specific temporary errors
The optimistic parallel slave's worker thread could face a run-time error due to
the algorithm's specifics which allows for conflicts like the reported
"Can't find record in 'table'".
A typical stack is like
{noformat}
#0 handler::print_error (this=0x61c00008f8a0, error=149, errflag=0) at handler.cc:3650
#1 0x0000555555e95361 in write_record (thd=thd@entry=0x62a0000a2208, table=table@entry=0x61f00008ce88, info=info@entry=0x7fffdee356d0) at sql_insert.cc:1944
#2 0x0000555555ea7767 in mysql_insert (thd=thd@entry=0x62a0000a2208, table_list=0x61b00012ada0, fields=..., values_list=..., update_fields=..., update_values=..., duplic=<optimized out>, ignore=<optimized out>) at sql_insert.cc:1039
#3 0x0000555555efda90 in mysql_execute_command (thd=thd@entry=0x62a0000a2208) at sql_parse.cc:3927
#4 0x0000555555f0cc50 in mysql_parse (thd=0x62a0000a2208, rawbuf=<optimized out>, length=<optimized out>, parser_state=<optimized out>) at sql_parse.cc:7449
#5 0x00005555566d4444 in Query_log_event::do_apply_event (this=0x61200005b9c8, rgi=<optimized out>, query_arg=<optimized out>, q_len_arg=<optimized out>) at log_event.cc:4508
#6 0x00005555566d639e in Query_log_event::do_apply_event (this=<optimized out>, rgi=<optimized out>) at log_event.cc:4185
#7 0x0000555555d738cf in Log_event::apply_event (rgi=0x61d0001ea080, this=0x61200005b9c8) at log_event.h:1343
#8 apply_event_and_update_pos_apply (ev=ev@entry=0x61200005b9c8, thd=thd@entry=0x62a0000a2208, rgi=rgi@entry=0x61d0001ea080, reason=<optimized out>) at slave.cc:3479
#9 0x0000555555d8596b in apply_event_and_update_pos_for_parallel (ev=ev@entry=0x61200005b9c8, thd=thd@entry=0x62a0000a2208, rgi=rgi@entry=0x61d0001ea080) at slave.cc:3623
#10 0x00005555562aca83 in rpt_handle_event (qev=qev@entry=0x6190000fa088, rpt=rpt@entry=0x62200002bd68) at rpl_parallel.cc:50
#11 0x00005555562bd04e in handle_rpl_parallel_thread (arg=arg@entry=0x62200002bd68) at rpl_parallel.cc:1258
{noformat}
Here {{handler::print_error}} computes whether to error log the
current error when --log-warnings > 1. The decision flag is consulted
bu {{my_message_sql()}} which can be eventually called.
In the bug case the decision is to log.
However in the optimistic mode slave applier case any conflict is
attempted to resolve with rollback and retry to success. Hence the
logging is at least extraneous.
The case is fixed with adding a new flag {{ME_LOG_AS_WARN}} which
{{handler::print_error}} may propagate further on through {{my_error}}
when the error comes from an optimistically running slave worker thread.
The new flag effectively requests the warning level for the errlog record,
while the thread's DA records the actual error (which is regarded as temporary one
by the parallel slave error handler).
Do not try to set versioning conditions on every SP call. It may work
incorrectly, but it's a general bug described in MDEV-774.
This patch makes system versioning stuff consistent with other code and
also fixes a use-after-free bug.
Closes#756
Fixed by deleting the sequence if we where not able to initialize it
I also noticed that we didn't always set the error message when
check_killed(), which could lead to aborted queries without error
beeing properly set. Fixed by default setting error message if
check_error() noticed that killed had been called.
This allowed me to remove a lot of calls to thd->send_kill_message().
Being executed under slow_log is ON the test revealed a "side-effect"
in MDEV-8305 implementation which inadvertently made the trigger or
stored function statements to reset the top-level query's
THD::start_time et al. (Details of the test failure analysis are footnoted).
