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mariadb/sql/sql_window.cc
Galina Shalygina be1d06c8a5 Merge branch '10.2' into 10.2-mdev9864
2016-05-08 23:04:41 +03:00

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#include "sql_select.h"
#include "sql_list.h"
#include "item_windowfunc.h"
#include "filesort.h"
#include "sql_base.h"
#include "sql_window.h"
bool
Window_spec::check_window_names(List_iterator_fast<Window_spec> &it)
{
if (window_names_are_checked)
return false;
char *name= this->name();
char *ref_name= window_reference();
it.rewind();
Window_spec *win_spec;
while((win_spec= it++) && win_spec != this)
{
char *win_spec_name= win_spec->name();
if (!win_spec_name)
break;
if (name && my_strcasecmp(system_charset_info, name, win_spec_name) == 0)
{
my_error(ER_DUP_WINDOW_NAME, MYF(0), name);
return true;
}
if (ref_name &&
my_strcasecmp(system_charset_info, ref_name, win_spec_name) == 0)
{
if (partition_list->elements)
{
my_error(ER_PARTITION_LIST_IN_REFERENCING_WINDOW_SPEC, MYF(0),
ref_name);
return true;
}
if (win_spec->order_list->elements && order_list->elements)
{
my_error(ER_ORDER_LIST_IN_REFERENCING_WINDOW_SPEC, MYF(0), ref_name);
return true;
}
if (win_spec->window_frame)
{
my_error(ER_WINDOW_FRAME_IN_REFERENCED_WINDOW_SPEC, MYF(0), ref_name);
return true;
}
referenced_win_spec= win_spec;
if (partition_list->elements == 0)
partition_list= win_spec->partition_list;
if (order_list->elements == 0)
order_list= win_spec->order_list;
}
}
if (ref_name && !referenced_win_spec)
{
my_error(ER_WRONG_WINDOW_SPEC_NAME, MYF(0), ref_name);
return true;
}
window_names_are_checked= true;
return false;
}
bool
Window_frame::check_frame_bounds()
{
if ((top_bound->is_unbounded() &&
top_bound->precedence_type == Window_frame_bound::FOLLOWING) ||
(bottom_bound->is_unbounded() &&
bottom_bound->precedence_type == Window_frame_bound::PRECEDING) ||
(top_bound->precedence_type == Window_frame_bound::CURRENT &&
bottom_bound->precedence_type == Window_frame_bound::PRECEDING) ||
(bottom_bound->precedence_type == Window_frame_bound::CURRENT &&
top_bound->precedence_type == Window_frame_bound::FOLLOWING))
{
my_error(ER_BAD_COMBINATION_OF_WINDOW_FRAME_BOUND_SPECS, MYF(0));
return true;
}
return false;
}
/*
Setup window functions in a select
*/
int
setup_windows(THD *thd, Ref_ptr_array ref_pointer_array, TABLE_LIST *tables,
List<Item> &fields, List<Item> &all_fields,
List<Window_spec> &win_specs, List<Item_window_func> &win_funcs)
{
Window_spec *win_spec;
DBUG_ENTER("setup_windows");
List_iterator<Window_spec> it(win_specs);
/*
Move all unnamed specifications after the named ones.
We could have avoided it if we had built two separate lists for
named and unnamed specifications.
*/
Query_arena *arena, backup;
arena= thd->activate_stmt_arena_if_needed(&backup);
uint i = 0;
uint elems= win_specs.elements;
while ((win_spec= it++) && i++ < elems)
{
if (win_spec->name() == NULL)
{
it.remove();
win_specs.push_back(win_spec);
}
}
if (arena)
thd->restore_active_arena(arena, &backup);
it.rewind();
List_iterator_fast<Window_spec> itp(win_specs);
while ((win_spec= it++))
{
bool hidden_group_fields;
if (win_spec->check_window_names(itp) ||
setup_group(thd, ref_pointer_array, tables, fields, all_fields,
win_spec->partition_list->first, &hidden_group_fields,
true) ||
setup_order(thd, ref_pointer_array, tables, fields, all_fields,
win_spec->order_list->first, true) ||
(win_spec->window_frame &&
win_spec->window_frame->check_frame_bounds()))
{
DBUG_RETURN(1);
}
if (win_spec->window_frame &&
win_spec->window_frame->exclusion != Window_frame::EXCL_NONE)
{
my_error(ER_FRAME_EXCLUSION_NOT_SUPPORTED, MYF(0));
DBUG_RETURN(1);
}
/*
For "win_func() OVER (ORDER BY order_list RANGE BETWEEN ...)",
- ORDER BY order_list must not be ommitted
- the list must have a single element.
