts it. Sub returns any error
// it encounters.
//
// Sub may only be called on an Update Txn (one created without the Readonly
// flag). Calling Sub on a View transaction will return an error. Sub assumes
// the calling goroutine is locked to an OS thread and will not call
// runtime.LockOSThread.
//
// Any call to Abort, Commit, Renew, or Reset on a Txn created by Sub will
// panic.
func (txn *Txn) Sub(fn TxnOp) error {
// As of 0.9.14 Readonly is the only Txn flag and readonly subtransactions
// don't make sense.
return txn.subFlag(0, fn)
}
func (txn *Txn) subFlag(flags uint, fn TxnOp) error {
sub, err := beginTxn(txn.env, txn, flags)
if err != nil {
return err
}
sub.managed = true
defer sub.abort()
err = fn(sub)
if err != nil {
return err
}
return sub.commit()
}
func (txn *Txn) bytes(val *C.MDB_val) []byte {
if txn.RawRead {
return getBytes(val)
}
return getBytesCopy(val)
}
// Get retrieves items from database dbi. If txn.RawRead is true the slice
// returned by Get references a readonly section of memory that must not be
// accessed after txn has terminated.
//
// See mdb_get.
func (txn *Txn) Get(dbi DBI, key []byte) ([]byte, error) {
kdata, kn := valBytes(key)
ret := C.lmdbgo_mdb_get(
txn._txn, C.MDB_dbi(dbi),
(*C.char)(unsafe.Pointer(&kdata[0])), C.size_t(kn),
txn.val,
)
err := operrno("mdb_get", ret)
if err != nil {
*txn.val = C.MDB_val{}
return nil, err
}
b := txn.bytes(txn.val)
*txn.val = C.MDB_val{}
return b, nil
}
func (txn *Txn) putNilKey(dbi DBI, flags uint) error {
// mdb_put with an empty key will always fail
ret := C.lmdbgo_mdb_put2(txn._txn, C.MDB_dbi(dbi), nil, 0, nil, 0, C.uint(flags))
return operrno("mdb_put", ret)
}
// Put stores an item in database dbi.
//
// See mdb_put.
func (txn *Txn) Put(dbi DBI, key []byte, val []byte, flags uint) error {
kn := len(key)
if kn == 0 {
return txn.putNilKey(dbi, flags)
}
vn := len(val)
if vn == 0 {
val = []byte{0}
}
ret := C.lmdbgo_mdb_put2(
txn._txn, C.MDB_dbi(dbi),
(*C.char)(unsafe.Pointer(&key[0])), C.size_t(kn),
(*C.char)(unsafe.Pointer(&val[0])), C.size_t(vn),
C.uint(flags),
)
return operrno("mdb_put", ret)
}
// PutReserve returns a []byte of length n that can be written to, potentially
// avoiding a memcopy. The returned byte slice is only valid in txn's thread,
// before it has terminated.
func (txn *Txn) PutReserve(dbi DBI, key []byte, n int, flags uint) ([]byte, error) {
if len(key) == 0 {
return nil, txn.putNilKey(dbi, flags)
}
txn.val.mv_size = C.size_t(n)
ret := C.lmdbgo_mdb_put1(
txn._txn, C.MDB_dbi(dbi),
(*C.char)(unsafe.Pointer(&key[0])), C.size_t(len(key)),
txn.val,
C.uint(flags|C.MDB_RESERVE),
)
err := operrno("mdb_put", ret)
if err != nil {
*txn.val = C.MDB_val{}
return nil, err
}
b := getBytes(txn.val)
*txn.val = C.MDB_val{}
return b, nil
}
// Del deletes an item from database dbi. Del ignores val unless dbi has the
// DupSort flag.
//
// See mdb_del.
func (txn *Txn) Del(dbi DBI, key, val []byte) error {
kdata, kn := valBytes(key)
vdata, vn := valBytes(val)
ret := C.lmdbgo_mdb_del(
txn._txn, C.MDB_dbi(dbi),
(*C.char)(unsafe.Pointer(&kdata[0])), C.size_t(kn),
(*C.char)(unsafe.Pointer(&vdata[0])), C.size_t(vn),
)
return operrno("mdb_del", ret)
}
// OpenCursor allocates and initializes a Cursor to database dbi.
//
// See mdb_cursor_open.
func (txn *Txn) OpenCursor(dbi DBI) (*Cursor, error) {
cur, err := openCursor(txn, dbi)
if cur != nil && txn.readonly {
runtime.SetFinalizer(cur, (*Cursor).close)
}
return cur, err
}
func (txn *Txn) errf(format string, v ...interface{}) {
if txn.errLogf != nil {
txn.errLogf(format, v...)
return
}
log.Printf(format, v...)
}
func (txn *Txn) finalize() {
if txn._txn != nil {
txn.errf("lmdb: aborting unreachable transaction %#x", uintptr(unsafe.Pointer(txn)))
txn.Abort()
}
}
// TxnOp is an operation applied to a managed transaction. The Txn passed to a
// TxnOp is managed and the operation must not call Commit, Abort, Renew, or
// Reset on it.
//
// IMPORTANT:
// TxnOps that write to the database (those passed to Env.Update or Txn.Sub)
// must not use the Txn in another goroutine (passing it directly or otherwise
// through closure). Doing so has undefined results.
type TxnOp func(txn *Txn) error