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
|
/*-
* Copyright (c) 2014-2015 MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
#define WT_TXN_NONE 0 /* No txn running in a session. */
#define WT_TXN_FIRST 1 /* First transaction to run. */
#define WT_TXN_ABORTED UINT64_MAX /* Update rolled back, ignore. */
/*
* Transaction ID comparison dealing with edge cases.
*
* WT_TXN_ABORTED is the largest possible ID (never visible to a running
* transaction), WT_TXN_NONE is smaller than any possible ID (visible to all
* running transactions).
*/
#define TXNID_LE(t1, t2) \
((t1) <= (t2))
#define TXNID_LT(t1, t2) \
((t1) != (t2) && TXNID_LE(t1, t2))
#define WT_SESSION_TXN_STATE(s) (&S2C(s)->txn_global.states[(s)->id])
struct WT_COMPILER_TYPE_ALIGN(WT_CACHE_LINE_ALIGNMENT) __wt_txn_state {
volatile uint64_t id;
volatile uint64_t snap_min;
};
struct __wt_txn_global {
volatile uint64_t current; /* Current transaction ID. */
/* The oldest running transaction ID (may race). */
uint64_t last_running;
/*
* The oldest transaction ID that is not yet visible to some
* transaction in the system.
*/
volatile uint64_t oldest_id;
/* Count of scanning threads, or -1 for exclusive access. */
volatile int32_t scan_count;
/*
* Track information about the running checkpoint. The transaction IDs
* used when checkpointing are special. Checkpoints can run for a long
* time so we keep them out of regular visibility checks. Eviction and
* checkpoint operations know when they need to be aware of
* checkpoint IDs.
*/
volatile uint64_t checkpoint_gen;
volatile uint64_t checkpoint_id;
volatile uint64_t checkpoint_snap_min;
WT_TXN_STATE *states; /* Per-session transaction states */
};
typedef enum __wt_txn_isolation {
TXN_ISO_EVICTION, /* Internal: eviction context */
TXN_ISO_READ_UNCOMMITTED,
TXN_ISO_READ_COMMITTED,
TXN_ISO_SNAPSHOT
} WT_TXN_ISOLATION;
/*
* WT_TXN_OP --
* A transactional operation. Each transaction builds an in-memory array
* of these operations as it runs, then uses the array to either write log
* records during commit or undo the operations during rollback.
*/
struct __wt_txn_op {
uint32_t fileid;
enum {
TXN_OP_BASIC,
TXN_OP_INMEM,
TXN_OP_REF,
TXN_OP_TRUNCATE_COL,
TXN_OP_TRUNCATE_ROW
} type;
union {
/* TXN_OP_BASIC, TXN_OP_INMEM */
WT_UPDATE *upd;
/* TXN_OP_REF */
WT_REF *ref;
/* TXN_OP_TRUNCATE_COL */
struct {
uint64_t start, stop;
} truncate_col;
/* TXN_OP_TRUNCATE_ROW */
struct {
WT_ITEM start, stop;
enum {
TXN_TRUNC_ALL,
TXN_TRUNC_BOTH,
TXN_TRUNC_START,
TXN_TRUNC_STOP
} mode;
} truncate_row;
} u;
};
/*
* WT_TXN --
* Per-session transaction context.
*/
struct __wt_txn {
uint64_t id;
WT_TXN_ISOLATION isolation;
/*
* Snapshot data:
* ids < snap_min are visible,
* ids > snap_max are invisible,
* everything else is visible unless it is in the snapshot.
*/
uint64_t snap_min, snap_max;
uint64_t *snapshot;
uint32_t snapshot_count;
uint32_t txn_logsync; /* Log sync configuration */
/* Array of modifications by this transaction. */
WT_TXN_OP *mod;
size_t mod_alloc;
u_int mod_count;
/* Scratch buffer for in-memory log records. */
WT_ITEM *logrec;
/* Requested notification when transactions are resolved. */
WT_TXN_NOTIFY *notify;
/* Checkpoint status. */
WT_LSN ckpt_lsn;
int full_ckpt;
uint32_t ckpt_nsnapshot;
WT_ITEM *ckpt_snapshot;
#define TXN_AUTOCOMMIT 0x01
#define TXN_ERROR 0x02
#define TXN_HAS_ID 0x04
#define TXN_HAS_SNAPSHOT 0x08
#define TXN_RUNNING 0x10
uint32_t flags;
};
|
