The crash happened with an indexed virtual column whose
value is evaluated using a function that has a different meaning
in sql_mode='' vs sql_mode=ORACLE:
- DECODE()
- LTRIM()
- RTRIM()
- LPAD()
- RPAD()
- REPLACE()
- SUBSTR()
For example:
CREATE TABLE t1 (
b VARCHAR(1),
g CHAR(1) GENERATED ALWAYS AS (SUBSTR(b,0,0)) VIRTUAL,
KEY g(g)
);
So far we had replacement XXX_ORACLE() functions for all mentioned function,
e.g. SUBSTR_ORACLE() for SUBSTR(). So it was possible to correctly re-parse
SUBSTR_ORACLE() even in sql_mode=''.
But it was not possible to re-parse the MariaDB version of SUBSTR()
after switching to sql_mode=ORACLE. It was erroneously mis-interpreted
as SUBSTR_ORACLE().
As a result, this combination worked fine:
SET sql_mode=ORACLE;
CREATE TABLE t1 ... g CHAR(1) GENERATED ALWAYS AS (SUBSTR(b,0,0)) VIRTUAL, ...;
INSERT ...
FLUSH TABLES;
SET sql_mode='';
INSERT ...
But the other way around it crashed:
SET sql_mode='';
CREATE TABLE t1 ... g CHAR(1) GENERATED ALWAYS AS (SUBSTR(b,0,0)) VIRTUAL, ...;
INSERT ...
FLUSH TABLES;
SET sql_mode=ORACLE;
INSERT ...
At CREATE time, SUBSTR was instantiated as Item_func_substr and printed
in the FRM file as substr(). At re-open time with sql_mode=ORACLE, "substr()"
was erroneously instantiated as Item_func_substr_oracle.
Fix:
The fix proposes a symmetric solution. It provides a way to re-parse reliably
all sql_mode dependent functions to their original CREATE TABLE time meaning,
no matter what the open-time sql_mode is.
We take advantage of the same idea we previously used to resolve sql_mode
dependent data types.
Now all sql_mode dependent functions are printed by SHOW using a schema
qualifier when the current sql_mode differs from the function sql_mode:
SET sql_mode='';
CREATE TABLE t1 ... SUBSTR(a,b,c) ..;
SET sql_mode=ORACLE;
SHOW CREATE TABLE t1; -> mariadb_schema.substr(a,b,c)
SET sql_mode=ORACLE;
CREATE TABLE t2 ... SUBSTR(a,b,c) ..;
SET sql_mode='';
SHOW CREATE TABLE t1; -> oracle_schema.substr(a,b,c)
Old replacement names like substr_oracle() are still understood for
backward compatibility and used in FRM files (for downgrade compatibility),
but they are not printed by SHOW any more.
This commit addresses column naming issues with CTEs in the use of prepared
statements and stored procedures. Usage of either prepared statements or
procedures with Common Table Expressions and column renaming may be affected.
There are three related but different issues addressed here.
1) First execution issue. Consider the following
prepare s from "with cte (col1, col2) as (select a as c1, b as c2 from t
order by c1) select col1, col2 from cte";
execute s;
After parsing, items in the select are named (c1,c2), order by (and group by)
resolution is performed, then item names are set to (col1, col2).
When the statement is executed, context analysis is again performed, but
resolution of elements in the order by statement will not be able to find c1,
because it was renamed to col1 and remains this way.
The solution is to save the names of these items during context resolution
before they have been renamed. We can then reset item names back to those after
parsing so first execution can resolve items referred to in order and group by
clauses.
2) Second Execution Issue
When the derived table contains more than one select 'unioned' together we could
reasonably think that dealing with only items in the first select (which
determines names in the resultant table) would be sufficient. This can lead to
a different problem. Consider
prepare st from "with cte (c1,c2) as
(select a as col1, sum(b) as col2 from t1 where a > 0 group by col1
union select a as col3, sum(b) as col4 from t2 where b > 2 group by col3)
select * from cte where c1=1";
When the optimizer (only run during the first execution) pushes the outside
condition "c1=1" into every select in the derived table union, it renames the
items to make the condition valid. In this example, this leaves the first item
in the second select named 'c1'. The second execution will now fail 'group by'
resolution.