Unlike the SP case the SF and Trigger's internal statement should not
do that.
Fixed with revising the MDEV-8305 decision to backup/reset/restore
the session timestamp inside sp_instr_stmt::execute(). The timestamp
actually remains reset in the SP case by its caller per statement basis by ever
existing logics.
Timestamps related tests are extended to cover the trigger and stored function case.
Note, commit 3395ab7324 is reverted as its struct QUERY_START_TIME_INFO
declaration is not in use anymore after this patch.
Footnote:
--------
Specifically to the failing test, a query on the master was logged
okay with a timestamp of the query's top-level statement but its post
update trigger managed to compute one more (later) timestamp which got
inserted into another table. The latter table master-vs-slave
no fractional part timestamp discrepancy became evident
thanks to different execution time of the trigger combined with the
fact of the logged with micro-second fractional part master timestamp
was truncated on the slave. On master when the fractional part was
close to 1 the trigger execution added up its own latency to overflow
to next second value. That's how the master timestamp surprisingly
turned out to bigger than the slave's one.
preserve positions if the multi-update join is using tmp table:
* store positions in the tmp table if needed
JOIN::add_fields_for_current_rowid()
* take positions from the tmp table, not from file->position():
multi_update::prepare2()
Store transaction start time in thd->transaction.start_time.
THD::transaction_time() wraps over transaction.start_time taking into
account current status of BEGIN.
Don't use hidden system time in versioning,
but keep the system time logic in THD
to workaround low-res system clock and
replication not versioned to versioned.
This reverts MDEV-14788 (System versioning cannot
be based on local timestamps, as it is now).
Versioning is based on local timestamps again,
but timestamps are protected by MDEV-15923
(option to control who can set session @@timestamp).
1. Adding THD::convert_string(LEX_CSTRING *to,...) as a wrapper
for convert_string(LEX_STRING *to,...), as LEX_CSTRING
is now frequently used for conversion purpose.
This reduced duplicate code in TEXT_STRING_sys,
TEXT_STRING_literal, TEXT_STRING_filesystem grammar rules in *.yy
2. Adding yet another THD::convert_string() with an extra parameter
"bool simple_copy_is_possible". This even more reduced
repeatable code in the mentioned grammar rules in *.yy
3. Deriving Lex_ident_cli_st from Lex_string_with_metadata_st,
as they have very similar functionality. Moving m_quote
from Lex_ident_cli_st to Lex_string_with_metadata_st,
as m_quote will be used later to optimize string literals anyway
(e.g. avoid redundant copying on the tokenizer stage).
Adjusting Lex_input_stream::get_text() accordingly.
4. Moving the reminders of the code in TEXT_STRING_sys, TEXT_STRING_literal,
TEXT_STRING_filesystem grammar rules as new methods in THD:
- make_text_string_sys()
- make_text_string_connection()
- make_text_string_filesystem()
and changing *.yy to use these new methods.
This reduced the amount of similar code in
sql_yacc.yy and sql_yacc_ora.yy.
5. Removing duplicate code in Lex_input_stream::body_utf8_append_ident():
by reusing THD::make_text_string_sys(). Thanks to #3 and #4.
6. Making THD members charset_is_system_charset,
charset_is_collation_connection, charset_is_character_set_filesystem
private, as they are not needed externally any more.
The code in the "sp_tail" rule in sql_yacc.yy always
used YYLIP->get_cpp_tok_start() as the start of the body,
and did not check for possible lookahead which happens
for keywords "FOR", "VALUES" and "WITH" for LALR(2)
resolution in Lex_input_stream::lex_token().
In case of the lookahead token presence,
get_tok_start_prev() should have been used instead
of get_cpp_tok_start() as the beginning of the SP body.
Change summary:
This patch hides the implementation of the lookahead
token completely inside Lex_input_stream.
The users of Lex_input_stream now just get token-by-token
transparently and should not care about lookahead any more.
