Bug#4968 "Stored procedure crash if cursor opened on altered table"
Bug#19733 "Repeated alter, or repeated create/drop, fails"
Bug#19182 "CREATE TABLE bar (m INT) SELECT n FROM foo; doesn't work from
stored procedure."
Bug#6895 "Prepared Statements: ALTER TABLE DROP COLUMN does nothing"
Bug#22060 "ALTER TABLE x AUTO_INCREMENT=y in SP crashes server"
Test cases for bugs 4968, 19733, 6895 will be added in 5.0.
Re-execution of CREATE DATABASE, CREATE TABLE and ALTER TABLE
statements in stored routines or as prepared statements caused
incorrect results (and crashes in versions prior to 5.0.25).
In 5.1 the problem occured only for CREATE DATABASE, CREATE TABLE
SELECT and CREATE TABLE with INDEX/DATA DIRECTOY options).
The problem of bugs 4968, 19733, 19282 and 6895 was that functions
mysql_prepare_table, mysql_create_table and mysql_alter_table were not
re-execution friendly: during their operation they used to modify contents
of LEX (members create_info, alter_info, key_list, create_list),
thus making the LEX unusable for the next execution.
In particular, these functions removed processed columns and keys from
create_list, key_list and drop_list. Search the code in sql_table.cc
for drop_it.remove() and similar patterns to find evidence.
The fix is to supply to these functions a usable copy of each of the
above structures at every re-execution of an SQL statement.
To simplify memory management, LEX::key_list and LEX::create_list
were added to LEX::alter_info, a fresh copy of which is created for
every execution.
The problem of crashing bug 22060 stemmed from the fact that the above
metnioned functions were not only modifying HA_CREATE_INFO structure in
LEX, but also were changing it to point to areas in volatile memory of
the execution memory root.
The patch solves this problem by creating and using an on-stack
copy of HA_CREATE_INFO (note that code in 5.1 already creates and
uses a copy of this structure in mysql_create_table()/alter_table(),
but this approach didn't work well for CREATE TABLE SELECT statement).
Fixed compiler warnings (detected by VC++):
- Removed not used variables
- Added casts
- Fixed wrong assignments to bool
- Fixed wrong calls with bool arguments
- Added missing argument to store(longlong), which caused wrong store method to be called.
Note that we ignore CONCURRENT if LOAD DATA CONCURRENT is used from
inside a stored routine and MySQL is compiled with Query Cache support
(this is not in the manual).
The problem was that the condition test of "we are inside stored routine"
was reversed, thus CONCURRENT _worked only_ from stored routine. The
solution is to use proper condition test.
No test case is provided because the test case would require a large
amount of input, and it's hard to tell is SELECT is really blocked or
just slow (subject to race).
limitation)
Note to the reviewer
====================
Warning: reviewing this patch is somewhat involved.
Due to the nature of several issues all affecting the same area,
fixing separately each issue is not practical, since each fix can not be
implemented and tested independently.
In particular, the issues with
- rule recursion
- nested case statements
- forward jump resolution (backpatch list)
are tightly coupled (see below).
Definitions
===========
The expression
CASE expr
WHEN expr THEN expr
WHEN expr THEN expr
...
END
is a "Simple Case Expression".
The expression
CASE
WHEN expr THEN expr
WHEN expr THEN expr
...
END
is a "Searched Case Expression".
The statement
CASE expr
WHEN expr THEN stmts
WHEN expr THEN stmts
...
END CASE
is a "Simple Case Statement".
The statement
CASE
WHEN expr THEN stmts
WHEN expr THEN stmts
...
END CASE
is a "Searched Case Statement".
A "Left Recursive" rule is like
list:
element
| list element
;
A "Right Recursive" rule is like
list:
element
| element list
;
Left and right recursion produces the same language, the difference only
affects the *order* in which the text is parsed.
In a descendant parser (usually written manually), right recursion works
very well, and is typically implemented with a while loop.
In an ascendant parser (yacc/bison) left recursion works very well,
and is implemented naturally by the parser stack.
In both cases, using the wrong type or recursion is very bad and should be
avoided, as it causes technical issues with the parser implementation.
Before this change
==================
The "Simple Case Expression" and "Searched Case Expression" were both
implemented by the "when_list" and "when_list2" rules, which are left
recursive (ok).
These rules, however, used lex->when_list instead of using the parser stack,
which is more complex that necessary, and potentially dangerous because
of other rules using THD::reset_lex.
The "Simple Case Statement" and "Searched Case Statements" were implemented
by the "sp_case", "sp_whens" and in part by "sp_proc_stmt" rules.
Both cases were right recursive (bad).
The grammar involved was convoluted, and is assumed to be the results of
tweaks to get the code generation to work, but is not what someone would
naturally write.
In addition, using a common rule for both "Simple" and "Searched" case
statements was implemented with sp_head::m_flags |= IN_SIMPLE_CASE,
which is a flag and not a stack, and therefore does not take into account
*nested* case statements. This leads to incorrect generated code, and either
a server crash or an incorrect result.
