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mariadb/sql/sql_union.cc
Igor Babaev b14e2b044b This first patch prepared for the task MDEV-13369: 
"Optimization for equi-joins of derived tables with GROUP BY"
should be considered rather as a 'proof of concept'.

The task itself is targeted at an optimization that employs re-writing
equi-joins with grouping derived tables / views into lateral
derived tables. Here's an example of such transformation:
  select t1.a,t.max,t.min
  from t1 [left] join
       (select a, max(t2.b) max, min(t2.b) min from t2
       group by t2.a) as t
       on t1.a=t.a;
=>
  select t1.a,tl.max,tl.min
  from t1 [left] join
       lateral (select a, max(t2.b) max, min(t2.b) min from t2
                where  t1.a=t2.a) as t
       on 1=1;
The transformation pushes the equi-join condition t1.a=t.a into the
derived table making it dependent on table t1. It means that for
every row from t1 a new derived table must be filled out. However
the size of any of these derived tables is just a fraction of the
original derived table t. One could say that transformation 'splits'
the rows used for the GROUP BY operation into separate groups
performing aggregation for a group only in the case when there is
a match for the current row of t1.
Apparently the transformation may produce a query with a better
performance only in the case when
 - the GROUP BY list refers only to fields returned by the derived table
 - there is an index I on one of the tables T used in FROM list of
   the specification of the derived table whose prefix covers the
   the fields from the proper beginning of the GROUP BY list or
   fields that are equal to those fields.
Whether the result of the re-writing can be executed faster depends
on many factors:
  - the size of the original derived table
  - the size of the table T
  - whether the index I is clustering for table T
  - whether the index I fully covers the GROUP BY list.

This patch only tries to improve the chosen execution plan using
this transformation. It tries to do it only when the chosen
plan reaches the derived table by a key whose prefix covers
all the fields of the derived table produced by the fields of
the table T from the GROUP BY list.
The code of the patch does not evaluates the cost of the improved
plan. If certain conditions are met the transformation is applied.
2017-08-10 14:26:29 -07:00

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/* Copyright (c) 2000, 2014, Oracle and/or its affiliates.
Copyright (c) 2010, 2014, SkySQL Ab.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
/*
UNION of select's
UNION's were introduced by Monty and Sinisa <sinisa@mysql.com>
*/
#include <my_global.h>
#include "sql_priv.h"
#include "unireg.h"
#include "sql_union.h"
#include "sql_select.h"
#include "sql_cursor.h"
#include "sql_base.h" // fill_record
#include "filesort.h" // filesort_free_buffers
#include "sql_view.h"
#include "sql_cte.h"
bool mysql_union(THD *thd, LEX *lex, select_result *result,
SELECT_LEX_UNIT *unit, ulong setup_tables_done_option)
{
DBUG_ENTER("mysql_union");
bool res;
if (!(res= unit->prepare(thd, result, SELECT_NO_UNLOCK |
setup_tables_done_option)))
res= unit->exec();
res|= unit->cleanup();
DBUG_RETURN(res);
}
/***************************************************************************
** store records in temporary table for UNION
***************************************************************************/
int select_unit::prepare(List<Item> &list, SELECT_LEX_UNIT *u)
{
unit= u;
return 0;
}
/**
This called by SELECT_LEX_UNIT::exec when select changed
*/
void select_unit::change_select()
{
uint current_select_number= thd->lex->current_select->select_number;
DBUG_ENTER("select_unit::change_select");
DBUG_PRINT("enter", ("select in unit change: %u -> %u",
curr_sel, current_select_number));
DBUG_ASSERT(curr_sel != current_select_number);
curr_sel= current_select_number;
/* New SELECT processing starts */
DBUG_ASSERT(table->file->inited == 0);
switch (thd->lex->current_select->linkage)
{
case INTERSECT_TYPE:
intersect_mark->value= prev_step= curr_step;
curr_step= current_select_number;
case EXCEPT_TYPE:
step= thd->lex->current_select->linkage;
break;
default:
step= UNION_TYPE;
break;
}
DBUG_VOID_RETURN;
}
/**
Fill temporary tables for UNION/EXCEPT/INTERSECT
@Note
UNION:
just add records to the table (with 'counter' field first if INTERSECT
present in the sequence).
EXCEPT:
looks for the record in the table (with 'counter' field first if
INTERSECT present in the sequence) and delete it if found
INTESECT:
looks for the same record with 'counter' field of previous operation,
put as a 'counter' number of the current SELECT.
We scan the table and remove all records which marked with not last
'counter' after processing all records in send_eof and only if it last
SELECT of sequence of INTERSECTS.
@param values List of record items to process.
@retval 0 - OK
@retval -1 - duplicate
@retval 1 - error
*/
int select_unit::send_data(List<Item> &values)
{
int rc;
int not_reported_error= 0;
if (unit->offset_limit_cnt)
{ // using limit offset,count
unit->offset_limit_cnt--;
return 0;
}
if (thd->killed == ABORT_QUERY)
return 0;
if (table->no_rows_with_nulls)
table->null_catch_flags= CHECK_ROW_FOR_NULLS_TO_REJECT;
if (intersect_mark)
{
fill_record(thd, table, table->field + 1, values, TRUE, FALSE);
table->field[0]->store((ulonglong) curr_step, 1);
}
else
fill_record(thd, table, table->field, values, TRUE, FALSE);
if (thd->is_error())
{
rc= 1;
goto end;
}
if (table->no_rows_with_nulls)
{
table->null_catch_flags&= ~CHECK_ROW_FOR_NULLS_TO_REJECT;
if (table->null_catch_flags)
{
rc= 0;
goto end;
}
}
// select_unit::change_select() change step & Co correctly for each SELECT
switch (step)
{
case UNION_TYPE:
{
if ((write_err= table->file->ha_write_tmp_row(table->record[0])))
{
if (write_err == HA_ERR_FOUND_DUPP_KEY)
{
/*
Inform upper level that we found a duplicate key, that should not
be counted as part of limit
*/
rc= -1;
goto end;
}
bool is_duplicate= FALSE;
/* create_internal_tmp_table_from_heap will generate error if needed */
if (table->file->is_fatal_error(write_err, HA_CHECK_DUP) &&
create_internal_tmp_table_from_heap(thd, table,
tmp_table_param.start_recinfo,
&tmp_table_param.recinfo,
write_err, 1, &is_duplicate))
{
rc= 1;
goto end;
}
if (is_duplicate)
{
rc= -1;
goto end;
}
}
break;
}
case EXCEPT_TYPE:
{
int find_res;
/*
The temporary table uses very first index or constrain for
checking unique constrain.