Now external users of Lex_input_stream
are not aware of the lookahead token at all.
Change details:
- Moving Lex_input_stream::has_lookahead() into the "private" section.
- Removing Lex_input_stream::get_tok_start_prev() and
Lex_input_stream::get_cpp_start_prev().
- Fixing the external code to call get_tok_start() and get_cpp_tok_start()
in all places where get_tok_start_prev() and get_cpp_start_prev()
where used.
- Adding a test for has_lookahead() right inside
get_tok_start() and get_cpp_tok_start().
If there is a lookahead token, these methods now
return the position of the previous token automatically:
const char *get_tok_start()
{
return has_lookahead() ? m_tok_start_prev : m_tok_start;
}
const char *get_cpp_tok_start()
{
return has_lookahead() ? m_cpp_tok_start_prev : m_cpp_tok_start;
}
- Fixing the internal code inside Lex_input_stream methods
to use m_tok_start and m_cpp_tok_start directly,
instead of calling get_tok_start() and get_cpp_tok_start(),
to make sure to access to the *current* token position
(independently of a lookahead token presence).
Reasoning:
- Shorter and clearer code
- Better encapsulation
(a fair number of Lex_input_stream methods and members were
moved to the private section)
New methods:
int lex_token(union YYSTYPE *yylval, THD *thd);
bool consume_comment(int remaining_recursions_permitted);
int lex_one_token(union YYSTYPE *yylval, THD *thd);
int find_keyword(Lex_ident_cli_st *str, uint len, bool function);
LEX_CSTRING get_token(uint skip, uint length);
Additional changes:
- Removing Lex_input_stream::yylval.
In the original code it was just an alias
for the "yylval" passed to lex_one_token().
This coding style is bug prone and is hard to follow.
In the new reduction "yylval" (or its components) is passed to
the affected methods as a parameter.
- Moving the code in sql_lex.h up and down between "private" and "public"
sections (sorry if this made the diff somewhat harder to read)
Introduced new alter algorithm type called NOCOPY & INSTANT for
inplace alter operation.
NOCOPY - Algorithm refuses any alter operation that would
rebuild the clustered index. It is a subset of INPLACE algorithm.
INSTANT - Algorithm allow any alter operation that would
modify only meta data. It is a subset of NOCOPY algorithm.
Introduce new variable called alter_algorithm. The values are
DEFAULT(0), COPY(1), INPLACE(2), NOCOPY(3), INSTANT(4)
Message to deprecate old_alter_table variable and make it alias
for alter_algorithm variable.
alter_algorithm variable for slave is always set to default.
The code passing positions in the query to constructors of
Rewritable_query_parameter descendants (e.g. Item_splocal)
was not reliable. It used various Lex_input_stream methods:
- get_tok_start()
- get_tok_start_prev()
- get_tok_end()
- get_ptr()
to find positions of the recently scanned tokens.
The challenge was mostly to choose between get_tok_start()
and get_tok_start_prev(), taking into account to the current
grammar (depending if lookahead takes place before
or after we read the positions in every particular rule).
But this approach did not work at all in combination
with token contractions, when MYSQLlex() translates
two tokens into one token ID, for example:
WITH ROLLUP -> WITH_ROLLUP_SYM
As a result, the tokenizer is already one more token ahead.
So in query fragment:
"GROUP BY d, spvar WITH ROLLUP"
get_tok_start() points to "ROLLUP".
get_tok_start_prev() points to "WITH".
As a result, it was "WITH" who was erroneously replaced
to NAME_CONST() instead of "spvar".
This patch modifies the code to do it a different way.
Changes:
1. For keywords and identifiers, the tokenizer now
returns LEX_CTRING pointing directly to the query
fragment. So query positions are now just available using:
- $1.str - for the beginning of a token
- $1.str+$1.length - for the end of a token
2. Identifiers are not allocated on the THD memory root
in the tokenizer any more. Allocation is now done
on later stages, in methods like LEX::create_item_ident().
