create templates
thd->alloc<X>(n) to use instead of (X*)thd->alloc(sizeof(X)*n)
and the same for thd->calloc(). By the default the type is char,
so old usage of thd->alloc(size) works too.
Adding support for the ROW data type in the stored function RETURNS clause:
- explicit ROW(..members...) for both sql_mode=DEFAULT and sql_mode=ORACLE
CREATE FUNCTION f1() RETURNS ROW(a INT, b VARCHAR(32)) ...
- anchored "ROW TYPE OF [db1.]table1" declarations for sql_mode=DEFAULT
CREATE FUNCTION f1() RETURNS ROW TYPE OF test.t1 ...
- anchored "[db1.]table1%ROWTYPE" declarations for sql_mode=ORACLE
CREATE FUNCTION f1() RETURN test.t1%ROWTYPE ...
Adding support for anchored scalar data types in RETURNS clause:
- "TYPE OF [db1.]table1.column1" for sql_mode=DEFAULT
CREATE FUNCTION f1() RETURNS TYPE OF test.t1.column1;
- "[db1.]table1.column1" for sql_mode=ORACLE
CREATE FUNCTION f1() RETURN test.t1.column1%TYPE;
Details:
- Adding a new sql_mode_t parameter to
sp_head::create()
sp_head::sp_head()
sp_package::create()
sp_package::sp_package()
to guarantee early initialization of sp_head::m_sql_mode.
Before this change, this member was not initialized at all during
CREATE FUNCTION/PROCEDURE/PACKAGE statements, and was not used.
Now it needs to be initialized to write properly the
mysql.proc.returns column, according to the create time sql_mode.
- Code refactoring to make the things simpler and functions smaller:
* Adding a new method
Field_row::row_create_fields(THD *thd, List<Spvar_definition> *list)
to make a Virtual_tmp_table with Fields for ROW members
from an explicit definition.
* Adding a new method
Field_row::row_create_fields(THD *thd, const Spvar_definition &def)
to make a Virtual_tmp_table with Fields for ROW members
from an explicit or a table anchored definition.
* Adding a new method
Item_args::add_array_of_item_field(THD *thd, const Virtual_tmp_table &vtable)
to create and array of Item_field corresponding to all Field instances
in a Virtual_tmp_table
* Removing Item_field_row::row_create_items(). It was decomposed
into the new methods described above.
* Moving the code from the loop body in sp_rcontext::init_var_items()
into a separate method Spvar_definition::make_item_field_row(),
to make the code clearer (smaller functions).
make_item_field_row() itself uses the new methods described above.
- Changing the data type of sp_head::m_return_field_def
from Column_definition to Spvar_definition.
So now it supports not only SQL column field types,
but also explicit ROW and anchored ROW data types,
as well as anchored column types.
- Adding a new Column_definition parameter to sp_head::create_result_field().
Before this patch, create_result_field() took the definition only
from m_return_field_def. Now it's also called with a local Column_definition
variable which contains the explicit definition resolved from an
anchored defition.
- Modifying sql_yacc.yy to support the new grammar.
Adding new helper methods:
* sf_return_fill_definition_row()
* sf_return_fill_definition_rowtype_of()
* sf_return_fill_definition_type_of()
- Fixing tests in:
* Virtual_tmp_table::setup_field_pointers() in sql_select.cc
* Send_field::normalize() in field.h
* store_column_type()
to prevent calling Type_handler_row::field_type(),
which is implemented a DBUG_ASSERT(0).
Before this patch the affected methods and functions were called only
for scalar data types. Now ROW is also possible.
- Adding a new virtual method Field::cols()
- Overriding methods:
Item_func_sp::cols()
Item_func_sp::element_index()
Item_func_sp::check_cols()
Item_func_sp::bring_value()
to support the ROW data type.
- Extending the rule sp_return_type to support
* explicit ROW and anchored ROW data types
* anchored scalar data types
- Overriding Field_row::sql_type() to print
the data type of an explicit ROW.