*/
if (!(find_res= table->file->find_unique_row(table->record[0], 0)))
{
DBUG_ASSERT(!table->triggers);
table->status|= STATUS_DELETED;
not_reported_error= table->file->ha_delete_tmp_row(table->record[0]);
rc= MY_TEST(not_reported_error);
goto end;
}
else
{
if ((rc= not_reported_error= (find_res != 1)))
goto end;
}
break;
}
case INTERSECT_TYPE:
{
int find_res;
/*
The temporary table uses very first index or constrain for
checking unique constrain.
*/
if (!(find_res= table->file->find_unique_row(table->record[0], 0)))
{
DBUG_ASSERT(!table->triggers);
if (table->field[0]->val_int() != prev_step)
{
rc= 0;
goto end;
}
store_record(table, record[1]);
table->field[0]->store(curr_step, 0);
not_reported_error= table->file->ha_update_tmp_row(table->record[1],
table->record[0]);
rc= MY_TEST(not_reported_error);
DBUG_ASSERT(rc != HA_ERR_RECORD_IS_THE_SAME);
goto end;
}
else
{
if ((rc= not_reported_error= (find_res != 1)))
goto end;
}
break;
}
default:
DBUG_ASSERT(0);
}
rc= 0;
end:
if (not_reported_error)
{
DBUG_ASSERT(rc);
table->file->print_error(not_reported_error, MYF(0));
}
return rc;
}
bool select_unit::send_eof()
{
if (step != INTERSECT_TYPE ||
(thd->lex->current_select->next_select() &&
thd->lex->current_select->next_select()->linkage == INTERSECT_TYPE))
{
/*
it is not INTESECT or next SELECT in the sequence is INTERSECT so no
need filtering (the last INTERSECT in this sequence of intersects will
filter).
*/
return 0;
}
/*
It is last select in the sequence of INTERSECTs so we should filter out
all records except marked with actual counter.
TODO: as optimization for simple case this could be moved to
'fake_select' WHERE condition
*/
handler *file= table->file;
int error;
if (file->ha_rnd_init_with_error(1))
return 1;
do
{
error= file->ha_rnd_next(table->record[0]);
if (error)
{
if (error == HA_ERR_END_OF_FILE)
{
error= 0;
break;
}
if (unlikely(error == HA_ERR_RECORD_DELETED))
{
error= 0;
continue;
}
break;
}
if (table->field[0]->val_int() != curr_step)
error= file->ha_delete_tmp_row(table->record[0]);
} while (!error);
file->ha_rnd_end();
if (error)
table->file->print_error(error, MYF(0));
return(MY_TEST(error));
}
int select_union_recursive::send_data(List<Item> &values)
{
int rc= select_unit::send_data(values);
if (write_err != HA_ERR_FOUND_DUPP_KEY &&
write_err != HA_ERR_FOUND_DUPP_UNIQUE)
{
int err;
if ((err= incr_table->file->ha_write_tmp_row(table->record[0])))
{
bool is_duplicate;
rc= create_internal_tmp_table_from_heap(thd, incr_table,
tmp_table_param.start_recinfo,
&tmp_table_param.recinfo,
err, 1, &is_duplicate);
}
}
return rc;
}
bool select_unit::flush()
{
int error;
if ((error=table->file->extra(HA_EXTRA_NO_CACHE)))
{
table->file->print_error(error, MYF(0));
return 1;
}
return 0;
}
/*
Create a temporary table to store the result of select_union.
SYNOPSIS
select_unit::create_result_table()
thd thread handle
column_types a list of items used to define columns of the
temporary table
is_union_distinct if set, the temporary table will eliminate
duplicates on insert
options create options
table_alias name of the temporary table
bit_fields_as_long convert bit fields to ulonglong
create_table whether to physically create result table
keep_row_order keep rows in order as they were inserted
hidden number of hidden fields (for INTERSECT)
DESCRIPTION
Create a temporary table that is used to store the result of a UNION,
derived table, or a materialized cursor.
RETURN VALUE
0 The table has been created successfully.
1 create_tmp_table failed.
*/
bool
select_unit::create_result_table(THD *thd_arg, List<Item> *column_types,
bool is_union_distinct, ulonglong options,
const char *alias,
bool bit_fields_as_long, bool create_table,
bool keep_row_order,
uint hidden)
{
DBUG_ASSERT(table == 0);
tmp_table_param.init();
tmp_table_param.field_count= column_types->elements;
tmp_table_param.bit_fields_as_long= bit_fields_as_long;
tmp_table_param.hidden_field_count= hidden;
if (! (table= create_tmp_table(thd_arg, &tmp_table_param, *column_types,
(ORDER*) 0, is_union_distinct, 1,
options, HA_POS_ERROR, alias,
!create_table, keep_row_order)))
return TRUE;
table->keys_in_use_for_query.clear_all();
for (uint i=0; i < table->s->fields; i++)
table->field[i]->flags &= ~PART_KEY_FLAG;
if (create_table)
{
table->file->extra(HA_EXTRA_WRITE_CACHE);
table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
}
return FALSE;
}
bool
select_union_recursive::create_result_table(THD *thd_arg,
List<Item> *column_types,
bool is_union_distinct,
ulonglong options,
const char *alias,
bool bit_fields_as_long,
bool create_table,
bool keep_row_order,
uint hidden)
{
if (select_unit::create_result_table(thd_arg, column_types,
is_union_distinct, options,
"", bit_fields_as_long,
create_table, keep_row_order,
hidden))
return true;
if (! (incr_table= create_tmp_table(thd_arg, &tmp_table_param, *column_types,
(ORDER*) 0, false, 1,
options, HA_POS_ERROR, "",
!create_table, keep_row_order)))
return true;
incr_table->keys_in_use_for_query.clear_all();
for (uint i=0; i < table->s->fields; i++)
incr_table->field[i]->flags &= ~PART_KEY_FLAG;
if (create_table)
{
incr_table->file->extra(HA_EXTRA_WRITE_CACHE);
incr_table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
}
TABLE *rec_table= 0;
if (! (rec_table= create_tmp_table(thd_arg, &tmp_table_param, *column_types,
(ORDER*) 0, false, 1,
options, HA_POS_ERROR, alias,
true, keep_row_order)))
return true;
rec_table->keys_in_use_for_query.clear_all();
for (uint i=0; i < table->s->fields; i++)
rec_table->field[i]->flags &= ~PART_KEY_FLAG;
if (rec_tables.push_back(rec_table))
return true;
return false;
}
/**
Reset and empty the temporary table that stores the materialized query
result.
@note The cleanup performed here is exactly the same as for the two temp
tables of JOIN - exec_tmp_table_[1 | 2].
