/**********************************************************************//**
If required, flushes the log to disk if we called trx_commit_for_mysql()
with trx->flush_log_later == TRUE.
@return 0 or error number */
UNIV_INTERN
ulint
trx_commit_complete_for_mysql(
/*==========================*/
trx_t* trx) /*!< in: trx handle */
{
ib_uint64_t lsn = trx->commit_lsn;
ut_a(trx);
trx->op_info = "flushing log";
if (!trx->must_flush_log_later) {
/* Do nothing */
} else if (srv_flush_log_at_trx_commit == 0) {
/* Do nothing */
} else if (srv_flush_log_at_trx_commit == 1) {
if (srv_unix_file_flush_method == SRV_UNIX_NOSYNC) {
/* Write the log but do not flush it to disk */
log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, FALSE);
} else {
/* Write the log to the log files AND flush them to
disk */
log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, TRUE);
}
} else if (srv_flush_log_at_trx_commit == 2) {
/* Write the log but do not flush it to disk */
log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, FALSE);
} else {
ut_error;
}
trx->must_flush_log_later = FALSE;
trx->op_info = "";
return(0);
}
/************************************************************************
Does an asynchronous write of a buffer page. NOTE: in simulated aio and
also when the doublewrite buffer is used, we must call
buf_flush_buffered_writes after we have posted a batch of writes! */
static
void
buf_flush_write_block_low(
/*======================*/
buf_block_t* block) /* in: buffer block to write */
{
#ifdef UNIV_LOG_DEBUG
static ibool univ_log_debug_warned;
#endif /* UNIV_LOG_DEBUG */
ut_a(block->state == BUF_BLOCK_FILE_PAGE);
#ifdef UNIV_IBUF_DEBUG
ut_a(ibuf_count_get(block->space, block->offset) == 0);
#endif
ut_ad(!ut_dulint_is_zero(block->newest_modification));
#ifdef UNIV_LOG_DEBUG
if (!univ_log_debug_warned) {
univ_log_debug_warned = TRUE;
fputs("Warning: cannot force log to disk if"
" UNIV_LOG_DEBUG is defined!\n"
"Crash recovery will not work!\n",
stderr);
}
#else
/* Force the log to the disk before writing the modified block */
log_write_up_to(block->newest_modification, LOG_WAIT_ALL_GROUPS, TRUE);
#endif
buf_flush_init_for_writing(block->frame, block->newest_modification,
block->space, block->offset);
if (!srv_use_doublewrite_buf || !trx_doublewrite) {
fil_io(OS_FILE_WRITE | OS_AIO_SIMULATED_WAKE_LATER,
FALSE, block->space, block->offset, 0, UNIV_PAGE_SIZE,
(void*)block->frame, (void*)block);
} else {
buf_flush_post_to_doublewrite_buf(block);
}
}
/****************************************************************//**
Commits a transaction. */
UNIV_INTERN
void
trx_commit_off_kernel(
/*==================*/
trx_t* trx) /*!< in: transaction */
{
page_t* update_hdr_page;
ib_uint64_t lsn = 0;
trx_rseg_t* rseg;
trx_undo_t* undo;
mtr_t mtr;
ut_ad(mutex_own(&kernel_mutex));
trx->must_flush_log_later = FALSE;
rseg = trx->rseg;
if (trx->insert_undo != NULL || trx->update_undo != NULL) {
mutex_exit(&kernel_mutex);
mtr_start(&mtr);
/* Change the undo log segment states from TRX_UNDO_ACTIVE
to some other state: these modifications to the file data
structure define the transaction as committed in the file
based world, at the serialization point of the log sequence
number lsn obtained below. */
mutex_enter(&(rseg->mutex));
if (trx->insert_undo != NULL) {
trx_undo_set_state_at_finish(
rseg, trx, trx->insert_undo, &mtr);
}
undo = trx->update_undo;
if (undo) {
mutex_enter(&kernel_mutex);
trx->no = trx_sys_get_new_trx_no();
mutex_exit(&kernel_mutex);
/* It is not necessary to obtain trx->undo_mutex here
because only a single OS thread is allowed to do the
transaction commit for this transaction. */
update_hdr_page = trx_undo_set_state_at_finish(
rseg, trx, undo, &mtr);
/* We have to do the cleanup for the update log while
holding the rseg mutex because update log headers
have to be put to the history list in the order of
the trx number. */
trx_undo_update_cleanup(trx, update_hdr_page, &mtr);
}
mutex_exit(&(rseg->mutex));
/* Update the latest MySQL binlog name and offset info
in trx sys header if MySQL binlogging is on or the database
server is a MySQL replication slave */
if (trx->mysql_log_file_name
&& trx->mysql_log_file_name[0] != '\0') {
trx_sys_update_mysql_binlog_offset(
trx->mysql_log_file_name,
trx->mysql_log_offset,
TRX_SYS_MYSQL_LOG_INFO, &mtr);
trx->mysql_log_file_name = NULL;
}
/* The following call commits the mini-transaction, making the
whole transaction committed in the file-based world, at this
log sequence number. The transaction becomes 'durable' when
we write the log to disk, but in the logical sense the commit
in the file-based data structures (undo logs etc.) happens
here.