This patch also fixes:
MDEV-33050 Build-in schemas like oracle_schema are accent insensitive
MDEV-33084 LASTVAL(t1) and LASTVAL(T1) do not work well with lower-case-table-names=0
MDEV-33085 Tables T1 and t1 do not work well with ENGINE=CSV and lower-case-table-names=0
MDEV-33086 SHOW OPEN TABLES IN DB1 -- is case insensitive with lower-case-table-names=0
MDEV-33088 Cannot create triggers in the database `MYSQL`
MDEV-33103 LOCK TABLE t1 AS t2 -- alias is not case sensitive with lower-case-table-names=0
MDEV-33109 DROP DATABASE MYSQL -- does not drop SP with lower-case-table-names=0
MDEV-33110 HANDLER commands are case insensitive with lower-case-table-names=0
MDEV-33119 User is case insensitive in INFORMATION_SCHEMA.VIEWS
MDEV-33120 System log table names are case insensitive with lower-cast-table-names=0
- Removing the virtual function strnncoll() from MY_COLLATION_HANDLER
- Adding a wrapper function CHARSET_INFO::streq(), to compare
two strings for equality. For now it calls strnncoll() internally.
In the future it will turn into a virtual function.
- Adding new accent sensitive case insensitive collations:
- utf8mb4_general1400_as_ci
- utf8mb3_general1400_as_ci
They implement accent sensitive case insensitive comparison.
The weight of a character is equal to the code point of its
upper case variant. These collations use Unicode-14.0.0 casefolding data.
The result of
my_charset_utf8mb3_general1400_as_ci.strcoll()
is very close to the former
my_charset_utf8mb3_general_ci.strcasecmp()
There is only a difference in a couple dozen rare characters, because:
- the switch from "tolower" to "toupper" comparison, to make
utf8mb3_general1400_as_ci closer to utf8mb3_general_ci
- the switch from Unicode-3.0.0 to Unicode-14.0.0
This difference should be tolarable. See the list of affected
characters in the MDEV description.
Note, utf8mb4_general1400_as_ci correctly handles non-BMP characters!
Unlike utf8mb4_general_ci, it does not treat all BMP characters
as equal.
- Adding classes representing names of the file based database objects:
Lex_ident_db
Lex_ident_table
Lex_ident_trigger
Their comparison collation depends on the underlying
file system case sensitivity and on --lower-case-table-names
and can be either my_charset_bin or my_charset_utf8mb3_general1400_as_ci.
- Adding classes representing names of other database objects,
whose names have case insensitive comparison style,
using my_charset_utf8mb3_general1400_as_ci:
Lex_ident_column
Lex_ident_sys_var
Lex_ident_user_var
Lex_ident_sp_var
Lex_ident_ps
Lex_ident_i_s_table
Lex_ident_window
Lex_ident_func
Lex_ident_partition
Lex_ident_with_element
Lex_ident_rpl_filter
Lex_ident_master_info
Lex_ident_host
Lex_ident_locale
Lex_ident_plugin
Lex_ident_engine
Lex_ident_server
Lex_ident_savepoint
Lex_ident_charset
engine_option_value::Name
- All the mentioned Lex_ident_xxx classes implement a method streq():
if (ident1.streq(ident2))
do_equal();
This method works as a wrapper for CHARSET_INFO::streq().
- Changing a lot of "LEX_CSTRING name" to "Lex_ident_xxx name"
in class members and in function/method parameters.
- Replacing all calls like
system_charset_info->coll->strcasecmp(ident1, ident2)
to
ident1.streq(ident2)
- Taking advantage of the c++11 user defined literal operator
for LEX_CSTRING (see m_strings.h) and Lex_ident_xxx (see lex_ident.h)
data types. Use example:
const Lex_ident_column primary_key_name= "PRIMARY"_Lex_ident_column;
is now a shorter version of:
const Lex_ident_column primary_key_name=
Lex_ident_column({STRING_WITH_LEN("PRIMARY")});
and to related methods and their parameters:
- The return value of Spvar_definition::m_column_type_ref()
- The parameter of Spvar_definition::set_column_type_ref()
- The method Qualified_column_ident::resolve_type_ref()
- The parameter of LEX::sp_variable_declarations_column_type_finalize()
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.