3. Two LEX_CSTRING based structures were added:
- Lex_ident_cli_st - used to store the "client side"
identifier representation, pointing to the
query fragment. Note, these identifiers
are encoded in @@character_set_client
and can have broken byte sequences.
- Lex_ident_sys_st - used to store the "server side"
identifier representation, pointing to the
THD allocated memory. This representation
guarantees that the identifier was checked
for being well-formed, and is encoded in utf8.
4. To distinguish between two identifier types
in the grammar, two Bison types were added:
<ident_cli> and <ident_sys>
5. All non-reserved keywords were marked as
being of the type <ident_cli>.
All reserved keywords are still of the type NONE.
6. All curly brackets in rules collecting
non-reserved keywords into non-terminal
symbols were removed, e.g.:
Was:
keyword_sp_data_type:
BIT_SYM {}
| BOOLEAN_SYM {}
Now:
keyword_sp_data_type:
BIT_SYM
| BOOLEAN_SYM
This is important NOT to have brackets here!!!!
This is needed to make sure that the underlying
Lex_ident_cli_ststructure correctly passes up to
the calling rule.
6. The code to scan identifiers and keywords
was moved from lex_one_token() into new
Lex_input_stream methods:
scan_ident_sysvar()
scan_ident_start()
scan_ident_middle()
scan_ident_delimited()
This was done to:
- get rid of enormous amount of references to &yylval->lex_str
- and remove a lot of references like lip->xxx
7. The allocating functionality which puts identifiers on the
THD memory root now resides in methods of Lex_ident_sys_st,
and in THD::to_ident_sys_alloc().
get_quoted_token() was removed.
8. Cleanup: check_simple_select() was moved as a method to LEX.
9. Cleanup: Some more functionality was moved from *.yy
to new methods were added to LEX:
make_item_colon_ident_ident()
make_item_func_call_generic()
create_item_qualified_asterisk()
These test can sporadically show mutex deadlock warnings between LOCK_wsrep_thd
and LOCK_thd_data mutexes. This means that these mutexes can be locked in opposite
order by different threads, and thus result in deadlock situation.
To fix such issue, the locking policy of these mutexes should be revised and
enforced to be uniform. However, a quick code review shows that the number of
lock/unlock operations for these mutexes combined is between 100-200, and all these
mutex invocations should be checked/fixed.
On the other hand, it turns out that LOCK_wsrep_thd is used for protecting access to
wsrep variables of THD (wsrep_conflict_state, wsrep_query_state), whereas LOCK_thd_data
protects query, db and mysys_var variables in THD. Extending LOCK_thd_data to protect
also wsrep variables looks like a viable solution, as there should not be a use case
where separate threads need simultaneous access to wsrep variables and THD data variables.
In this commit LOCK_wsrep_thd mutex is refactored to be replaced by LOCK_thd_data.
By bluntly replacing LOCK_wsrep_thd by LOCK_thd_data, will result in double locking
of LOCK_thd_data, and some adjustements have been performed to fix such situations.
ALTER TABLE ... ADD PARTITION modifies the open TABLE structure,
and sets table->need_reopen=1 to reset these modifications
in case of an error.
But under LOCK TABLES the table isn't get reopened, despite need_reopen.
Fixed by reopening need_reopen tables under LOCK TABLE.
numerous fixes for CREATE ... SELECT with system versioning:
In CREATE ... SELECT the table is created based on the result set,
field properties do not count. That is
* field invisibility is *not* copied over
* AS ROW START/END is *not* copied over
* the history is *not* copied over
* system row_start/row_end fields can *not* be created from the SELECT part
Methods:
- Item_user_var_as_out_param::print_for_load()
- sql_exchange::escaped_given(void)
Parameters:
- sql_exchange in write_execute_load_query_log_event()
- sql_exchange in mysql_load()
- sql_exchange in Load_log_event::Load_log_event()
Also, removing cast to "char*" in a few places in
Load_log_event::Load_log_event()
