- Removing two copies of the drop_routine.
Adding a shared and much simplified version.
- Removing LEX metods:
bool stmt_drop_function(const DDL_options_st &options,
const Lex_ident_sys_st &db,
const Lex_ident_sys_st &name);
bool stmt_drop_function(const DDL_options_st &options,
const Lex_ident_sys_st &name);
bool stmt_drop_procedure(const DDL_options_st &options,
sp_name *name);
The code inside the methods was very similar.
Adding one method instead:
bool stmt_drop_routine(const Sp_handler *sph,
const DDL_options_st &options,
const Lex_ident_sys_st &db,
const Lex_ident_sys_st &name);
- Adding a new virtual method Sp_handler:sqlcom_drop().
It helped to unify the code inside the new stmt_drop_routine().
Problem:
Under terms of MDEV-27490, we'll update Unicode version used
to compare identifiers to 14.0.0. Unlike in the old Unicode version,
in the new version a string can grow during lower-case. We cannot
perform check_db_name() inplace any more.
Change summary:
- Allocate memory to store lower-cased identifiers in memory root
- Removing check_db_name() performing both in-place lower-casing and validation
at the same time. Splitting it into two separate stages:
* creating a memory-root lower-cased copy of an identifier
(using new MEM_ROOT functions and Query_arena wrapper methods)
* performing validation on a constant string
(using Lex_ident_fs methods)
Implementation details:
- Adding a mysys helper function to allocate lower-cased strings on MEM_ROOT:
lex_string_casedn_root()
and a Query_arena wrappers for it:
make_ident_casedn()
make_ident_opt_casedn()
- Adding a Query_arena method to perform both MEM_ROOT lower-casing and
database name validation at the same time:
to_ident_db_internal_with_error()
This method is very close to the old (pre-11.3) check_db_name(),
but performs lower-casing to a newly allocated MEM_ROOT
memory (instead of performing lower-casing the original string in-place).
- Adding a Table_ident method which additionally handles derived table names:
to_ident_db_internal_with_error()
- Removing the old check_db_name()
- Moving some of Database_qualidied_name methods into a new class
Identifier_chain2.
- Changing the data type of the following variables from
Database_qualified_name to Identifier_chain2:
* q_pkg_proc in LEX::call_statement_start()
* q_pkg_func in LEX::make_item_func_call_generic()
Rationale:
The data type of Database_qualified_name::m_db will be changed
to Lex_ident_db soon. So Database_qualified_name won't be able
to store the `pkg.routine` part of `db.pkg.routine` any more,
because `pkg` must not depend on lower-case-table-names.
Changing LEX_CSTRING* parameters of LEX::make_sp_name() to Lex_ident_sys_st.
This makes the code clear because a value of Lex_ident_sys_st has
some guaranteed additional constraints over a base LEX_CSTRING:
- Its LEX_CSTRING::str is not NULL (sql_yacc.yy would abort otherwise)
- Its LEX_CSTRING::str is 0-terminated
- Its a valid utf8 string
- The string pointed by LEX_CSTRING::str was created on THD::mem_root
Also changing "pass by pointer" to "pass by reference",
as these parameters can never be NULL - they are Bison stack variables.
Before this patch, the code in Item_field::print() used
this convention (described in sql_explain.h:ExplainDataStructureLifetime):
- By default, the table that Item_field refers to is accessible.
- ANALYZE and SHOW {EXPLAIN|ANALYZE} may print Items after some
temporary tables have been dropped. They use
QT_DONT_ACCESS_TMP_TABLES flag. When it is ON, Item_field::print
will not access the table it refers to, if it is a temp.table
The bug was that EXPLAIN statement also may compute subqueries (depending
on subquery context and @@expensive_subquery_limit setting). After the
computation, the subquery calls JOIN::cleanup(true) which drops some of
its temporary tables. Calling Item_field::print() that refer to such table
will cause an access to free'd memory.
In this patch, we take into account that query optimization can compute
a subquery and discard its temporary tables. Item_field::print() now
assumes that any temporary table might have already been dropped.
This means QT_DONT_ACCESS_TMP_TABLES flag is not needed - we imply it is
always present.
But we also make one exception: derived tables are not freed in
JOIN::cleanup() call. They are freed later in close_thread_tables(),
at the same time when regular tables are closed.
Because of that, Item_field::print may assume that temp.tables
representing derived tables are available.
Initial patch by: Rex Jonston
Reviewed by: Monty <monty@mariadb.org>
ANALYZE FORMAT=JSON output now includes table.r_engine_stats which
has the engine statistics. Only non-zero members are printed.
Internally: EXPLAIN data structures Explain_table_acccess and
Explain_update now have handler* handler_for_stats pointer.
