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/*-
* 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 WT_TXNID_LE(t1, t2) \
((t1) <= (t2))
#define WT_TXNID_LT(t1, t2) \
((t1) != (t2) && WT_TXNID_LE(t1, t2))
#define WT_SESSION_TXN_STATE(s) (&S2C(s)->txn_global.states[(s)->id])
#define WT_SESSION_IS_CHECKPOINT(s) \
((s)->id != 0 && (s)->id == S2C(s)->txn_global.checkpoint_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 {
uint64_t alloc; /* Transaction ID to allocate. */
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
* snapshot 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 transactions.
*/
volatile uint32_t checkpoint_id; /* Checkpoint's session ID */
volatile uint64_t checkpoint_gen;
volatile uint64_t checkpoint_pinned;
WT_TXN_STATE *states; /* Per-session transaction states */
};
typedef enum __wt_txn_isolation {
WT_ISO_EVICTION, /* Internal: eviction context */
WT_ISO_READ_UNCOMMITTED,
WT_ISO_READ_COMMITTED,
WT_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;
bool full_ckpt;
uint32_t ckpt_nsnapshot;
WT_ITEM *ckpt_snapshot;
#define WT_TXN_AUTOCOMMIT 0x01
#define WT_TXN_ERROR 0x02
#define WT_TXN_HAS_ID 0x04
#define WT_TXN_HAS_SNAPSHOT 0x08
#define WT_TXN_RUNNING 0x10
uint32_t flags;
};
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