*/
void select_unit::cleanup()
{
table->file->extra(HA_EXTRA_RESET_STATE);
table->file->ha_delete_all_rows();
}
void select_union_recursive::cleanup()
{
if (table)
{
select_unit::cleanup();
free_tmp_table(thd, table);
}
if (incr_table)
{
incr_table->file->extra(HA_EXTRA_RESET_STATE);
incr_table->file->ha_delete_all_rows();
free_tmp_table(thd, incr_table);
}
List_iterator<TABLE> it(rec_tables);
TABLE *tab;
while ((tab= it++))
{
if (tab->is_created())
{
tab->file->extra(HA_EXTRA_RESET_STATE);
tab->file->ha_delete_all_rows();
}
/*
The table will be closed later in close_thread_tables(),
because it might be used in the statements like
ANALYZE WITH r AS (...) SELECT * from r
where r is defined through recursion.
*/
tab->next= thd->rec_tables;
thd->rec_tables= tab;
}
}
/**
Replace the current result with new_result and prepare it.
@param new_result New result pointer
@retval FALSE Success
@retval TRUE Error
*/
bool select_union_direct::change_result(select_result *new_result)
{
result= new_result;
return (result->prepare(unit->types, unit) || result->prepare2());
}
bool select_union_direct::postponed_prepare(List<Item> &types)
{
if (result != NULL)
return (result->prepare(types, unit) || result->prepare2());
else
return false;
}
bool select_union_direct::send_result_set_metadata(List<Item> &list, uint flags)
{
if (done_send_result_set_metadata)
return false;
done_send_result_set_metadata= true;
/*
Set global offset and limit to be used in send_data(). These can
be variables in prepared statements or stored programs, so they
must be reevaluated for each execution.
*/
offset= unit->global_parameters()->get_offset();
limit= unit->global_parameters()->get_limit();
if (limit + offset >= limit)
limit+= offset;
else
limit= HA_POS_ERROR; /* purecov: inspected */
return result->send_result_set_metadata(unit->types, flags);
}
int select_union_direct::send_data(List<Item> &items)
{
if (!limit)
return false;
limit--;
if (offset)
{
offset--;
return false;
}
send_records++;
fill_record(thd, table, table->field, items, true, false);
if (thd->is_error())
return true; /* purecov: inspected */
return result->send_data(unit->item_list);
}
bool select_union_direct::initialize_tables (JOIN *join)
{
if (done_initialize_tables)
return false;
done_initialize_tables= true;
return result->initialize_tables(join);
}
bool select_union_direct::send_eof()
{
// Reset for each SELECT_LEX, so accumulate here
limit_found_rows+= thd->limit_found_rows;
if (unit->thd->lex->current_select == last_select_lex)
{
thd->limit_found_rows= limit_found_rows;
// Reset and make ready for re-execution
done_send_result_set_metadata= false;
done_initialize_tables= false;
return result->send_eof();
}
else
return false;
}
/*
initialization procedures before fake_select_lex preparation()
SYNOPSIS
st_select_lex_unit::init_prepare_fake_select_lex()
thd - thread handler
first_execution - TRUE at the first execution of the union
RETURN
options of SELECT
*/
void
st_select_lex_unit::init_prepare_fake_select_lex(THD *thd_arg,
bool first_execution)
{
thd_arg->lex->current_select= fake_select_lex;
fake_select_lex->table_list.link_in_list(&result_table_list,
&result_table_list.next_local);
fake_select_lex->context.table_list=
fake_select_lex->context.first_name_resolution_table=
fake_select_lex->get_table_list();
/*
The flag fake_select_lex->first_execution indicates whether this is
called at the first execution of the statement, while first_execution
shows whether this is called at the first execution of the union that
may form just a subselect.
*/
if (!fake_select_lex->first_execution && first_execution)
{
for (ORDER *order= global_parameters()->order_list.first;
order;
order= order->next)
order->item= &order->item_ptr;
}
for (ORDER *order= global_parameters()->order_list.first;
order;
order=order->next)
{
(*order->item)->walk(&Item::change_context_processor, 0,
&fake_select_lex->context);
(*order->item)->walk(&Item::set_fake_select_as_master_processor, 0,
fake_select_lex);
}
}
bool st_select_lex_unit::prepare_join(THD *thd_arg, SELECT_LEX *sl,
select_result *tmp_result,
ulong additional_options,
bool is_union_select)
{
DBUG_ENTER("st_select_lex_unit::prepare_join");
bool can_skip_order_by;
sl->options|= SELECT_NO_UNLOCK;
JOIN *join= new JOIN(thd_arg, sl->item_list,
(sl->options | thd_arg->variables.option_bits |
additional_options),
tmp_result);
if (!join)
DBUG_RETURN(true);
thd_arg->lex->current_select= sl;
can_skip_order_by= is_union_select && !(sl->braces && sl->explicit_limit);
saved_error= join->prepare(sl->table_list.first,
sl->with_wild,
sl->where,
(can_skip_order_by ? 0 :
sl->order_list.elements) +
sl->group_list.elements,
can_skip_order_by ?
NULL : sl->order_list.first,
can_skip_order_by,
sl->group_list.first,
sl->having,
(is_union_select ? NULL :
thd_arg->lex->proc_list.first),
sl, this);
/* There are no * in the statement anymore (for PS) */
sl->with_wild= 0;
last_procedure= join->procedure;
if (saved_error || (saved_error= thd_arg->is_fatal_error))
DBUG_RETURN(true);
/*
Remove all references from the select_lex_units to the subqueries that
are inside the ORDER BY clause.
*/
if (can_skip_order_by)
{
for (ORDER *ord= (ORDER *)sl->order_list.first; ord; ord= ord->next)
{
(*ord->item)->walk(&Item::eliminate_subselect_processor, FALSE, NULL);
}
}
DBUG_RETURN(false);
}
class Type_holder: public Sql_alloc,
public Item_args,
public Type_handler_hybrid_field_type,
public Type_all_attributes,
public Type_geometry_attributes
{
TYPELIB *m_typelib;
bool m_maybe_null;
public:
Type_holder()
:m_typelib(NULL),
m_maybe_null(false)
{ }
void set_maybe_null(bool maybe_null_arg) { m_maybe_null= maybe_null_arg; }
bool get_maybe_null() const { return m_maybe_null; }
uint decimal_precision() const
{
/*
Type_holder is not used directly to create fields, so
its virtual decimal_precision() is never called.
We should eventually extend create_result_table() to accept
an array of Type_holders directly, without having to allocate
Item_type_holder's and put them into List<Item>.