Again, the solution is to save the names during context analysis, resetting
before subsequent resolution, but making sure that we save/reset the item
names in all the selects in this union.
3) Memory Leak
During parsing Item::set_name() is used to allocate memory in the statement
arena. We cannot use this call during statement execution as this represents
a memory leak. We directly set the item list names to those in the column list
of this CTE (also allocated during parsing).
Approved by Igor Babaev <igor@mariadb.com>
An "ITERATE innerLoop" did not work properly inside
a WHILE loop, which itself is inside an outer FOR loop:
outerLoop:
FOR
...
innerLoop:
WHILE
...
ITERATE innerLoop;
...
END WHILE;
...
END FOR;
It erroneously generated an integer increment code for the outer FOR loop.
There were two problems:
1. "ITERATE innerLoop" worked like "ITERATE outerLoop"
2. It was always integer increment, even in case of FOR cursor loops.
Background:
- A FOR loop automatically creates a dedicated sp_pcontext stack entry,
to put the iteration and bound variables on it.
- Other loop types (LOOP, WHILE, REPEAT), do not generate a dedicated
slack entry.
The old code erroneously assumed that sp_pcontext::m_for_loop
either describes the most inner loop (in case the inner loop is FOR),
or is empty (in case the inner loop is not FOR).
But in fact, sp_pcontext::m_for_loop is never empty inside a FOR loop:
it describes the closest FOR loop, even if this FOR loop has nested
non-FOR loops inside.
So when we're near the ITERATE statement in the above script,
sp_pcontext::m_for_loop is not empty - it stores information about
the FOR loop labeled as "outrLoop:".
Fix:
- Adding a new member sp_pcontext::Lex_for_loop::m_start_label,
to remember the explicit or the auto-generated label correspoding
to the start of the FOR body. It's used during generation
of "ITERATE loop_label" code to check if "loop_label" belongs
to the current FOR loop pointed by sp_pcontext::m_for_loop,
or belongs to a non-FOR nested loop.
- Adding LEX methods sp_for_loop_intrange_iterate() and
sp_for_loop_cursor_iterate() to reuse the code between
methods handling:
* ITERATE
* END FOR
- Adding a test for Lex_for_loop::is_for_loop_cursor()
and generate a code either a cursor fetch, or for an integer increment.
Before this change, it always erroneously generated an integer increment
version.
- Cleanup: Initialize Lex_for_loop_st::m_cursor_offset inside
Lex_for_loop_st::init(), to avoid not initialized members.
- Cleanup: Removing a redundant method:
Lex_for_loop_st::init(const Lex_for_loop_st &other)
Using Lex_for_loop_st::operator(const Lex_for_loop_st &other) instead.
The function setup_windows() called at the prepare phase of processing a
select builds a list of all window specifications used in the select. This list
is built on the statement memory and it must be done only once.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
Adding virtual methods to class Schema:
make_item_func_replace()
make_item_func_substr()
make_item_func_trim()
This is a non-functional preparatory change for MDEV-27744.
EXPLAIN EXTENDED for an UPDATE/DELETE/INSERT/REPLACE statement did not
produce the warning containing the text representation of the query
obtained after the optimization phase. Such warning was produced for
SELECT statements, but not for DML statements.
The patch fixes this defect of EXPLAIN EXTENDED for DML statements.
MDEV-30668 Set function aggregated in outer select used in view definition
This patch fixes two bugs concerning views whose specifications contain
subqueries with set functions aggregated in outer selects.
Due to the first bug those such views that have implicit grouping were
considered as mergeable. This led to wrong result sets for selects from
these views.
Due to the second bug the aggregation select was determined incorrectly and
this led to bogus error messages.
The patch added several test cases for these two bugs and for four other
duplicate bugs.