It is used to read statistics from handler_for_stats->handler_stats.
The following applies only to 10.9+, backport doesn't use it:
Explain data structures exist after the tables are closed. We avoid
walking invalid pointers using this:
- SQL layer calls Explain_query::notify_tables_are_closed() before
closing tables.
- After that call, printing of JSON output is disabled. Non-JSON output
can be printed but we don't access handler_for_stats when doing that.
Fixed memory leakage taken place on execution of the statement
SHOW CREATE PACKAGE `pkg_name`
The memory leak was caused by implementation of sp_compile()
where a memory root for a stored routine was allocated but
a pointer to the new memory root wasn't passed to sp_package::create
for subsequent forwarding to the constructor of sp_package.
Instead, another one memory root was allocated and the pointer to
the original memory root was missed.
Re-designed a way by that Item_trigger_field objects are arranged in memory.
Item_trigger_field objects created on parsing a trigger's statement
is now stored in a per statement list. All lists of Item_trigger_field
objects created on parsing the whole trigger's body are organized
in the structure "list of lists". So, use binary cycle to iterate every
Item_trigger_field object created on parsing a trigger body.
To organize the data structure 'list of lists' the new data member
Item_trigger_field::next_trig_field_list
is introduced that links lists in this hierarchy structure.
This re-design is performed in order to avoid refences to already
deleted items on re-compilation of failed trigger's statememt.
Referencing to already deleted items could take place on re-parsing
a trigger's statement since every Item created for a statement
being re-parsed is deleted before the statement be re-parsed,
but deleted items are still referenced from sp_head. So, to avoid
access to dangling references a per statement list of Item_trigger_field
objects are cleared right after the current SP statement be cleaned up
and before re-parsing be started.
Added re-parsing of failed statements inside a stored routine.
General idea of the patch is to install an instance of the class
Reprepare_observer before executing a next SP instruction and
re-parse a statement of this SP instruction in case of
its execution failure.
To implement the described approach the class sp_lex_keeper
has been extended with the method validate_lex_and_exec_core()
that is just a wrapper around the method reset_lex_and_exec_core()
with additional setting/resetting an instance of the class
Reprepare_observer on each iteration of SP instruction
execution.
If reset_lex_and_exec_core() returns error and an instance
of the class Reprepare_observer is installed before running
a SP instruction then a number of attempts to re-run the SP
instruction is checked against a max. limit and in case it doesn't
reach the limit a statement for the failed SP instruction is re-parsed.
Re-parsing of a statement for the failed SP instruction is implemented
by the new method sp_le_inst::parse_expr() that prepends
a SP instruction's statement with the clause 'SELECT' and parse it.
Own SP instruction MEM_ROOT and a separate free_list is used for
parsing of a SP statement. On successful re-parsing of SP instruction's
statement the virtual methods adjust_sql_command() and
on_after_expr_parsing() of the class sp_lex_instr is called
to update the SP instruction state with a new data created
on parsing the statement.
Few words about reason for prepending a SP instruction's statement
with the clause 'SELECT' - this is required step to produce a valid
SQL statement, since for some SP instructions the instructions statement
is not a valid SQL statement. Wrapping such text into 'SELECT ( )'
produces a correct operator from SQL syntax point of view.
For those SP instructions that need to get access to ia LEX object
on execution, added storing of their original sql expressions inside
classes derived from the class sp_lex_instr.
A stored sql expression is returned by the abstract method
sp_lex_instr::get_expr_query
redefined in derived classes.
Since an expression constituting a SP instruction can be invalid
SQL statement in general case (not parseable statement), the virtual
method sp_lex_instr::get_query() is introduced to return a valid string
for a statement that corresponds to the given instruction.
Additionally, introduced the rule remember_start_opt in the grammar.
The new rule intended to get correct position of a current
token taking into attention the fact whether lookahead was done or not.
This is the prerequisite patch to move the data member
LEX::trg_table_fields to the class sp_head and rename it as
m_trg_table_fields.
This data member is used for handling OLD/NEW pseudo-rows inside
a trigger body and in order to be able to re-parse a trigger body
the data member must be moved from the struct LEX to the class sp_head.
This is the prerequisite patch to move the sp_instr class and classes derived
from it into the files sp_instr.cc/sp_instr.h. The classes sp_lex_cursor and
sp_lex_keeper are also moved to the files files sp_instr.cc/sp_instr.h.
Additionally,
* all occurrences of macroses NULL, FALSE, TRUE are replaced
with the corresponding C++ keywords nullptr, false, true.
* the keyword 'override' is added in and the keyword 'virtual' is removed
from signatures of every virtual method implemented in classes derived
from the base class sp_instr.
* the keyword 'final' is added into declaration of the class sp_lex_keeper
since this class shouldn't have a derived class by design.