*/
DBUG_ASSERT(0);
return 0;
}
void set_geometry_type(uint type)
{
Type_geometry_attributes::set_geometry_type(type);
}
uint uint_geometry_type() const
{
return Type_geometry_attributes::get_geometry_type();
}
void set_typelib(TYPELIB *typelib)
{
m_typelib= typelib;
}
TYPELIB *get_typelib() const
{
return m_typelib;
}
bool aggregate_attributes(THD *thd)
{
for (uint i= 0; i < arg_count; i++)
m_maybe_null|= args[i]->maybe_null;
return
type_handler()->Item_hybrid_func_fix_attributes(thd,
"UNION", this, this,
args, arg_count);
}
};
/**
Aggregate data type handlers for the "count" leftmost UNION parts.
*/
bool st_select_lex_unit::join_union_type_handlers(THD *thd_arg,
Type_holder *holders,
uint count)
{
DBUG_ENTER("st_select_lex_unit::join_union_type_handlers");
SELECT_LEX *first_sl= first_select(), *sl= first_sl;
for (uint i= 0; i < count ; sl= sl->next_select(), i++)
{
Item *item;
List_iterator_fast<Item> it(sl->item_list);
for (uint pos= 0; (item= it++); pos++)
{
const Type_handler *item_type_handler= item->real_type_handler();
if (sl == first_sl)
holders[pos].set_handler(item_type_handler);
else
{
if (first_sl->item_list.elements != sl->item_list.elements)
{
my_message(ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT,
ER_THD(thd_arg, ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT),
MYF(0));
DBUG_RETURN(true);
}
if (holders[pos].aggregate_for_result(item_type_handler))
{
my_error(ER_ILLEGAL_PARAMETER_DATA_TYPES2_FOR_OPERATION, MYF(0),
holders[pos].type_handler()->name().ptr(),
item_type_handler->name().ptr(),
"UNION");
DBUG_RETURN(true);
}
}
}
}
DBUG_RETURN(false);
}
/**
Aggregate data type attributes for the "count" leftmost UNION parts.
*/
bool st_select_lex_unit::join_union_type_attributes(THD *thd_arg,
Type_holder *holders,
uint count)
{
DBUG_ENTER("st_select_lex_unit::join_union_type_attributes");
SELECT_LEX *sl, *first_sl= first_select();
uint item_pos;
for (uint pos= 0; pos < first_sl->item_list.elements; pos++)
{
if (holders[pos].alloc_arguments(thd_arg, count))
DBUG_RETURN(true);
}
for (item_pos= 0, sl= first_sl ;
item_pos < count;
sl= sl->next_select(), item_pos++)
{
Item *item_tmp;
List_iterator_fast<Item> itx(sl->item_list);
for (uint holder_pos= 0 ; (item_tmp= itx++); holder_pos++)
{
DBUG_ASSERT(item_tmp->fixed);
holders[holder_pos].add_argument(item_tmp);
}
}
for (uint pos= 0; pos < first_sl->item_list.elements; pos++)
{
if (holders[pos].aggregate_attributes(thd_arg))
DBUG_RETURN(true);
}
DBUG_RETURN(false);
}
/**
Join data types for the leftmost "count" UNION parts
and store corresponding Item_type_holder's into "types".
*/
bool st_select_lex_unit::join_union_item_types(THD *thd_arg,
List<Item> &types,
uint count)
{
DBUG_ENTER("st_select_lex_unit::join_union_select_list_types");
SELECT_LEX *first_sl= first_select();
Type_holder *holders;
if (!(holders= new (thd_arg->mem_root)
Type_holder[first_sl->item_list.elements]) ||
join_union_type_handlers(thd_arg, holders, count) ||
join_union_type_attributes(thd_arg, holders, count))
DBUG_RETURN(true);
types.empty();
List_iterator_fast<Item> it(first_sl->item_list);
Item *item_tmp;
for (uint pos= 0; (item_tmp= it++); pos++)
{
/* Error's in 'new' will be detected after loop */
types.push_back(new (thd_arg->mem_root)
Item_type_holder(thd_arg,
&item_tmp->name,
holders[pos].type_handler(),
&holders[pos]/*Type_all_attributes*/,
holders[pos].get_maybe_null()));
}
if (thd_arg->is_fatal_error)
DBUG_RETURN(true); // out of memory
DBUG_RETURN(false);
}
bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
ulong additional_options)
{
SELECT_LEX *lex_select_save= thd_arg->lex->current_select;
SELECT_LEX *sl, *first_sl= first_select();
bool is_recursive= with_element && with_element->is_recursive;
bool is_rec_result_table_created= false;
uint union_part_count= 0;
select_result *tmp_result;
bool is_union_select;
bool have_except= FALSE, have_intersect= FALSE;
bool instantiate_tmp_table= false;
DBUG_ENTER("st_select_lex_unit::prepare");
DBUG_ASSERT(thd == thd_arg);
DBUG_ASSERT(thd == current_thd);
describe= additional_options & SELECT_DESCRIBE;
/*
Save fake_select_lex in case we don't need it for anything but
global parameters.
*/
if (saved_fake_select_lex == NULL) // Don't overwrite on PS second prepare
saved_fake_select_lex= fake_select_lex;
/*
result object should be reassigned even if preparing already done for
max/min subquery (ALL/ANY optimization)
*/
result= sel_result;
if (prepared)
{
if (describe)
{
/* fast reinit for EXPLAIN */
for (sl= first_sl; sl; sl= sl->next_select())
{
sl->join->result= result;
select_limit_cnt= HA_POS_ERROR;
offset_limit_cnt= 0;
if (!sl->join->procedure &&
result->prepare(sl->join->fields_list, this))
{
DBUG_RETURN(TRUE);
}
sl->join->select_options|= SELECT_DESCRIBE;
sl->join->reinit();
}
}
DBUG_RETURN(FALSE);
}
prepared= 1;
saved_error= FALSE;
thd_arg->lex->current_select= sl= first_sl;
found_rows_for_union= first_sl->options & OPTION_FOUND_ROWS;
is_union_select= is_unit_op() || fake_select_lex;
for (SELECT_LEX *s= first_sl; s; s= s->next_select())
{
switch (s->linkage)
{
case INTERSECT_TYPE:
have_intersect= TRUE;
break;
case EXCEPT_TYPE:
have_except= TRUE;
break;
default:
break;
}
}
/* Global option */
if (is_union_select || is_recursive)
{
if (is_unit_op() && !union_needs_tmp_table() &&
!have_except && !have_intersect)
{
SELECT_LEX *last= first_select();
while (last->next_select())
last= last->next_select();
if (!(tmp_result= union_result=
new (thd_arg->mem_root) select_union_direct(thd_arg, sel_result,
last)))
goto err; /* purecov: inspected */
fake_select_lex= NULL;
instantiate_tmp_table= false;
}
else
{
if (!is_recursive)
union_result= new (thd_arg->mem_root) select_unit(thd_arg);
else
{
with_element->rec_result=
new (thd_arg->mem_root) select_union_recursive(thd_arg);
union_result= with_element->rec_result;
fake_select_lex= NULL;
}
if (!(tmp_result= union_result))
goto err; /* purecov: inspected */
instantiate_tmp_table= true;
}
}
else
tmp_result= sel_result;
sl->context.resolve_in_select_list= TRUE;
if (!is_union_select && !is_recursive)
{
if (prepare_join(thd_arg, first_sl, tmp_result, additional_options,
is_union_select))
goto err;
types= first_sl->item_list;
goto cont;
}
for (;sl; sl= sl->next_select(), union_part_count++)
{
if (prepare_join(thd_arg, sl, tmp_result, additional_options,
is_union_select))
goto err;
/*
setup_tables_done_option should be set only for very first SELECT,
because it protect from secont setup_tables call for select-like non
select commands (DELETE/INSERT/...) and they use only very first
SELECT (for union it can be only INSERT ... SELECT).