The patch also enables view-protocol for many other test cases.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
Subselect_single_value_engine cannot handle table value constructor used as
subquery. That's why any table value constructor TVC used as subquery is
converted into a select over derived table whose specification is TVC.
Currently the names of the columns of the derived table DT are taken from
the first element of TVC and if the k-th component of the element happens
to be a subquery the text representation of this subquery serves as the
name of the k-th column of the derived table. References of all columns of
the derived table DT compose the select list of the result of the conversion.
If a definition of a view contained a table value constructor used as a
subquery and the view was registered after this conversion had been
applied we could register an invalid view definition if the first element
of TVC contained a subquery as its component: the name of this component
was taken from the original subquery, while the name of the corresponding
column of the derived table was taken from the text representation of the
subquery produced by the function SELECT_LEX::print() and these names were
usually differ from each other.
To avoid registration of such invalid views the function SELECT_LEX::print()
now prints the original TVC instead of the select in which this TVC has
been wrapped. Now the specification of registered view looks like as if no
conversions from TVC to selects were done.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
This patch is the result of running
run-clang-tidy -fix -header-filter=.* -checks='-*,modernize-use-equals-default' .
Code style changes have been done on top. The result of this change
leads to the following improvements:
1. Binary size reduction.
* For a -DBUILD_CONFIG=mysql_release build, the binary size is reduced by
~400kb.
* A raw -DCMAKE_BUILD_TYPE=Release reduces the binary size by ~1.4kb.
2. Compiler can better understand the intent of the code, thus it leads
to more optimization possibilities. Additionally it enabled detecting
unused variables that had an empty default constructor but not marked
so explicitly.
Particular change required following this patch in sql/opt_range.cc
result_keys, an unused template class Bitmap now correctly issues
unused variable warnings.
Setting Bitmap template class constructor to default allows the compiler
to identify that there are no side-effects when instantiating the class.
Previously the compiler could not issue the warning as it assumed Bitmap
class (being a template) would not be performing a NO-OP for its default
constructor. This prevented the "unused variable warning".
This patch fixes the patch for bug MDEV-30248 that unsatisfactorily
resolved the problem of resolution of references to CTE. In some cases
when such a reference has the same table name as the name of one of
CTEs containing this reference the reference could be resolved incorrectly
that led to an invalid select tree where units could be mutually dependent.
This in its turn could lead to an infinite sequence of recursive calls or
to falls into infinite loops.
The patch also removes LEX::resolve_references_to_cte_in_hanging_cte() as
with the new code for resolution of CTE references the call of this
function is not needed anymore.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
Use SELECT_LEX to save lists for ORDER BY and GROUP BY before parsing
WINDOW clauses / specifications. This is needed for proper parsing
of a nested WINDOW clause when a WINDOW clause is used in a subquery
contained in another WINDOW clause.
Fix assignment of empty SQL_I_List to another one (in case of empty list
next shoud point on first).
Nowdays subquery in a UNION's ORDER BY placed correctly in fake select,
the only problem was incorrect Name_resolution_contect is fixed by this
patch in parsing, so we do not need scanning/reseting of ORDER BY of
a union.
empty identifier specified as `` ends up with a NULL LEX_CSTRING::str in lexer.
This is not considered correct in upper layers, for example in Compare_identifiers::operator().
Empty column name is usually avoided by a check_column_name() call while parsing,
and period name matches the column name completely.
Hence, this fix uses the mentioned call for verification, too.
Remove table_count from Query_tables_list (not used, moved to MYSQL_LOCK).
Rename table_count from LEX to avoid mixing it with other counters of tables.
Running some statements that use IN subqueries outside context of a regular
query could result in server abnormal termination.
The reason for failure is that internal structures SELECT_LEX/SELECT_LEX_UNIT
created on behalf of parsed query were initialized incorrectly. Incorrect
initialization of the structures SELECT_LEX/SELECT_LEX_UNIT was introduced
by the commit de745ecf29
(MDEV-11953: support of brackets in UNION/EXCEPT/INTERSECT operations)
pushed into 10.4, that is the reason this bug report is not reproduced in 10.3.