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
use existing Warning_info::m_current_row_for_warning instead
of a newly introduced counter.
But use m_current_row_for_warning to count rows also in the parser
and during prepare.
Extended the parser for GET DIAGNOSTICS to use ERROR_INDEX to get
warning/error index.
Error information is stored in Sql_condition. So it can be used to
store the index of warning/error too. THD::current_insert_index keeps a
track of count for each row that is processed or going to be inserted in the
table (or first row in case of prepare phase). When an error occurs,
first we need to fetch corrected error index (using correct_error_index())
for an error number. This is needed because in prepare phase, the error
may not be because of rows/values. In such case, correct value of
error_index should be 0. Once correct value if fetched, assign it to
Sql_condition::error_index when the object is created during error/warning.
This error_index variable is returned when ERROR_INDEX is used in
GET DIAGNOSTICS.
Changing the way how a cursor is opened to fetch its structure only,
e.g. for a cursor FOR loop record variable.
The old methods with setting thd->lex->limit_rows_examined to an Item_uint(0)
was not reliable and could push these messages into diagnostics area:
The query examined at least 1 rows, which exceeds LIMIT ROWS EXAMINED (0)
The new method should be more reliable, as it completely prevents the call
of do_select() in JOIN::exec_inner() during the cursor structure discovery,
so the execution of the cursor SELECT query returns immediately after the
preparation step (when the result row structure becomes known),
without even entering the code that fetches the result rows.
Problem:
push_handler() created sp_handler_entry instances on THD::main_mem_root,
which is freed only after the SP instructions execution.
So in case of a CONTINUE HANDLER inside a loop (e.g. WHILE) this approach
leaked thread memory on every loop iteration.
Changes:
- Removing sp_handler_entry declaration, it's not really needed.
- Fixing the data type of sp_rcontext::m_handlers from
Dynamic_array<sp_handler_entry*> to Dynamic_array<sp_instr_hpush_jump*>
- Fixing sp_rcontext::push_handler() to push the pointer to
an sp_instr_hpush_jump instance to the handler stack.
This instance contains everything we need.
There is no a need to allocate anything else.
Problem:
push_cursor() created sp_cursor instances on THD::main_mem_root,
which is freed only after the SP instructions loop.
Changes:
- Moving sp_cursor declaration from sp_rcontext.h to sql_class.h
- Deriving sp_instr_cpush from sp_cursor. So now sp_cursor is created
only once (at the SP parse time) and then reused on all loop iterations
- Adding a new method reset() into sp_cursor (and its parent classes)
to reset an sp_cursor instance before reuse.
- Moving former sp_cursor members m_fetch_count, m_row_count, m_found
into a separate class sp_cursor_statistics. This helps to reuse
the code in sp_cursor constructors, and in sp_cursor::reset()
- Adding a helper method sp_rcontext::pop_cursor().
- Adding "THD*" parameter to so_rcontext::pop_cursors() and pop_all_cursors()
- Removing "new" and "delete" from sp_rcontext::push_cursor() and
sp_rconext::pop_cursor().
- Fixing sp_cursor not to derive from Sql_alloc, as it's now allocated
only as a part of sp_instr_cpush (and not allocated separately).
- Moving lex_keeper->disable_query_cache() from sp_cursor::sp_cursor()
to sp_instr_cpush::execute().
- Adding tests
Problem:
The problem was most likely introduced by a fix for MDEV-11597
(commit 5f0c31f928) which removed
the assignment "killed= KILL_BAD_DATA" from THD::raise_condition().