*/
additional_options&= ~OPTION_SETUP_TABLES_DONE;
/*
Use items list of underlaid select for derived tables to preserve
information about fields lengths and exact types
*/
if (sl == first_sl)
{
if (is_recursive)
{
if (derived->with->rename_columns_of_derived_unit(thd, this))
goto err;
if (check_duplicate_names(thd, sl->item_list, 0))
goto err;
}
}
if (is_recursive)
{
if (!with_element->is_anchor(sl))
sl->uncacheable|= UNCACHEABLE_UNITED;
if(!is_rec_result_table_created &&
(!sl->next_select() ||
sl->next_select() == with_element->first_recursive))
{
ulonglong create_options;
create_options= (first_sl->options | thd_arg->variables.option_bits |
TMP_TABLE_ALL_COLUMNS);
// Join data types for all non-recursive parts of a recursive UNION
if (join_union_item_types(thd, types, union_part_count + 1))
goto err;
if (union_result->create_result_table(thd, &types,
MY_TEST(union_distinct),
create_options, derived->alias,
false,
instantiate_tmp_table, false,
0))
goto err;
if (!derived->table)
derived->table= derived->derived_result->table=
with_element->rec_result->rec_tables.head();
with_element->mark_as_with_prepared_anchor();
is_rec_result_table_created= true;
}
}
}
// In case of a non-recursive UNION, join data types for all UNION parts.
if (!is_recursive && join_union_item_types(thd, types, union_part_count))
goto err;
cont:
/*
If the query is using select_union_direct, we have postponed
preparation of the underlying select_result until column types
are known.
*/
if (union_result != NULL && union_result->postponed_prepare(types))
DBUG_RETURN(true);
if (is_union_select)
{
/*
Check that it was possible to aggregate
all collations together for UNION.
*/
List_iterator_fast<Item> tp(types);
Item *type;
ulonglong create_options;
uint save_tablenr= 0;
table_map save_map= 0;
uint save_maybe_null= 0;
while ((type= tp++))
{
if (type->cmp_type() == STRING_RESULT &&
type->collation.derivation == DERIVATION_NONE)
{
my_error(ER_CANT_AGGREGATE_NCOLLATIONS, MYF(0), "UNION");
goto err;
}
}
/*
Disable the usage of fulltext searches in the last union branch.
This is a temporary 5.x limitation because of the way the fulltext
search functions are handled by the optimizer.
This is manifestation of the more general problems of "taking away"
parts of a SELECT statement post-fix_fields(). This is generally not
doable since various flags are collected in various places (e.g.
SELECT_LEX) that carry information about the presence of certain
expressions or constructs in the parts of the query.
When part of the query is taken away it's not clear how to "divide"
the meaning of these accumulated flags and what to carry over to the
recipient query (SELECT_LEX).
*/
if (global_parameters()->ftfunc_list->elements &&
global_parameters()->order_list.elements &&
global_parameters() != fake_select_lex)
{
ORDER *ord;
Item_func::Functype ft= Item_func::FT_FUNC;
for (ord= global_parameters()->order_list.first; ord; ord= ord->next)
if ((*ord->item)->walk (&Item::find_function_processor, FALSE, &ft))
{
my_error (ER_CANT_USE_OPTION_HERE, MYF(0), "MATCH()");
goto err;
}
}
create_options= (first_sl->options | thd_arg->variables.option_bits |
TMP_TABLE_ALL_COLUMNS);
/*
Force the temporary table to be a MyISAM table if we're going to use
fullext functions (MATCH ... AGAINST .. IN BOOLEAN MODE) when reading
from it (this should be removed in 5.2 when fulltext search is moved
out of MyISAM).
*/
if (global_parameters()->ftfunc_list->elements)
create_options= create_options | TMP_TABLE_FORCE_MYISAM;
if (!is_recursive)
{
uint hidden= 0;
if (have_intersect)
{
hidden= 1;
if (!intersect_mark)
{
/*
For intersect we add a hidden column first that contains
the current select number of the time when the row was
added to the temporary table
*/
Query_arena *arena, backup_arena;
arena= thd->activate_stmt_arena_if_needed(&backup_arena);
intersect_mark= new (thd_arg->mem_root) Item_int(thd, 0);
if (arena)
thd->restore_active_arena(arena, &backup_arena);
if (!intersect_mark)
goto err;
}
else
intersect_mark->value= 0; //reset
types.push_front(union_result->intersect_mark= intersect_mark);
union_result->intersect_mark->name.str= "___";
union_result->intersect_mark->name.length= 3;
}
bool error=
union_result->create_result_table(thd, &types,
MY_TEST(union_distinct),
create_options, "", false,
instantiate_tmp_table, false,
hidden);
if (intersect_mark)
types.pop();
if (error)
goto err;
}
if (fake_select_lex && !fake_select_lex->first_cond_optimization)
{
save_tablenr= result_table_list.tablenr_exec;
save_map= result_table_list.map_exec;
save_maybe_null= result_table_list.maybe_null_exec;
}
bzero((char*) &result_table_list, sizeof(result_table_list));
result_table_list.db= (char*) "";
result_table_list.table_name= result_table_list.alias= (char*) "union";
result_table_list.table= table= union_result->table;
if (fake_select_lex && !fake_select_lex->first_cond_optimization)
{
result_table_list.tablenr_exec= save_tablenr;
result_table_list.map_exec= save_map;
result_table_list.maybe_null_exec= save_maybe_null;
}
thd_arg->lex->current_select= lex_select_save;
if (!item_list.elements)
{
Query_arena *arena, backup_arena;
arena= thd->activate_stmt_arena_if_needed(&backup_arena);
saved_error= table->fill_item_list(&item_list);
// Item_list is inherited from 'types', so there could be the counter
if (intersect_mark)
item_list.pop(); // remove intersect counter
if (arena)
thd->restore_active_arena(arena, &backup_arena);
if (saved_error)
goto err;
if (fake_select_lex != NULL &&
(thd->stmt_arena->is_stmt_prepare() ||
(thd->lex->context_analysis_only & CONTEXT_ANALYSIS_ONLY_VIEW)))
{
/* Validate the global parameters of this union */
init_prepare_fake_select_lex(thd, TRUE);
/* Should be done only once (the only item_list per statement) */
DBUG_ASSERT(fake_select_lex->join == 0);
if (!(fake_select_lex->join= new JOIN(thd, item_list, thd->variables.option_bits,
result)))
{
fake_select_lex->table_list.empty();
DBUG_RETURN(TRUE);
}
/*
Fake st_select_lex should have item list for correct ref_array
allocation.