To fix the issue the method SLECTE_LEX::register_unit is used for proper
initialization of the data structures SELECT_LEX/SELECT_LEX_UNIT. Additionally,
the method SELECT_LEX::get_slave() was removed from the source code base
since for those use cases where it is used it can be replaced by the method
first_inner_unit().
This patch corrects the fix for MDEV-26412.
Note that when parsing an ON expression the pointer to the current select
is always in select_stack[select_stack_top - 1]. So the pointer to the
outer select (if any) is in select_stack[select_stack_top - 2].
The query manifesting this bug is added to the test case of MDEV-26412.
Moved LIMIT warning from vers_set_hist_part() to new call
vers_check_limit() at table unlock phase. At that point
read_partitions bitmap is already pruned by DML code (see
prune_partitions(), find_used_partitions()) so we have to set
corresponding bits for working history partition.
Also we don't do my_error(ME_WARNING|ME_ERROR_LOG), because at that
point it doesn't update warnings number, so command reports 0 warnings
(but warning list is still updated). Instead we do
push_warning_printf() and sql_print_warning() separately.
Under LOCK TABLES external_lock(F_UNLCK) is not executed. There is
start_stmt(), but no corresponding "stop_stmt()". So for that mode we
call vers_check_limit() directly from close_thread_tables().
Test result has been changed according to new LIMIT and warning
printing algorithm. For convenience all LIMIT warnings are marked with
"You see warning above ^".
TODO MDEV-20345 fixed. Now vers_history_generating() contains
fine-grained list of DML-commands that can generate history (and TODO
mechanism worked well).
IF an INSERT/REPLACE SELECT statement contained an ON expression in the top
level select and this expression used a subquery with a column reference
that could not be resolved then an attempt to resolve this reference as
an outer reference caused a crash of the server. This happened because the
outer context field in the Name_resolution_context structure was not set
to NULL for such references. Rather it pointed to the first element in
the select_stack.
Note that starting from 10.4 we cannot use the SELECT_LEX::outer_select()
method when parsing a SELECT construct.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
The first step for deprecating innodb_autoinc_lock_mode(see MDEV-27844) is:
- to switch statement binlog format to ROW if binlog format is MIXED and
the statement changes autoincremented fields
- issue warnings if innodb_autoinc_lock_mode == 2 and binlog format is
STATEMENT
failed in Diagnostics_area::set_ok_status in my_ok from
mysql_sql_stmt_prepare
Analysis: Before PREPARE is executed, binlog_format is STATEMENT.
This PREPARE had SET STATEMENT which sets binlog_format to ROW. Now after
PREPARE is done we reset the binlog_format (back to STATEMENT). But we have
temporary table, it doesn't let changing binlog_format=ROW to
binlog_format=STATEMENT and gives error which goes unreported. This
unreported error eventually causes assertion failure.
Fix: Change return type for LEX::restore_set_statement_var() to bool and
make it return error state.
If the first token of the body of a stored procedure was 'WITH' then
the beginning of the body was determined incorrectly and that token was
missing in the string representing the body of the SP in mysql.proc. As a
resultnany call of such procedure failed as the string representing the
body could not be parsed.
The patch corrects the code of the functions get_tok_start() and
get_cpp_tok_start() of the class Lex_input_stream to make them take into
account look ahead tokens. The patch is needed only for 10.2 as this
problem has neen resolved in 10.3+.
In the code existed just before this patch binding of a table reference to
the specification of the corresponding CTE happens in the function
open_and_process_table(). If the table reference is not the first in the
query the specification is cloned in the same way as the specification of
a view is cloned for any reference of the view. This works fine for
standalone queries, but does not work for stored procedures / functions
for the following reason.
