From 46e5a515f4a07157e0733f70d3ab751cf0172214 Mon Sep 17 00:00:00 2001
From: Vladimir Davydov <vdavydov@tarantool.org>
Date: Tue, 11 Oct 2022 15:54:10 +0300
Subject: [PATCH] vinyl: maintain list of all prepared transactions
This commit replaces vy_tx_manager::last_prepared_tx with a list of all
prepared transactions sorted by PSN. We need this list to find the
newest prepared transaction that is older than a given PSN, which is
required to switch to the most recent read view in the 'best-effort'
isolation level when an unconfirmed (prepared) statement is skipped.
Needed for #5522
NO_DOC=internal
NO_TEST=internal
NO_CHANGELOG=internal
---
src/box/vy_tx.c | 48 ++++++++++++++++++++++--------------------------
src/box/vy_tx.h | 12 +++++++-----
2 files changed, 29 insertions(+), 31 deletions(-)
diff --git a/src/box/vy_tx.c b/src/box/vy_tx.c
index a64190e678..10fb115993 100644
--- a/src/box/vy_tx.c
+++ b/src/box/vy_tx.c
@@ -109,6 +109,7 @@ vy_tx_manager_new(void)
}
rlist_create(&xm->writers);
+ rlist_create(&xm->prepared);
rlist_create(&xm->read_views);
vy_global_read_view_create((struct vy_read_view *)&xm->global_read_view,
INT64_MAX);
@@ -164,13 +165,15 @@ vy_tx_manager_read_view(struct vy_tx_manager *xm)
* Check if the last read view can be reused. Reference
* and return it if it's the case.
*/
+ struct vy_tx *last_prepared_tx = rlist_empty(&xm->prepared) ? NULL :
+ rlist_last_entry(&xm->prepared, struct vy_tx, in_prepared);
if (!rlist_empty(&xm->read_views)) {
rv = rlist_last_entry(&xm->read_views, struct vy_read_view,
in_read_views);
/** Reuse an existing read view */
- if ((xm->last_prepared_tx == NULL && rv->vlsn == xm->lsn) ||
- (xm->last_prepared_tx != NULL &&
- rv->vlsn == MAX_LSN + xm->last_prepared_tx->psn)) {
+ if ((last_prepared_tx == NULL && rv->vlsn == xm->lsn) ||
+ (last_prepared_tx != NULL &&
+ rv->vlsn == MAX_LSN + last_prepared_tx->psn)) {
rv->refs++;
return rv;
@@ -182,9 +185,9 @@ vy_tx_manager_read_view(struct vy_tx_manager *xm)
"mempool", "read view");
return NULL;
}
- if (xm->last_prepared_tx != NULL) {
- rv->vlsn = MAX_LSN + xm->last_prepared_tx->psn;
- xm->last_prepared_tx->read_view = rv;
+ if (last_prepared_tx != NULL) {
+ rv->vlsn = MAX_LSN + last_prepared_tx->psn;
+ last_prepared_tx->read_view = rv;
rv->refs = 2;
} else {
rv->vlsn = xm->lsn;
@@ -332,11 +335,14 @@ vy_tx_create(struct vy_tx_manager *xm, struct vy_tx *tx)
tx->psn = 0;
rlist_create(&tx->on_destroy);
rlist_create(&tx->in_writers);
+ rlist_create(&tx->in_prepared);
}
void
vy_tx_destroy(struct vy_tx *tx)
{
+ assert(rlist_empty(&tx->in_prepared));
+
trigger_run(&tx->on_destroy, NULL);
trigger_destroy(&tx->on_destroy);
@@ -765,7 +771,8 @@ vy_tx_prepare(struct vy_tx *tx)
return -1;
v->region_stmt = *region_stmt;
}
- xm->last_prepared_tx = tx;
+ assert(rlist_empty(&tx->in_prepared));
+ rlist_add_tail_entry(&xm->prepared, tx, in_prepared);
return 0;
}
@@ -777,12 +784,12 @@ vy_tx_commit(struct vy_tx *tx, int64_t lsn)
xm->stat.commit++;
- if (xm->last_prepared_tx == tx)
- xm->last_prepared_tx = NULL;
-
if (vy_tx_is_ro(tx))
goto out;
+ assert(!rlist_empty(&tx->in_prepared));
+ rlist_del_entry(tx, in_prepared);
+
assert(xm->lsn <= lsn);
xm->lsn = lsn;
@@ -813,28 +820,17 @@ vy_tx_rollback_after_prepare(struct vy_tx *tx)
{
assert(tx->state == VINYL_TX_COMMIT);
- struct vy_tx_manager *xm = tx->xm;
-
/*
* There are two reasons of rollback_after_prepare:
* 1) Fail in the middle of vy_tx_prepare call.
* 2) Cascading rollback after WAL fail.
*
- * If a TX is the latest prepared TX and the it is rollbacked,
- * it's certainly the case (2) and we should set xm->last_prepared_tx
- * to the previous prepared TX, if any.
- * But doesn't know the previous TX.
- * On the other hand we may expect that cascading rollback will
- * concern all the prepared TXs, all of them will be rollbacked
- * and xm->last_prepared_tx must be set to NULL in the end.
- * Thus we can set xm->last_prepared_tx to NULL now and it will be
- * correct in the end of the cascading rollback.
- *
- * We must not change xm->last_prepared_tx in all other cases,
- * it will be changed by the corresponding TX.
+ * In the first case, the transaction isn't in the list of prepared
+ * transactions hence there's no assertion that the tx->in_prepared
+ * link must not be an empty list head (rlist_del is a no-op if the
+ * link is an empty head).
*/
- if (xm->last_prepared_tx == tx)
- xm->last_prepared_tx = NULL;
+ rlist_del_entry(tx, in_prepared);
struct txv *v;
stailq_foreach_entry(v, &tx->log, next_in_log) {
diff --git a/src/box/vy_tx.h b/src/box/vy_tx.h
index 4fac5f6e2a..e44bc9cbf6 100644
--- a/src/box/vy_tx.h
+++ b/src/box/vy_tx.h
@@ -142,6 +142,8 @@ write_set_search_key(write_set_t *tree, struct vy_lsm *lsm,
struct vy_tx {
/** Link in vy_tx_manager::writers. */
struct rlist in_writers;
+ /** Link in vy_tx_manager::prepared. */
+ struct rlist in_prepared;
/** Transaction manager. */
struct vy_tx_manager *xm;
/**
@@ -222,15 +224,15 @@ struct vy_tx_manager {
* transactions in vy_mem.
*/
int64_t psn;
- /**
- * The last prepared (but not committed) transaction,
- * or NULL if there are no prepared transactions.
- */
- struct vy_tx *last_prepared_tx;
/**
* List of rw transactions, linked by vy_tx::in_writers.
*/
struct rlist writers;
+ /**
+ * List of prepared (but not committed) transaction,
+ * sorted by PSN ascending, linked by vy_tx::in_prepared.
+ */
+ struct rlist prepared;
/**
* The list of TXs with a read view in order of vlsn.
*/
--
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