With regards to the backpatch mechanism, a *different* backpatch list was
created for each jump from "WHEN expr THEN stmt" to "END CASE", which
relied on the grammar to be right recursive.
This is a mis-use of the backpatch list, since this list can resolve
multiple references to the same target at once.
The optimizer algorithm used to detect dead code in the "assembly" SQL
instructions, implemented by sp_head::opt_mark(uint ip), was recursive
in some cases (a conditional jump pointing forward to another conditional
jump).
In case of specially crafted code, like
- a long list of "IF expr THEN stmt END IF"
- a long CASE statement
this would actually cause a server crash with a stack overflow.
In general, having a stack that grows proportionally with user data (the
SQL code given by the client in a CREATE PROCEDURE) is to be avoided.
In debug builds only, creating a SP / SF / Trigger which had a significant
amount of code would spend --literally-- several minutes in sp_head::create,
because of the debug code involved with DBUG_PRINT("info", ("Code %s ...
There are several issues with this code:
- in a CASE with 5 000 WHEN, there are 15 000 instructions generated,
which create a sting representation of the code which is 500 000 bytes
long,
- using a String instead of an io stream causes performances to degrade
to a total server freeze, as time is spent doing realloc of a buffer
always too short,
- Printing a 500 000 long string in the debug log is too verbose,
- Generating this string even when DBUG_PRINT is off is useless,
- Having code that potentially can affect the server behavior, used with
#ifdef / #endif is useful in some cases, but is also a bad practice.
After this change
=================
"Case Expressions" (both simple and searched) have been simplified to
not use LEX::when_list, which has been removed.
Considering all the issues affecting case statements, the grammar for these
has been totally re written.
The existing actions, used to generate "assembly" sp_inst* code, have been
preserved but moved in the new grammar, with the following changes:
a) Bison rules are no longer shared between "Simple" and "Searched" case
statements, because a stack instead of a flag is required to handle them.
Nested statements are handled naturally by the parser stack, which by
definition uses the correct rule in the correct context.
Nested statements of the opposite type (simple vs searched) works correctly.
The flag sp_head::IN_SIMPLE_CASE is no longer used.
This is a step towards resolution of WL#2999, which correctly identified
that temporary parsing flags do not belong to sp_head.
The code in the action is shared by mean of the case_stmt_action_xxx()
helpers.
b) The backpatch mechanism, used to resolve forward jumps in the generated
code, has been changed to:
- create a label for the instruction following 'END CASE',
- register each jump at the end of a "WHEN expr THEN stmt" in a *unique*
backpatch list associated with the 'END CASE' label
- resolve all the forward jumps for this label at once.
In addition, the code involving backpatch has been commented, so that a
reader can now understand by reading matching "Registering" and "Resolving"
comments how the forward jumps are resolved and what target they resolve to,
as this is far from evident when reading the code alone.
The implementation of sp_head::opt_mark() has been revised to avoid
recursive calls from jump instructions, and instead add the jump location
to the list of paths to explore during the flow analysis of the instruction
graph, with a call to sp_head::add_mark_lead().
In addition, the flow analysis will stop if an instruction has already
been marked as reachable, which the previous code failed to do in the
recursive case.
sp_head::opt_mark() is now private, to prevent new calls to this method from
being introduced.
The debug code present in sp_head::create() has been removed.
Considering that SHOW PROCEDURE CODE is also available in debug builds,
and can be used anytime regardless of the trace level, as opposed to
"CREATE PROCEDURE" time and only if the trace was on,
removing the code actually makes debugging easier (usable trace).
Tests have been written to cover the parser overflow (big CASE),
and to cover nested CASE statements.
This change set implements the DROP TRIGGER IF EXISTS functionality.
This fix is considered a bug and not a feature, because without it,
there is no known method to write a database creation script that can create
a trigger without failing, when executed on a database that may or may not
contain already a trigger of the same name.
Implementing this functionality closes an orthogonality gap between triggers
and stored procedures / stored functions (which do support the DROP IF
EXISTS syntax).
In sql_trigger.cc, in mysql_create_or_drop_trigger,
the code has been reordered to:
- perform the tests that do not depend on the file system (access()),
- get the locks (wait_if_global_read_lock, LOCK_open)
- call access()
- perform the operation
- write to the binlog
- unlock (LOCK_open, start_waiting_global_read_lock)
This is to ensure that all the code that depends on the presence of the
trigger file is executed in the same critical section,
and prevents race conditions similar to the case fixed by Bug 14262 :
- thread 1 executes DROP TRIGGER IF EXISTS, access() returns a failure
- thread 2 executes CREATE TRIGGER
- thread 2 logs CREATE TRIGGER
- thread 1 logs DROP TRIGGER IF EXISTS
The patch itself is based on code contributed by the MySQL community,
under the terms of the Contributor License Agreement (See Bug 18161).
select OK.