When the first call of a stored procedure/ function SP is processed the
body of SP is parsed. When a query of SP is parsed the info on each
encountered table reference is put into a TABLE_LIST object linked into
a global chain associated with the query. When parsing of the query is
finished the basic info on the table references from this chain except
table references to derived tables and information schema tables is put
in one hash table associated with SP. When parsing of the body of SP is
finished this hash table is used to construct TABLE_LIST objects for all
table references mentioned in SP and link them into the list of such
objects passed to a pre-locking process that calls open_and_process_table()
for each table from the list.
When a TABLE_LIST for a view is encountered the view is opened and its
specification is parsed. For any table reference occurred in
the specification a new TABLE_LIST object is created to be included into
the list for pre-locking. After all objects in the pre-locking have been
looked through the tables mentioned in the list are locked. Note that the
objects referenced CTEs are just skipped here as it is impossible to
resolve these references without any info on the context where they occur.
Now the statements from the body of SP are executed one by one that.
At the very beginning of the execution of a query the tables used in the
query are opened and open_and_process_table() now is called for each table
reference mentioned in the list of TABLE_LIST objects associated with the
query that was built when the query was parsed.
For each table reference first the reference is checked against CTEs
definitions in whose scope it occurred. If such definition is found the
reference is considered resolved and if this is not the first reference
to the found CTE the the specification of the CTE is re-parsed and the
result of the parsing is added to the parsing tree of the query as a
sub-tree. If this sub-tree contains table references to other tables they
are added to the list of TABLE_LIST objects associated with the query in
order the referenced tables to be opened. When the procedure that opens
the tables comes to the TABLE_LIST object created for a non-first
reference to a CTE it discovers that the referenced table instance is not
locked and reports an error.
Thus processing non-first table references to a CTE similar to how
references to view are processed does not work for queries used in stored
procedures / functions. And the main problem is that the current
pre-locking mechanism employed for stored procedures / functions does not
allow to save the context in which a CTE reference occur. It's not trivial
to save the info about the context where a CTE reference occurs while the
resolution of the table reference cannot be done without this context and
consequentially the specification for the table reference cannot be
determined.
This patch solves the above problem by moving resolution of all CTE
references at the parsing stage. More exactly references to CTEs occurred in
a query are resolved right after parsing of the query has finished. After
resolution any CTE reference it is marked as a reference to to derived
table. So it is excluded from the hash table created for pre-locking used
base tables and view when the first call of a stored procedure / function
is processed.
This solution required recursive calls of the parser. The function
THD::sql_parser() has been added specifically for recursive invocations of
the parser.
In the code existed just before this patch binding of a table reference to
the specification of the corresponding CTE happens in the function
open_and_process_table(). If the table reference is not the first in the
query the specification is cloned in the same way as the specification of
a view is cloned for any reference of the view. This works fine for
standalone queries, but does not work for stored procedures / functions
for the following reason.
When the first call of a stored procedure/ function SP is processed the
body of SP is parsed. When a query of SP is parsed the info on each
encountered table reference is put into a TABLE_LIST object linked into
a global chain associated with the query. When parsing of the query is
finished the basic info on the table references from this chain except
table references to derived tables and information schema tables is put
in one hash table associated with SP. When parsing of the body of SP is
finished this hash table is used to construct TABLE_LIST objects for all
table references mentioned in SP and link them into the list of such
objects passed to a pre-locking process that calls open_and_process_table()
for each table from the list.
When a TABLE_LIST for a view is encountered the view is opened and its
specification is parsed. For any table reference occurred in
the specification a new TABLE_LIST object is created to be included into
the list for pre-locking. After all objects in the pre-locking have been
looked through the tables mentioned in the list are locked. Note that the
objects referenced CTEs are just skipped here as it is impossible to
resolve these references without any info on the context where they occur.
Now the statements from the body of SP are executed one by one that.
At the very beginning of the execution of a query the tables used in the
query are opened and open_and_process_table() now is called for each table
reference mentioned in the list of TABLE_LIST objects associated with the
query that was built when the query was parsed.