*/
if (win_spec->window_frame &&
win_spec->window_frame->units == Window_frame::UNITS_RANGE)
{
if (win_spec->order_list->elements != 1)
{
my_error(ER_RANGE_FRAME_NEEDS_SIMPLE_ORDERBY, MYF(0));
DBUG_RETURN(1);
}
/*
"The declared type of SK shall be numeric, datetime, or interval"
we don't support datetime or interval, yet.
*/
Item_result rtype= win_spec->order_list->first->item[0]->result_type();
if (rtype != REAL_RESULT && rtype != INT_RESULT &&
rtype != DECIMAL_RESULT)
{
my_error(ER_WRONG_TYPE_FOR_RANGE_FRAME, MYF(0));
DBUG_RETURN(1);
}
/*
"The declared type of UVS shall be numeric if the declared type of SK
is numeric; otherwise, it shall be an interval type that may be added
to or subtracted from the declared type of SK"
*/
Window_frame_bound *bounds[]= {win_spec->window_frame->top_bound,
win_spec->window_frame->bottom_bound,
NULL};
for (Window_frame_bound **pbound= &bounds[0]; *pbound; pbound++)
{
if (!(*pbound)->is_unbounded() &&
((*pbound)->precedence_type == Window_frame_bound::FOLLOWING ||
(*pbound)->precedence_type == Window_frame_bound::PRECEDING))
{
Item_result rtype= (*pbound)->offset->result_type();
if (rtype != REAL_RESULT && rtype != INT_RESULT &&
rtype != DECIMAL_RESULT)
{
my_error(ER_WRONG_TYPE_FOR_RANGE_FRAME, MYF(0));
DBUG_RETURN(1);
}
}
}
}
/* "ROWS PRECEDING|FOLLOWING $n" must have a numeric $n */
if (win_spec->window_frame &&
win_spec->window_frame->units == Window_frame::UNITS_ROWS)
{
Window_frame_bound *bounds[]= {win_spec->window_frame->top_bound,
win_spec->window_frame->bottom_bound,
NULL};
for (Window_frame_bound **pbound= &bounds[0]; *pbound; pbound++)
{
if (!(*pbound)->is_unbounded() &&
((*pbound)->precedence_type == Window_frame_bound::FOLLOWING ||
(*pbound)->precedence_type == Window_frame_bound::PRECEDING))
{
Item *offset= (*pbound)->offset;
if (offset->result_type() != INT_RESULT)
{
my_error(ER_WRONG_TYPE_FOR_ROWS_FRAME, MYF(0));
DBUG_RETURN(1);
}
}
}
}
}
List_iterator_fast<Item_window_func> li(win_funcs);
Item_window_func *win_func_item;
while ((win_func_item= li++))
{
win_func_item->update_used_tables();
}
DBUG_RETURN(0);
}
/////////////////////////////////////////////////////////////////////////////
// Sorting window functions to minimize the number of table scans
// performed during the computation of these functions
/////////////////////////////////////////////////////////////////////////////
#define CMP_LT -2 // Less than
#define CMP_LT_C -1 // Less than and compatible
#define CMP_EQ 0 // Equal to
#define CMP_GT_C 1 // Greater than and compatible
#define CMP_GT 2 // Greater then
static
int compare_order_elements(ORDER *ord1, ORDER *ord2)
{
if (*ord1->item == *ord2->item)
return CMP_EQ;
Item *item1= (*ord1->item)->real_item();
Item *item2= (*ord2->item)->real_item();
DBUG_ASSERT(item1->type() == Item::FIELD_ITEM &&
item2->type() == Item::FIELD_ITEM);
int cmp= ((Item_field *) item1)->field - ((Item_field *) item2)->field;
if (cmp == 0)
{
if (ord1->direction == ord2->direction)
return CMP_EQ;
return ord1->direction > ord2->direction ? CMP_GT : CMP_LT;
}
else
return cmp > 0 ? CMP_GT : CMP_LT;
}
static
int compare_order_lists(SQL_I_List<ORDER> *part_list1,
SQL_I_List<ORDER> *part_list2)
{
if (part_list1 == part_list2)
return CMP_EQ;
ORDER *elem1= part_list1->first;
ORDER *elem2= part_list2->first;
for ( ; elem1 && elem2; elem1= elem1->next, elem2= elem2->next)
{
int cmp;
if ((cmp= compare_order_elements(elem1, elem2)))
return cmp;
}
if (elem1)
return CMP_GT_C;
if (elem2)
return CMP_LT_C;
return CMP_EQ;
}
static
int compare_window_frame_bounds(Window_frame_bound *win_frame_bound1,
Window_frame_bound *win_frame_bound2,
bool is_bottom_bound)
{
int res;
if (win_frame_bound1->precedence_type != win_frame_bound2->precedence_type)
{
res= win_frame_bound1->precedence_type > win_frame_bound2->precedence_type ?