*/
fake_select_lex->item_list= item_list;
thd_arg->lex->current_select= fake_select_lex;
/*
We need to add up n_sum_items in order to make the correct
allocation in setup_ref_array().
*/
fake_select_lex->n_child_sum_items+= global_parameters()->n_sum_items;
saved_error= fake_select_lex->join->
prepare(fake_select_lex->table_list.first,
0, 0,
global_parameters()->order_list.elements, // og_num
global_parameters()->order_list.first, // order
false, NULL, NULL, NULL,
fake_select_lex, this);
fake_select_lex->table_list.empty();
}
}
else
{
/*
We're in execution of a prepared statement or stored procedure:
reset field items to point at fields from the created temporary table.
*/
table->reset_item_list(&item_list, intersect_mark ? 1 : 0);
}
}
thd_arg->lex->current_select= lex_select_save;
DBUG_RETURN(saved_error || thd_arg->is_fatal_error);
err:
thd_arg->lex->current_select= lex_select_save;
(void) cleanup();
DBUG_RETURN(TRUE);
}
/**
Run optimization phase.
@return FALSE unit successfully passed optimization phase.
@return TRUE an error occur.
*/
bool st_select_lex_unit::optimize()
{
SELECT_LEX *lex_select_save= thd->lex->current_select;
SELECT_LEX *select_cursor=first_select();
DBUG_ENTER("st_select_lex_unit::optimize");
if (optimized && !uncacheable && !describe)
DBUG_RETURN(FALSE);
if (with_element && with_element->is_recursive && optimize_started)
DBUG_RETURN(FALSE);
optimize_started= true;
if (uncacheable || !item || !item->assigned() || describe)
{
if (item)
item->reset_value_registration();
if (optimized && item)
{
if (item->assigned())
{
item->assigned(0); // We will reinit & rexecute unit
item->reset();
if (table->is_created())
{
table->file->ha_delete_all_rows();
table->file->info(HA_STATUS_VARIABLE);
}
}
/* re-enabling indexes for next subselect iteration */
if (union_distinct && table->file->ha_enable_indexes(HA_KEY_SWITCH_ALL))
{
DBUG_ASSERT(0);
}
}
for (SELECT_LEX *sl= select_cursor; sl; sl= sl->next_select())
{
thd->lex->current_select= sl;
if (optimized)
saved_error= sl->join->reinit();
else
{
set_limit(sl);
if (sl == global_parameters() || describe)
{
offset_limit_cnt= 0;
/*
We can't use LIMIT at this stage if we are using ORDER BY for the
whole query
*/
if (sl->order_list.first || describe)
select_limit_cnt= HA_POS_ERROR;
}
/*
When using braces, SQL_CALC_FOUND_ROWS affects the whole query:
we don't calculate found_rows() per union part.
Otherwise, SQL_CALC_FOUND_ROWS should be done on all sub parts.
*/
sl->join->select_options=
(select_limit_cnt == HA_POS_ERROR || sl->braces) ?
sl->options & ~OPTION_FOUND_ROWS : sl->options | found_rows_for_union;
saved_error= sl->join->optimize();
}
if (saved_error)
{
thd->lex->current_select= lex_select_save;
DBUG_RETURN(saved_error);
}
}
}
optimized= 1;
thd->lex->current_select= lex_select_save;
DBUG_RETURN(saved_error);
}
bool st_select_lex_unit::exec()
{
SELECT_LEX *lex_select_save= thd->lex->current_select;
SELECT_LEX *select_cursor=first_select();
ulonglong add_rows=0;
ha_rows examined_rows= 0;
bool first_execution= !executed;
DBUG_ENTER("st_select_lex_unit::exec");
bool was_executed= executed;
if (executed && !uncacheable && !describe)
DBUG_RETURN(FALSE);
executed= 1;
if (!(uncacheable & ~UNCACHEABLE_EXPLAIN) && item &&
!item->with_recursive_reference)
item->make_const();
saved_error= optimize();
create_explain_query_if_not_exists(thd->lex, thd->mem_root);
if (!saved_error && !was_executed)
save_union_explain(thd->lex->explain);
if (saved_error)
DBUG_RETURN(saved_error);
if (uncacheable || !item || !item->assigned() || describe)
{
if (!fake_select_lex && !(with_element && with_element->is_recursive))
union_result->cleanup();
for (SELECT_LEX *sl= select_cursor; sl; sl= sl->next_select())
{
ha_rows records_at_start= 0;
thd->lex->current_select= sl;
if (union_result)
union_result->change_select();
if (fake_select_lex)
{
if (sl != &thd->lex->select_lex)
fake_select_lex->uncacheable|= sl->uncacheable;
else
fake_select_lex->uncacheable= 0;
}
{
set_limit(sl);
if (sl == global_parameters() || describe)
{
offset_limit_cnt= 0;
/*
We can't use LIMIT at this stage if we are using ORDER BY for the
whole query
*/
if (sl->order_list.first || describe)
select_limit_cnt= HA_POS_ERROR;
}
/*
When using braces, SQL_CALC_FOUND_ROWS affects the whole query:
we don't calculate found_rows() per union part.
Otherwise, SQL_CALC_FOUND_ROWS should be done on all sub parts.
*/
sl->join->select_options=
(select_limit_cnt == HA_POS_ERROR || sl->braces) ?
sl->options & ~OPTION_FOUND_ROWS : sl->options | found_rows_for_union;
saved_error= sl->join->optimize();
}
if (!saved_error)
{
records_at_start= table->file->stats.records;
sl->join->exec();
if (sl == union_distinct && !(with_element && with_element->is_recursive))
{
// This is UNION DISTINCT, so there should be a fake_select_lex
DBUG_ASSERT(fake_select_lex != NULL);
if (table->file->ha_disable_indexes(HA_KEY_SWITCH_ALL))
DBUG_RETURN(TRUE);
table->no_keyread=1;
}
saved_error= sl->join->error;
offset_limit_cnt= (ha_rows)(sl->offset_limit ?
sl->offset_limit->val_uint() :
0);
if (!saved_error)
{
examined_rows+= thd->get_examined_row_count();
thd->set_examined_row_count(0);
if (union_result->flush())
{
thd->lex->current_select= lex_select_save;
DBUG_RETURN(1);
}
}
}
if (saved_error)
{
thd->lex->current_select= lex_select_save;
DBUG_RETURN(saved_error);
}
if (fake_select_lex != NULL)
{
/* Needed for the following test and for records_at_start in next loop */
int error= table->file->info(HA_STATUS_VARIABLE);
if(error)
{
table->file->print_error(error, MYF(0));
DBUG_RETURN(1);
}
}
if (found_rows_for_union && !sl->braces &&
select_limit_cnt != HA_POS_ERROR)
{
/*
This is a union without braces. Remember the number of rows that
could also have been part of the result set.