Before MDEV-11597, sp_head::execute() tested thd->killed after
looping through the SP instructions and exited with an error
if thd->killed is set. After MDEV-11597, sp_head::execute()
stopped to notice errors and set the OK status on top of the
error status, which crashed on assert.
Fix:
Making sp_cursor::fetch() return -1 if server_side_cursor->fetch(1)
left an error in the diagnostics area. This makes the statement
"err_status= i->execute(thd, &ip)" in sp_head::execute() set the
error code and correctly break the SP instruction loop and
return on error without setting the OK status.
- Using array_elements() instead of a constant to iterate through an array
- Adding some comments
- Adding new-line function comments
- Using STRING_WITH_LEN instead of C_STRING_WITH_LEN
SYSTEM_INVISIBLE or COMPLETELY_INVISIBLE
This commit does multiple things to solve this mdev
1st add field into the parameter of check_column_grant_in_table_ref, so that
we can find out field invisibility.
2nd If field->invisible >= INVISIBLE_SYSTEM skip access check and simple
grant access.
- CREATE PACKAGE [BODY] statements are now
entirely written to mysql.proc with type='PACKAGE' and type='PACKAGE BODY'.
- CREATE PACKAGE BODY now supports IF NOT EXISTS
- DROP PACKAGE BODY now supports IF EXISTS
- CREATE OR REPLACE PACKAGE [BODY] is now supported
- CREATE PACKAGE [BODY] now support the DEFINER clause:
CREATE DEFINER user@host PACKAGE pkg ... END;
CREATE DEFINER user@host PACKAGE BODY pkg ... END;
- CREATE PACKAGE [BODY] now supports SQL SECURITY and COMMENT clauses, e.g.:
CREATE PACKAGE p1 SQL SECURITY INVOKER COMMENT "comment" AS ... END;
- Package routines are now created from the package CREATE PACKAGE BODY
statement and don't produce individual records in mysql.proc.
- CREATE PACKAGE BODY now supports package-wide variables.
Package variables can be read and set inside package routines.
Package variables are stored in a separate sp_rcontext,
which is cached in THD on the first packate routine call.
- CREATE PACKAGE BODY now supports the initialization section.
- All public routines (i.e. declared in CREATE PACKAGE)
must have implementations in CREATE PACKAGE BODY
- Only public package routines are available outside of the package
- {CREATE|DROP} PACKAGE [BODY] now respects CREATE ROUTINE and ALTER ROUTINE
privileges
- "GRANT EXECUTE ON PACKAGE BODY pkg" is now supported
- SHOW CREATE PACKAGE [BODY] is now supported
- SHOW PACKAGE [BODY] STATUS is now supported
- CREATE and DROP for PACKAGE [BODY] now works for non-current databases
- mysqldump now supports packages
- "SHOW {PROCEDURE|FUNCTION) CODE pkg.routine" now works for package routines
- "SHOW PACKAGE BODY CODE pkg" now works (the package initialization section)
- A new package body level MDL was added
- Recursive calls for package procedures are now possible
- Routine forward declarations in CREATE PACKATE BODY are now supported.
- Package body variables now work as SP OUT parameters
- Package body variables now work as SELECT INTO targets
- Package body variables now support ROW, %ROWTYPE, %TYPE
Handle string length as size_t, consistently (almost always:))
Change function prototypes to accept size_t, where in the past
ulong or uint were used. change local/member variables to size_t
when appropriate.
This fix excludes rocksdb, spider,spider, sphinx and connect for now.
- Changing sp_rcontext::m_var_items from list of Item to list of Item_field
- Renaming sp_rcontext::get_item() to get_variable() and changing
its return type from Item* to Item_field *
- Adding sp_rcontext::get_parameter() and sp_rcontext::set_parameter(),
wrappers for get_variable() and set_variable() with extra DBUG_ASSERT.
Using new methods instead of get_variable()/set_variable() in
relevant places.
After MDEV-14212, the Virtual_tmp_table instance that stores a ROW
variable elements is accessible from the underlying Field_row
(rather than Item_field_row).