For each table reference first the reference is checked against CTEs
definitions in whose scope it occurred. If such definition is found the
reference is considered resolved and if this is not the first reference
to the found CTE the the specification of the CTE is re-parsed and the
result of the parsing is added to the parsing tree of the query as a
sub-tree. If this sub-tree contains table references to other tables they
are added to the list of TABLE_LIST objects associated with the query in
order the referenced tables to be opened. When the procedure that opens
the tables comes to the TABLE_LIST object created for a non-first
reference to a CTE it discovers that the referenced table instance is not
locked and reports an error.
Thus processing non-first table references to a CTE similar to how
references to view are processed does not work for queries used in stored
procedures / functions. And the main problem is that the current
pre-locking mechanism employed for stored procedures / functions does not
allow to save the context in which a CTE reference occur. It's not trivial
to save the info about the context where a CTE reference occurs while the
resolution of the table reference cannot be done without this context and
consequentially the specification for the table reference cannot be
determined.
This patch solves the above problem by moving resolution of all CTE
references at the parsing stage. More exactly references to CTEs occurred in
a query are resolved right after parsing of the query has finished. After
resolution any CTE reference it is marked as a reference to to derived
table. So it is excluded from the hash table created for pre-locking used
base tables and view when the first call of a stored procedure / function
is processed.
This solution required recursive calls of the parser. The function
THD::sql_parser() has been added specifically for recursive invocations of
the parser.
plugin variables in SET only locked the plugin till the end of the
statement. If SET with a plugin variable was prepared, it was possible
to uninstall the plugin before EXECUTE. Then EXECUTE would crash,
trying to resolve a now-invalid pointer to a disappeared variable.
Fix: keep plugins locked until the prepared statement is closed.
Before FRM is written walk vcol expressions through
check_table_name_processor() and check if field items match (db,
table_name) qualifier.
We cannot do this in check_vcol_func_processor() as there is already
no table name qualifiers in expressions of written and loaded FRM.
Before this patch mergeable derived tables / view used in a multi-table
update / delete were merged before the preparation stage.
When the merge of a derived table / view is performed the on expression
attached to it is fixed and ANDed with the where condition of the select S
containing this derived table / view. It happens after the specification of
the derived table / view has been merged into S. If the ON expression refers
to a non existing field an error is reported and some other mergeable derived
tables / views remain unmerged. It's not a problem if the multi-table
update / delete statement is standalone. Yet if it is used in a stored
procedure the select with incompletely merged derived tables / views may
cause a problem for the second call of the procedure. This does not happen
for select queries using derived tables / views, because in this case their
specifications are merged after the preparation stage at which all ON
expressions are fixed.
This patch makes sure that merging of the derived tables / views used in a
multi-table update / delete statement is performed after the preparation
stage.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
At the second execution of the PS
1. mark_as_dependent() is called with the same parameters as at the first
execution (select#4 and select#3)
2. as outer_select (select#3) has been already merged at the first
execution of PS it cannot be reached using the outer_select() function
anymore (and so can not stop iteration).
3. as a result all selects towards the top level select including the
select for 'ca' are marked as uncacheable.
4. Marked uncacheable it executed incorrectly triggering filling its
temporary table several times and using freed memory at the end.
To avoid the problem we use name resolution context to go "up".
NOTE: problem also exists in 10.2 but has no visible effect on execution.
That is why the problem is fixed in 10.2.
The patch also add debug logging of important procedures and
better specify parameters types of st_select_lex::mark_as_dependent.
The bug caused crashes of the server when processing queries with nested
table value constructors (TVC) . It happened because the grammar rules to
parse TVC used the same global lists for both nested TVC and nesting TVC.
As a result invalid select trees were constructed for queries with nested
TVC and this led to crashes at the prepare stage.
This patch provides its own lists structures for each TVC nest level.
Besides the patch fixes a bug in the function wrap_tvc() that missed
inheritance of the SELECT_LEX::exclude_from_table_unique_test for
selects that wrapped TVCs. This inheritance is critical for specifications
of derived tables that employ nested TVCs.
Approved by dmitry.shulga@mariadb.com