We get this from the difference of between total number of possible
rows and actual rows added to the temporary table.
*/
add_rows+= (ulonglong) (thd->limit_found_rows - (ulonglong)
((table->file->stats.records - records_at_start)));
}
if (thd->killed == ABORT_QUERY)
{
/*
Stop execution of the remaining queries in the UNIONS, and produce
the current result.
*/
push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
ER_QUERY_EXCEEDED_ROWS_EXAMINED_LIMIT,
ER_THD(thd, ER_QUERY_EXCEEDED_ROWS_EXAMINED_LIMIT),
thd->accessed_rows_and_keys,
thd->lex->limit_rows_examined->val_uint());
thd->reset_killed();
break;
}
}
}
DBUG_EXECUTE_IF("show_explain_probe_union_read",
dbug_serve_apcs(thd, 1););
{
List<Item_func_match> empty_list;
empty_list.empty();
/*
Disable LIMIT ROWS EXAMINED in order to produce the possibly incomplete
result of the UNION without interruption due to exceeding the limit.
*/
thd->lex->limit_rows_examined_cnt= ULONGLONG_MAX;
if (fake_select_lex != NULL && !thd->is_fatal_error) // Check if EOM
{
/* Send result to 'result' */
saved_error= true;
set_limit(global_parameters());
init_prepare_fake_select_lex(thd, first_execution);
JOIN *join= fake_select_lex->join;
saved_error= false;
if (!join)
{
/*
allocate JOIN for fake select only once (prevent
mysql_select automatic allocation)
TODO: The above is nonsense. mysql_select() will not allocate the
join if one already exists. There must be some other reason why we
don't let it allocate the join. Perhaps this is because we need
some special parameter values passed to join constructor?
*/
if (!(fake_select_lex->join= new JOIN(thd, item_list,
fake_select_lex->options, result)))
{
fake_select_lex->table_list.empty();
goto err;
}
fake_select_lex->join->no_const_tables= TRUE;
/*
Fake st_select_lex should have item list for correct ref_array
allocation.
*/
fake_select_lex->item_list= item_list;
/*
We need to add up n_sum_items in order to make the correct
allocation in setup_ref_array().
Don't add more sum_items if we have already done JOIN::prepare
for this (with a different join object)
*/
if (fake_select_lex->ref_pointer_array.is_null())
fake_select_lex->n_child_sum_items+= global_parameters()->n_sum_items;
if (!was_executed)
save_union_explain_part2(thd->lex->explain);
saved_error= mysql_select(thd,
&result_table_list,
0, item_list, NULL,
global_parameters()->order_list.elements,
global_parameters()->order_list.first,
NULL, NULL, NULL,
fake_select_lex->options | SELECT_NO_UNLOCK,
result, this, fake_select_lex);
}
else
{
if (describe)
{
/*
In EXPLAIN command, constant subqueries that do not use any
tables are executed two times:
- 1st time is a real evaluation to get the subquery value
- 2nd time is to produce EXPLAIN output rows.
1st execution sets certain members (e.g. select_result) to perform
subquery execution rather than EXPLAIN line production. In order
to reset them back, we re-do all of the actions (yes it is ugly):
*/ // psergey-todo: is the above really necessary anymore??
join->init(thd, item_list, fake_select_lex->options, result);
saved_error= mysql_select(thd,
&result_table_list,
0, item_list, NULL,
global_parameters()->order_list.elements,
global_parameters()->order_list.first,
NULL, NULL, NULL,
fake_select_lex->options | SELECT_NO_UNLOCK,
result, this, fake_select_lex);
}
else
{
join->join_examined_rows= 0;
saved_error= join->reinit();
join->exec();
}
}
fake_select_lex->table_list.empty();
if (!saved_error)
{
thd->limit_found_rows = (ulonglong)table->file->stats.records + add_rows;
thd->inc_examined_row_count(examined_rows);
}
/*
Mark for slow query log if any of the union parts didn't use
indexes efficiently
*/
}
}
thd->lex->current_select= lex_select_save;
err:
thd->lex->set_limit_rows_examined();
DBUG_RETURN(saved_error);
}
/**
@brief
Execute the union of the specification of a recursive with table
@details
The method is performed only for the units that are specifications
if recursive with table T. If the specification contains an anchor
part then the first call of this method executes only this part
while the following calls execute the recursive part. If there are
no anchors each call executes the whole unit.
Before the excution the method cleans up the temporary table
to where the new rows of the recursive table are sent.
After the execution the unit these rows are copied to the
temporary tables created for recursive references of T.
If the specification if T is restricted (standards compliant)
then these temporary tables are cleaned up before new rows
are copied into them.