NOTE that transaction numbers, which are assigned only to
transactions with an update undo log, do not necessarily come
in exactly the same order as commit lsn's, if the transactions
have different rollback segments. To get exactly the same
order we should hold the kernel mutex up to this point,
adding to the contention of the kernel mutex. However, if
a transaction T2 is able to see modifications made by
a transaction T1, T2 will always get a bigger transaction
number and a bigger commit lsn than T1. */
/*--------------*/
mtr_commit(&mtr);
/*--------------*/
lsn = mtr.end_lsn;
mutex_enter(&kernel_mutex);
}
ut_ad(trx->conc_state == TRX_ACTIVE
|| trx->conc_state == TRX_PREPARED);
ut_ad(mutex_own(&kernel_mutex));
/* The following assignment makes the transaction committed in memory
and makes its changes to data visible to other transactions.
NOTE that there is a small discrepancy from the strict formal
visibility rules here: a human user of the database can see
modifications made by another transaction T even before the necessary
log segment has been flushed to the disk. If the database happens to
crash before the flush, the user has seen modifications from T which
will never be a committed transaction. However, any transaction T2
which sees the modifications of the committing transaction T, and
which also itself makes modifications to the database, will get an lsn
larger than the committing transaction T. In the case where the log
flush fails, and T never gets committed, also T2 will never get
committed. */
/*--------------------------------------*/
trx->conc_state = TRX_COMMITTED_IN_MEMORY;
/*--------------------------------------*/
/* If we release kernel_mutex below and we are still doing
recovery i.e.: back ground rollback thread is still active
then there is a chance that the rollback thread may see
this trx as COMMITTED_IN_MEMORY and goes adhead to clean it
up calling trx_cleanup_at_db_startup(). This can happen
in the case we are committing a trx here that is left in
PREPARED state during the crash. Note that commit of the
rollback of a PREPARED trx happens in the recovery thread
while the rollback of other transactions happen in the
background thread. To avoid this race we unconditionally
unset the is_recovered flag from the trx. */
trx->is_recovered = FALSE;
lock_release_off_kernel(trx);
if (trx->global_read_view) {
read_view_close(trx->global_read_view);
mem_heap_empty(trx->global_read_view_heap);
trx->global_read_view = NULL;
}
trx->read_view = NULL;
if (lsn) {
mutex_exit(&kernel_mutex);
if (trx->insert_undo != NULL) {
trx_undo_insert_cleanup(trx);
}
/* NOTE that we could possibly make a group commit more
efficient here: call os_thread_yield here to allow also other
trxs to come to commit! */
/*-------------------------------------*/
/* Depending on the my.cnf options, we may now write the log
buffer to the log files, making the transaction durable if
the OS does not crash. We may also flush the log files to
disk, making the transaction durable also at an OS crash or a
power outage.
The idea in InnoDB's group commit is that a group of
transactions gather behind a trx doing a physical disk write
to log files, and when that physical write has been completed,
one of those transactions does a write which commits the whole
group. Note that this group commit will only bring benefit if
there are > 2 users in the database. Then at least 2 users can
gather behind one doing the physical log write to disk.
