[Tarantool-patches] [PATCH v4 02/12] txm: add TX status

[Aleksandr Lyapunov <alyapunov@tarantool.org>]

Transaction engine (see further commits) needs to distinguish and
maniputate transactions by their status. The status describe the
lifetime point of a transaction (inprogress, prepared, committed)
and its abilities (conflicted, read view).

Part of #4897
Part of #5108
---
 src/box/txn.c |  5 +++++
 src/box/txn.h | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/src/box/txn.c b/src/box/txn.c
index b2d3423..093808a 100644
--- a/src/box/txn.c
+++ b/src/box/txn.c
@@ -224,6 +224,7 @@ txn_begin(void)
 	txn->flags = 0;
 	txn->in_sub_stmt = 0;
 	txn->id = ++tsn;
+	txn->status = TXN_INPROGRESS;
 	txn->signature = TXN_SIGNATURE_ROLLBACK;
 	txn->engine = NULL;
 	txn->engine_tx = NULL;
@@ -449,6 +450,7 @@ txn_complete(struct txn *txn)
 	 * IPROTO_NOP or IPROTO_CONFIRM statements.
 	 */
 	if (txn->signature < 0) {
+		txn->status = TXN_ABORTED;
 		/* Undo the transaction. */
 		struct txn_stmt *stmt;
 		stailq_reverse(&txn->stmts);
@@ -459,6 +461,7 @@ txn_complete(struct txn *txn)
 		if (txn_has_flag(txn, TXN_HAS_TRIGGERS))
 			txn_run_rollback_triggers(txn, &txn->on_rollback);
 	} else if (!txn_has_flag(txn, TXN_WAIT_SYNC)) {
+		txn->status = TXN_COMMITTED;
 		/* Commit the transaction. */
 		if (txn->engine != NULL)
 			engine_commit(txn->engine, txn);
@@ -656,6 +659,7 @@ txn_prepare(struct txn *txn)
 		trigger_clear(&txn->fiber_on_yield);
 
 	txn->start_tm = ev_monotonic_now(loop());
+	txn->status = TXN_PREPARED;
 	return 0;
 }
 
@@ -872,6 +876,7 @@ void
 txn_rollback(struct txn *txn)
 {
 	assert(txn == in_txn());
+	txn->status = TXN_ABORTED;
 	trigger_clear(&txn->fiber_on_stop);
 	if (!txn_has_flag(txn, TXN_CAN_YIELD))
 		trigger_clear(&txn->fiber_on_yield);
diff --git a/src/box/txn.h b/src/box/txn.h
index 36b1a03..35e1ab9 100644
--- a/src/box/txn.h
+++ b/src/box/txn.h
@@ -121,6 +121,40 @@ enum {
 };
 
 /**
+ * Status of a transaction.
+ */
+enum txn_status {
+	/**
+	 * Initial state of TX. The only state of a TX that allowed to do
+	 * read or write actions.
+	 */
+	TXN_INPROGRESS,
+	/**
+	 * The TX have passed conflict checks and is ready to be committed.
+	 */
+	TXN_PREPARED,
+	/**
+	 * The TX was aborted when other TX was committed due to conflict.
+	 */
+	TXN_CONFLICTED,
+	/**
+	 * The TX was read_only, has a conflict and was sent to read view.
+	 * Read-only and does not participate in conflict resolution ever more.
+	 * This transaction can only see a state of the database at some fixed
+	 * point in the past.
+	 */
+	TXN_IN_READ_VIEW,
+	/**
+	 * The TX was committed.
+	 */
+	TXN_COMMITTED,
+	/**
+	 * The TX was aborted.
+	 */
+	TXN_ABORTED,
+};
+
+/**
  * A single statement of a multi-statement
  * transaction: undo and redo info.
  */
@@ -217,6 +251,8 @@ struct txn {
 	 * Valid IDs start from 1.
 	 */
 	int64_t id;
+	/** Status of the TX */
+	enum txn_status status;
 	/** List of statements in a transaction. */
 	struct stailq stmts;
 	/** Number of new rows without an assigned LSN. */
-- 
2.7.4