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Binlog-in-engine: Implement savepoint support

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Support for SAVEPOINT, ROLLBACK TO SAVEPOINT, rolling back a failed
statement (keeping active transaction), and rolling back transaction.

For savepoints (and start-of-statement), if the binlog data to be rolled
back is still in the in-memory part of trx cache we can just truncate the
cache to the point.

But if we need to spill cache contents as out-of-band data containing one or
more savepoints/start-of-statement point, then split the spill at each point
and inform the engine of the savepoints.

In InnoDB, at savepoint set, save the state of the forest of perfect binary
trees being built. Then at rollback, restore the appropriate state.

Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
This commit is contained in:
Kristian Nielsen
2025-07-15 13:16:33 +02:00
parent 95ea6e15a6
commit 31ba7922a0
9 changed files with 981 additions and 32 deletions
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23
sql/handler.h
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@@ -1566,11 +1566,32 @@ struct handlerton
must be binlogged transactionally during COMMIT. The engine_data points to
a pointer location that the engine can set to maintain its own context
for the out-of-band data.
Optionally savepoints can be set at the point at the start of the write
(ie. before any written data), when stmt_start_data and/or savepoint_data
are non-NULL. Such a point can later be rolled back to by calling
binlog_savepoint_rollback(). (Only) if stmt_start_data or savepoint_data
is non-null can data_len be null (to set savepoint(s) and do nothing else).
*/
bool (*binlog_oob_data_ordered)(THD *thd, const unsigned char *data,
size_t data_len, void **engine_data);
size_t data_len, void **engine_data,
void **stmt_start_data,
void **savepoint_data);
bool (*binlog_oob_data)(THD *thd, const unsigned char *data,
size_t data_len, void **engine_data);
/*
Rollback to a prior point in out-of-band binlogged partial transaction
data, for savepoint support. The stmt_start_data and/or savepoint_data,
if non-NULL, correspond to the point set by an earlier binlog_oob_data()
call.
Exactly one of stmt_start_data or savepoint_data will be non-NULL,
corresponding to either rolling back to the start of the current statement,
or to an earlier set savepoint.
*/
void (*binlog_savepoint_rollback)(THD *thd, void **engine_data,
void **stmt_start_data,
void **savepoint_data);
/*
Call to reset (for new transactions) the engine_data from
binlog_oob_data(). Can also change the pointer to point to different data