@retval
false on success
true on failure
*/
bool st_select_lex_unit::exec_recursive()
{
st_select_lex *lex_select_save= thd->lex->current_select;
st_select_lex *start= with_element->first_recursive;
TABLE *incr_table= with_element->rec_result->incr_table;
st_select_lex *end= NULL;
bool is_unrestricted= with_element->is_unrestricted();
List_iterator_fast<TABLE> li(with_element->rec_result->rec_tables);
TMP_TABLE_PARAM *tmp_table_param= &with_element->rec_result->tmp_table_param;
ha_rows examined_rows= 0;
bool was_executed= executed;
TABLE *rec_table;
DBUG_ENTER("st_select_lex_unit::exec_recursive");
executed= 1;
create_explain_query_if_not_exists(thd->lex, thd->mem_root);
if (!was_executed)
save_union_explain(thd->lex->explain);
if ((saved_error= incr_table->file->ha_delete_all_rows()))
goto err;
if (with_element->level == 0)
{
start= first_select();
if (with_element->with_anchor)
end= with_element->first_recursive;
}
for (st_select_lex *sl= start ; sl != end; sl= sl->next_select())
{
thd->lex->current_select= sl;
sl->join->exec();
saved_error= sl->join->error;
if (!saved_error)
{
examined_rows+= thd->get_examined_row_count();
thd->set_examined_row_count(0);
if (union_result->flush())
{
thd->lex->current_select= lex_select_save;
DBUG_RETURN(1);
}
}
if (saved_error)
{
thd->lex->current_select= lex_select_save;
goto err;
}
}
thd->inc_examined_row_count(examined_rows);
incr_table->file->info(HA_STATUS_VARIABLE);
if (with_element->level && incr_table->file->stats.records == 0)
with_element->set_as_stabilized();
else
with_element->level++;
while ((rec_table= li++))
{
saved_error=
incr_table->insert_all_rows_into_tmp_table(thd, rec_table,
tmp_table_param,
!is_unrestricted);
if (!with_element->rec_result->first_rec_table_to_update)
with_element->rec_result->first_rec_table_to_update= rec_table;
if (with_element->level == 1 && rec_table->reginfo.join_tab)
rec_table->reginfo.join_tab->preread_init_done= true;
}
for (Item_subselect *sq= with_element->sq_with_rec_ref.first;
sq;
sq= sq->next_with_rec_ref)
{
sq->engine->force_reexecution();
}
thd->lex->current_select= lex_select_save;
err:
thd->lex->set_limit_rows_examined();
DBUG_RETURN(saved_error);
}
bool st_select_lex_unit::cleanup()
{
int error= 0;
DBUG_ENTER("st_select_lex_unit::cleanup");
if (cleaned)
{
DBUG_RETURN(FALSE);
}
cleaned= 1;
for (SELECT_LEX *sl= first_select(); sl; sl= sl->next_select())
error|= sl->cleanup();
if (fake_select_lex)
{
error|= fake_select_lex->cleanup();
/*
There are two cases when we should clean order items:
1. UNION with SELECTs which all enclosed into braces
in this case global_parameters == fake_select_lex
2. UNION where last SELECT is not enclosed into braces
in this case global_parameters == 'last select'
So we should use global_parameters->order_list for
proper order list clean up.
Note: global_parameters and fake_select_lex are always
initialized for UNION
*/
DBUG_ASSERT(global_parameters());
if (global_parameters()->order_list.elements)
{
ORDER *ord;
for (ord= global_parameters()->order_list.first; ord; ord= ord->next)
(*ord->item)->walk (&Item::cleanup_processor, 0, 0);
}
}
if (with_element && with_element->is_recursive)
{
if (union_result )
{
((select_union_recursive *) union_result)->cleanup();
delete union_result;
union_result= 0;
}
with_element->mark_as_cleaned();
}
else
{
if (union_result)
{
delete union_result;
union_result=0; // Safety
if (table)
free_tmp_table(thd, table);
table= 0; // Safety
}
}
DBUG_RETURN(error);
}
void st_select_lex_unit::reinit_exec_mechanism()
{
prepared= optimized= optimized_2= executed= 0;
optimize_started= 0;
#ifndef DBUG_OFF
if (is_unit_op())
{
List_iterator_fast<Item> it(item_list);
Item *field;
while ((field= it++))
{
/*
we can't cleanup here, because it broke link to temporary table field,
but have to drop fixed flag to allow next fix_field of this field
during re-executing
*/
field->fixed= 0;
}
}
#endif
if (with_element && with_element->is_recursive)
with_element->reset_recursive_for_exec();
}
/**
Change the select_result object used to return the final result of
the unit, replacing occurences of old_result with new_result.
@param new_result New select_result object
@param old_result Old select_result object
@retval false Success
@retval true Error
*/
bool st_select_lex_unit::change_result(select_result_interceptor *new_result,
select_result_interceptor *old_result)
{
for (SELECT_LEX *sl= first_select(); sl; sl= sl->next_select())
{
if (sl->join)
if (sl->join->change_result(new_result, old_result))
return true; /* purecov: inspected */
}
/*
If there were a fake_select_lex->join, we would have to change the
result of that also, but change_result() is called before such an
object is created.
*/
DBUG_ASSERT(fake_select_lex == NULL || fake_select_lex->join == NULL);
return false;
}
/*
Get column type information for this unit.
SYNOPSIS
st_select_lex_unit::get_column_types()
@param for_cursor if true return the list the fields
retrieved by the cursor
DESCRIPTION
For a single-select the column types are taken
from the list of selected items. For a union this function
assumes that st_select_lex_unit::prepare has been called
and returns the type holders that were created for unioned
column types of all selects.
NOTES
The implementation of this function should be in sync with
st_select_lex_unit::prepare()
*/
List<Item> *st_select_lex_unit::get_column_types(bool for_cursor)
{
SELECT_LEX *sl= first_select();
bool is_procedure= MY_TEST(sl->join->procedure);
if (is_procedure)
{
/* Types for "SELECT * FROM t1 procedure analyse()"
are generated during execute */
return &sl->join->procedure_fields_list;
}
if (is_unit_op())
{
DBUG_ASSERT(prepared);
/* Types are generated during prepare */
return &types;
}
return for_cursor ? sl->join->fields : &sl->item_list;
}
static void cleanup_order(ORDER *order)
{
for (; order; order= order->next)
order->counter_used= 0;
}
bool st_select_lex::cleanup()
{
bool error= FALSE;
DBUG_ENTER("st_select_lex::cleanup()");
cleanup_order(order_list.first);
cleanup_order(group_list.first);
if (join)
{
DBUG_ASSERT((st_select_lex*)join->select_lex == this);
error= join->destroy();
delete join;
join= 0;
}
for (SELECT_LEX_UNIT *lex_unit= first_inner_unit(); lex_unit ;
lex_unit= lex_unit->next_unit())
{
error= (bool) ((uint) error | (uint) lex_unit->cleanup());
}
inner_refs_list.empty();
exclude_from_table_unique_test= FALSE;
DBUG_RETURN(error);
}
void st_select_lex::cleanup_all_joins(bool full)
{
SELECT_LEX_UNIT *unit;
SELECT_LEX *sl;
DBUG_ENTER("st_select_lex::cleanup_all_joins");
if (join)
join->cleanup(full);
for (unit= first_inner_unit(); unit; unit= unit->next_unit())
for (sl= unit->first_select(); sl; sl= sl->next_select())
sl->cleanup_all_joins(full);
DBUG_VOID_RETURN;
}
/**
Set exclude_from_table_unique_test for selects of this unit and all
underlying selects.
@note used to exclude materialized derived tables (views) from unique
table check.
*/
void st_select_lex_unit::set_unique_exclude()
{
for (SELECT_LEX *sl= first_select(); sl; sl= sl->next_select())
{
sl->exclude_from_table_unique_test= TRUE;
for (SELECT_LEX_UNIT *unit= sl->first_inner_unit();
unit;
unit= unit->next_unit())
{
unit->set_unique_exclude();
}
}
}
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