The SQL parser was using Item::name to transfer user defined function attributes
to the user defined function (udf). It was not distinguishing between user defined
function call arguments and stored procedure call arguments. Setting Item::name
was causing Item_ref::print() method to print the argument as quoted identifiers
and caused views that reference aggregate functions as udf call arguments (and
rely on Item::print() for the text of the view to store) to throw an undefined
identifier error.
Overloaded Item_ref::print to print aggregate functions as such when printing
the references to aggregate functions taken out of context by split_sum_func2()
Fixed the parser to properly detect using AS clause in stored procedure arguments
as an error.
Fixed printing the arguments of udf call to print properly the udf attribute.
should fail to create
The problem was that this type of errors was checked during view
creation, which doesn't happen when CREATE VIEW is a statement of
a created stored routine.
The solution is to perform the checks at parse time. The idea of the
fix is that the parser checks if a construction just parsed is allowed
in current circumstances by testing certain flags, and this flags are
reset for VIEWs.
The side effect of this change is that if the user already have
such bogus routines, it will now get a error when trying to do
SHOW CREATE PROCEDURE proc;
(and some other) and when trying to execute such routine he will get
ERROR 1457 (HY000): Failed to load routine test.p5. The table mysql.proc is missing, corrupt, or contains bad data (internal code -6)
However there should be very few such users (if any), and they may
(and should) drop these bogus routines.
The syntax of the CALL statement, to invoke a stored procedure, has been
changed to make the use of parenthesis optional in the argument list.
With this change, "CALL p;" is equivalent to "CALL p();".
While the SQL spec does not explicitely mandate this syntax, supporting it
is needed for practical reasons, for integration with JDBC / ODBC connectors.
Also, warnings in the sql/sql_yacc.yy file, which were not reported by Bison 2.1
but are now reported by Bison 2.2, have been fixed.
The warning found were:
bison -y -p MYSQL -d --debug --verbose sql_yacc.yy
sql_yacc.yy:653.9-18: warning: symbol UNLOCK_SYM redeclared
sql_yacc.yy:656.9-17: warning: symbol UNTIL_SYM redeclared
sql_yacc.yy:658.9-18: warning: symbol UPDATE_SYM redeclared
sql_yacc.yy:5169.11-5174.11: warning: unused value: $2
sql_yacc.yy:5208.11-5220.11: warning: unused value: $5
sql_yacc.yy:5221.11-5234.11: warning: unused value: $5
conflicts: 249 shift/reduce
"unused value: $2" correspond to the $$=$1 assignment in the 1st {} block
in table_ref -> join_table {} {},
which does not procude a result ($$) for the rule but an intermediate $2
value for the action instead.
"unused value: $5" are similar, with $$ assignments in {} actions blocks
which are not for the final reduce.
Presence of a subquery in the ON expression of a join
should not block merging the view that contains this join.
Before this patch the such views were converted into
into temporary table views.
1003: Incorrect table name
in multi-table DELETE the set of tables to delete from actually
references then tables in the other list, e.g:
DELETE alias_of_t1 FROM t1 alias_of_t1 WHERE ....
is a valid statement.
So we must turn off table name syntactical validity check for alias_of_t1
because it's not a table name (even if it looks like one).
In order to do that we add a special flag (TL_OPTION_ALIAS) to
disable the name checking for the aliases in multi-table DELETE.
make st_select_lex::setup_ref_array() take into account that
Item_sum-descendant objects located within descendant SELECTs
may be added into ref_pointer_array.
Made the parser to support parenthesis around UNION branches.
This is done by amending the rules of the parser so it generates the correct
structure.
Currently it supports arbitrary subquery/join/parenthesis operations in the
EXISTS clause.
In the IN/scalar subquery case it will allow adding nested parenthesis only
if there is an UNION clause after the parenthesis. Otherwise it will just
treat the multiple nested parenthesis as a scalar expression.
It adds extra lex level for ((SELECT ...) UNION ...) to accommodate for the
UNION clause.
erroneous check
Problem: Actually there were two problems in the server code. The check
for SQLCOM_FLUSH in SF/Triggers were not according to the existing
architecture which uses sp_get_flags_for_command() from sp_head.cc .
This function was also missing a check for SQLCOM_FLUSH which has a
problem combined with prelocking. This changeset fixes both of these
deficiencies as well as the erroneous check in
sp_head::is_not_allowed_in_function() which was a copy&paste error.
User name (host name) has limit on length. The server code relies on these
limits when storing the names. The problem was that sometimes these limits
were not checked properly, so that could lead to buffer overflow.
The fix is to check length of user/host name in parser and if string is too
long, throw an error.
- if there are two character set definitions in the column declaration,
we replace the first one with the second one as we store both in the LEX->charset
slot. Add a separate slot to the LEX structure to store underscore charset.
- convert default values to the column charset of STRING, VARSTRING fields
if necessary as well.