This patch makes some further changes by moving the code from
sp_instr_xxx, sp_rcontext, Item_xxx to Virtual_tmp_table and Field_xxx.
The data type specific code (scalar vs ROW) now resides in
a new virtual method Field_xxx::sp_prepare_and_store_item().
The the code in sp_rcontext::set_variable() and sp_eval_expr()
is now symmetric for scalar and ROW values.
The code in sp_rcontext::set_variable_row_field(), sp_rcontext::set_variable_row_field(), sp_rcontext::set_variable_row()
is now symmetric for ROW elements (i.e. scalar and ROW elements inside a ROW).
Rationale:
Prepare the code to implement these tasks soon easier:
- MDEV-12252 ROW data type for stored function return values
- MDEV-12307 ROW data type for built-in function return values
- MDEV-6121 Data type: Array
- MDEV-10593 sql_mode=ORACLE: TYPE .. AS OBJECT: basic functionality
- ROW with ROW fields (no MDEV yet)
Details:
1. Moving the code in sp_eval_expr() responsible to backup/restore
thd->count_cuted_fields, thd->abort_on_warning,
thd->transaction.stmt.modified_non_trans_table
into a new helper class Sp_eval_expr_state, to reuse it easier.
Fixing sp_eval_expr() to use this new class.
2. Moving sp_eval_expr() and sp_prepare_func_item() from public functions
to methods in THD, so they can be reused in *.cc files easier without
a need to include "sp_head.h".
Splitting sp_prepare_func_item() into two parts.
Adding a new function sp_fix_func_item(), which fixes
the underlying items, but does not do check_cols() for them.
Reusing sp_fix_func_item() in Field_row::sp_prepare_and_store_item().
3. Moving the code to find ROW fields by name from Item to Virtual_tmp_table
Moving the code searching for ROW fields by their names
from Item_field_row::element_index_by_name() to a new method
Item_field_row to Virtual_tmp_table::sp_find_field_by_name().
Adding wrapper methods sp_rcontext::find_row_field_by_name() and
find_row_field_by_name_or_error(), to search for a ROW variable
fields by the variable offset and its field name.
Changing Item_splocal_row_field_by_name::fix_fields() to do
use sp_rcontext::find_row_field_by_name_or_error().
Removing virtual Item::element_index_by_name().
4. Splitting sp_rcontext::set_variable()
Adding a new virtual method Field::sp_prepare_and_store_item().
Spliting the two branches of the code in sp_rcontext::set_variable()
into two virtual implementations of Field::sp_prepare_and_store_item(),
(for Field and for Field_row).
Moving the former part of sp_rcontext::set_variable() with the loop
doing set_null() for all ROW fields into a new method
Virtual_tmp_table::set_all_fields_to_null() and using it in
Field_row::sp_prepare_and_store_item().
Moving the former part of sp_rcontext::set_variable() with the loop
doing set_variable_row_field() into a new method
Virtual_tmp_table::set_all_fields_from_item() and using it in
Field_row::sp_prepare_and_store_item().
The loop in the new method now uses sp_prepare_and_store_item()
instead of set_variable_row_field(), because saving/restoring
THD flags is now done on the upper level. No needs to save/restore
on every iteration.
5. Fixing sp_eval_expr() to simply do two things:
- backup/restore THD flags
- call result_field->sp_prepare_and_store_item()
So now sp_eval_expr() can be used for both scalar and ROW variables.
Reusing it in sp_rcontext::set_variable*().
6. Moving the loop in sp_rcontext::set_variable_row() into a
new method Virtual_tmp_table::sp_set_all_fields_from_item_list().
Changing the loop body to call field->sp_prepare_and_store_item()
instead of doing set_variable_row_field(). This removes
saving/restoring of the THD flags from every interation.
Instead, adding the code to save/restore the flags around
the entire loop in set_variable_row(), using Sp_eval_expr_state.