* the function cmp_rqp_locations is made static since it is not called
outside the file sp_instr.cc.
* the function subst_spvars() is moved into the file sp_instr.cc since this
function used only by the method sp_instr_stmt::execute
- Moving the code from a public function trim_whitespaces()
to the class Lex_cstring as methods. This code may
be useful in other contexts, and also this code becomes
visible inside sql_class.h
- Adding a helper method THD::strmake_lex_cstring_trim_whitespaces()
- Unifying the way how CREATE PROCEDURE/CREATE FUNCTION and
CREATE PACKAGE/CREATE PACKAGE BODY work:
a) Now CREATE PACKAGE/CREATE PACKAGE BODY also calls
Lex->sphead->set_body_start() to remember the cpp body start inside
an sp_head member.
b) adding a "const char *cpp_body_end" parameter to
sp_head::set_stmt_end().
These changes made it possible to reuse sp_head::set_stmt_end() inside
LEX::create_package_finalize() and remove the duplucate code.
- Renaming sp_head::m_body_begin to m_cpp_body_begin and adding a comment
to make it clear that this member is used only during parsing, and
points to a fragment inside the cpp buffer.
- Changed sp_head::set_body_start() and sp_head::set_stmt_end()
to skip the calls related to "body_utf8" in cases when m_parent is not NULL.
A non-NULL m_parent means that we're inside a package routine.
"body_utf8" in such case belongs not to the current sphead itself,
but to parent (the package) sphead.
So an sphead instance of a package routine should neither initialize,
nor finalize, nor change in any other ways the "body_utf8" related
members of Lex_input_stream, and should not take over or copy "body_utf8"
data from Lex_input_stream to "this".
The parser works as follows:
The rule expr_lex returns a pointer to a newly created sp_expr_lex
instance which is not linked to any MariaDB structures yet - it is
pointed only from a Bison stack variable. The sp_expr_lex instance
gets linked to other structures (such as sp_instr_jump_if_not) later,
after scanning some following grammar.
Problem before the fix:
If a parse error happened immediately after expr_lex (before it got linked),
the created sp_expr_lex value got lost causing a memory leak.
Fix:
- Using Bison's "destructor" directive to free the results of expr_lex
on parse/oom errors.
- Moving the call for LEX::cleanup_lex_after_parse_error() from
MYSQL_YYABORT and yyerror inside parse_sql().
This is needed because Bison calls destructors after yyerror(),
while it's important to delete the sp_expr_lex instance before
LEX::cleanup_lex_after_parse_error().
The latter frees the memory root containing the sp_expr_lex instance.
After this change the code block are executed in the following order:
- yyerror() -- now only raises the error to DA (no cleanup done any more)
- %destructor { delete $$; } <expr_lex> -- destructs the sp_expr_lex instance
- LEX::cleanup_lex_after_parse_error() -- frees the memory root containing
the sp_expr_lex instance
- Removing the "delete sublex" related code from restore_lex():
- restore_lex() is called in most cases on success, when delete is not needed.
- There is one place when restore_lex() is called on error:
In sp_create_assignment_instr(). But in this case LEX::sp_lex_in_use
is true anyway.
The patch adds a new DBUG_ASSERT(lex->sp_lex_in_use) to guard this.
Allow queries of multiple SELECTs combined together with
UNIONs/EXCEPTs/INTERSECTs to be pushed down to foreign engines.
If the foreign engine provides an interface method "create_unit"
and the UNIT is a top-level unit of the SQL query then the server
tries to push the whole SELECT_LEX_UNIT down to the engine for execution.
The engine should perform necessary checks and if they succeed,
execute the query. If the engine is unable to execute the whole unit,
then another attempt is made to push down SELECTs composing the unit
separately using the "create_select" interface method. In this case
the results of separate SELECTs are combined at the server side
thus composing the final result
This bug could cause a crash of the server when processing a query with
ROWNUM() if it used in its FROM list a reference to a mergeable view
defined as SELECT over more than one table that contained ORDER BY clause.
When a mergeable view with ORDER BY clause and without LIMIT clause is used
in the FROM list of a query that does not have ORDER BY clause the ORDER BY
clause of the view is moved to the query. The code that performed this
transformation forgot to delete the moved ORDER BY list from the view.
If a query contains ROWNUM() and uses a mergeable multi-table view with
ORDER BY then according to the current code of TABLE_LIST::init_derived()
the view has to be forcibly materialized. As the query and the view shared
the same items in its ORDER BY lists they could not be properly resolved
either in the query or in the view. This led to a crash of the server.
This patch has returned back the original signature of LEX::can_not_use_merged()
to comply with 10.4 code of the condition that checks whether a megeable
view has to be forcibly materialized.
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.