If we are calling trx_commit() under prepare_commit_mutex, we
will delay possible log write and flush to a separate function
trx_commit_complete_for_mysql(), which is only called when the
thread has released the mutex. This is to make the
group commit algorithm to work. Otherwise, the prepare_commit
mutex would serialize all commits and prevent a group of
transactions from gathering. */
if (trx->flush_log_later) {
/* Do nothing yet */
trx->must_flush_log_later = TRUE;
} else if (srv_flush_log_at_trx_commit == 0) {
/* Do nothing */
} else if (srv_flush_log_at_trx_commit == 1) {
if (srv_unix_file_flush_method == SRV_UNIX_NOSYNC) {
/* Write the log but do not flush it to disk */
log_write_up_to(lsn, LOG_WAIT_ONE_GROUP,
FALSE);
} else {
/* Write the log to the log files AND flush
them to disk */
log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, TRUE);
}
} else if (srv_flush_log_at_trx_commit == 2) {
/* Write the log but do not flush it to disk */
log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, FALSE);
} else {
ut_error;
}
trx->commit_lsn = lsn;
/*-------------------------------------*/
mutex_enter(&kernel_mutex);
}
/* Free all savepoints */
trx_roll_free_all_savepoints(trx);
trx->conc_state = TRX_NOT_STARTED;
trx->rseg = NULL;
trx->undo_no = ut_dulint_zero;
trx->last_sql_stat_start.least_undo_no = ut_dulint_zero;
ut_ad(UT_LIST_GET_LEN(trx->wait_thrs) == 0);
ut_ad(UT_LIST_GET_LEN(trx->trx_locks) == 0);
UT_LIST_REMOVE(trx_list, trx_sys->trx_list, trx);
}
/****************************************************************//**
Prepares a transaction. */
UNIV_INTERN
void
trx_prepare_off_kernel(
/*===================*/
trx_t* trx) /*!< in: transaction */
{
trx_rseg_t* rseg;
ib_uint64_t lsn = 0;
mtr_t mtr;
ut_ad(mutex_own(&kernel_mutex));
rseg = trx->rseg;
if (trx->insert_undo != NULL || trx->update_undo != NULL) {
mutex_exit(&kernel_mutex);
mtr_start(&mtr);
/* Change the undo log segment states from TRX_UNDO_ACTIVE
to TRX_UNDO_PREPARED: these modifications to the file data
structure define the transaction as prepared in the
file-based world, at the serialization point of lsn. */
mutex_enter(&(rseg->mutex));
if (trx->insert_undo != NULL) {
/* It is not necessary to obtain trx->undo_mutex here
because only a single OS thread is allowed to do the
transaction prepare for this transaction. */
trx_undo_set_state_at_prepare(trx, trx->insert_undo,
&mtr);
}
if (trx->update_undo) {
trx_undo_set_state_at_prepare(
trx, trx->update_undo, &mtr);
}
mutex_exit(&(rseg->mutex));
/*--------------*/
mtr_commit(&mtr); /* This mtr commit makes the
transaction prepared in the file-based
world */
/*--------------*/
lsn = mtr.end_lsn;
mutex_enter(&kernel_mutex);
}
ut_ad(mutex_own(&kernel_mutex));
/*--------------------------------------*/
trx->conc_state = TRX_PREPARED;
/*--------------------------------------*/
if (lsn) {
/* Depending on the my.cnf options, we may now write the log
buffer to the log files, making the prepared state of the
transaction durable if the OS does not crash. We may also
flush the log files to disk, making the prepared state of the
transaction durable also at an OS crash or a power outage.
The idea in InnoDB's group prepare is that a group of
transactions gather behind a trx doing a physical disk write
to log files, and when that physical write has been completed,
one of those transactions does a write which prepares the whole
group. Note that this group prepare will only bring benefit if
there are > 2 users in the database. Then at least 2 users can
gather behind one doing the physical log write to disk.
TODO: find out if MySQL holds some mutex when calling this.
That would spoil our group prepare algorithm. */
mutex_exit(&kernel_mutex);
if (srv_flush_log_at_trx_commit == 0) {
/* Do nothing */
} else if (srv_flush_log_at_trx_commit == 1) {
if (srv_unix_file_flush_method == SRV_UNIX_NOSYNC) {
/* Write the log but do not flush it to disk */
log_write_up_to(lsn, LOG_WAIT_ONE_GROUP,
FALSE);
} else {
/* Write the log to the log files AND flush
them to disk */
log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, TRUE);
}
} else if (srv_flush_log_at_trx_commit == 2) {
/* Write the log but do not flush it to disk */
log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, FALSE);
} else {
ut_error;
}
mutex_enter(&kernel_mutex);
}
}