So now saving/restoring is done only once for the entire ROW
(a slight performance improvement).
7. Removing the code in sp_instr_set::exec_core() that sets
a variable to NULL if the value evaluation failed.
sp_rcontext::set_variable() now makes sure to reset
the variable properly by effectively calling sp_eval_expr(),
which calls virtual Field::sp_prepare_and_store_item().
Removing the similar code from sp_instr_set_row_field::exec_core()
and sp_instr_set_row_field_by_name::exec_core().
Removing the method sp_rcontext::set_variable_row_field_to_null(),
as it's not used any more.
8. Removing the call for sp_prepare_func_item() from
sp_rcontext::set_variable_row_field(), as it was duplicate:
it was done inside sp_eval_expr(). Now it's done inside
virtual Field::sp_prepare_and_store_item().
9. Moving the code from sp_instr_set_row_field_by_name::exec_core()
into sp_rcontext::set_variable_row_field_by_name(), for symmetry
with other sp_instr_set*::exec_core()/sp_rcontext::set_variable*() pairs.
Now sp_instr_set_row_field_by_name::exec_core() calls
sp_rcontext::set_variable_row_field_by_name().
10. Misc:
- Adding a helper private method sp_rcontext::virtual_tmp_table_for_row(),
reusing it in a new sp_rcontext methods.
- Removing Item_field_row::get_row_field(), as it's not used any more.
- Removing the "Item *result_item" from sp_eval_expr(),
as it's not needed any more.
current_select may point to data from old parser states
when calling a stored procedure with CALL
The failure happens in Item::Item when testing if we are
in having.
Fixed by explicitely reseting current_select in do_execute_sp()
and in sp_rcontext::create(). The later is also needed for
stored functions().
This commit implements aggregate stored functions. The basic idea behind
the feature is:
* Implement a special instruction FETCH GROUP NEXT ROW that will pause
the execution of the stored function. When the instruction is reached,
execution of the initial query resumes "as if" the function returned.
This gives the server the opportunity to advance to the next row in the
result set.
* Stored aggregates behave like regular aggregate functions. The
implementation of thus resides in the class Item_sum_sp. Because it is
an aggregate function, for each new row in the group, the
Item_sum_sp::add() method will be called. This is when execution resumes
and the function does another iteration to "add" one extra element to
the final result.
* When the end of group is reached, val_xxx() method will be called for
the item. This case is handled by another execute step for the stored
function, only with a special flag to force a call to the return
handler. See Item_sum_sp::execute() for details.
To allow this pause and resume semantic, we must preserve the function
context across executions. This is stored in Item_sp::sp_query_arena only for
aggregate stored functions, but has no impact for regular functions.
We also enforce aggregate functions to include the "FETCH GROUP NEXT ROW"
instruction.
Signed-off-by: Vicențiu Ciorbaru <vicentiu@mariadb.org>
- Renaming sp_rcontext::sp to sp_rcontext:m_sp for consistency
with other sp_rcontext_members, and for consistency with the
same purpose member Item_sp_variable::m_sp.
- Passing a "const sp_head*" pointer to sp_rcontext::sp_rcontext()
and to sp_rcontext::create().
Initializing sp_rcontext::m_sp right in the constructor
instead of having a separate initialization after "new sp_rcontext"
or sp_rcontext::create().
- Adding the "const" qualifier to sp_rcontext::m_sp and Item_sp_variable::m_sp
Changing datatypes for:
- Item_spvar_args::m_table
- sp_rcontext::m_var_table
- return value of create_virtual_tmp_table()
from TABLE* to Virtual_tmp_table*
Advantages:
- Stricter data type control
- Removing the duplicate code (a loop with free_blobs)
from destructors ~sp_rcontext() and ~Item_spvar_args(),
using "delete m_(var_)table" in both instead.
- Using Virtual_tmp_table::delete makes the code call Field::delete,
which calls TRASH() for the freed fields,
which is good for valgrind test runs.