CMP_GT : CMP_LT;
if (is_bottom_bound)
res= -res;
return res;
}
if (win_frame_bound1->is_unbounded() && win_frame_bound2->is_unbounded())
return CMP_EQ;
if (!win_frame_bound1->is_unbounded() && !win_frame_bound2->is_unbounded())
{
if (win_frame_bound1->offset->eq(win_frame_bound2->offset, true))
return CMP_EQ;
else
{
res= strcmp(win_frame_bound1->offset->name,
win_frame_bound2->offset->name);
res= res > 0 ? CMP_GT : CMP_LT;
if (is_bottom_bound)
res= -res;
return res;
}
}
/*
Here we have:
win_frame_bound1->is_unbounded() != win_frame_bound1->is_unbounded()
*/
return is_bottom_bound != win_frame_bound1->is_unbounded() ? CMP_LT : CMP_GT;
}
static
int compare_window_frames(Window_frame *win_frame1,
Window_frame *win_frame2)
{
int cmp;
if (win_frame1 == win_frame2)
return CMP_EQ;
if (!win_frame1)
return CMP_LT;
if (!win_frame2)
return CMP_GT;
if (win_frame1->units != win_frame2->units)
return win_frame1->units > win_frame2->units ? CMP_GT : CMP_LT;
cmp= compare_window_frame_bounds(win_frame1->top_bound,
win_frame2->top_bound,
false);
if (cmp)
return cmp;
cmp= compare_window_frame_bounds(win_frame1->bottom_bound,
win_frame2->bottom_bound,
true);
if (cmp)
return cmp;
if (win_frame1->exclusion != win_frame2->exclusion)
return win_frame1->exclusion > win_frame2->exclusion ? CMP_GT_C : CMP_LT_C;
return CMP_EQ;
}
static
int compare_window_spec_joined_lists(Window_spec *win_spec1,
Window_spec *win_spec2)
{
win_spec1->join_partition_and_order_lists();
win_spec2->join_partition_and_order_lists();
int cmp= compare_order_lists(win_spec1->partition_list,
win_spec2->partition_list);
win_spec1->disjoin_partition_and_order_lists();
win_spec2->disjoin_partition_and_order_lists();
return cmp;
}
static
int compare_window_funcs_by_window_specs(Item_window_func *win_func1,
Item_window_func *win_func2,
void *arg)
{
int cmp;
Window_spec *win_spec1= win_func1->window_spec;
Window_spec *win_spec2= win_func2->window_spec;
if (win_spec1 == win_spec2)
return CMP_EQ;
cmp= compare_order_lists(win_spec1->partition_list,
win_spec2->partition_list);
if (cmp == CMP_EQ)
{
/*
Partition lists contain the same elements.
Let's use only one of the lists.
*/
if (!win_spec1->name() && win_spec2->name())
win_spec1->partition_list= win_spec2->partition_list;
else
win_spec2->partition_list= win_spec1->partition_list;
cmp= compare_order_lists(win_spec1->order_list,
win_spec2->order_list);
if (cmp != CMP_EQ)
return cmp;
/*
Order lists contain the same elements.
Let's use only one of the lists.
*/
if (!win_spec1->name() && win_spec2->name())
win_spec1->order_list= win_spec2->order_list;
else
win_spec2->order_list= win_spec1->order_list;
cmp= compare_window_frames(win_spec1->window_frame,
win_spec2->window_frame);
if (cmp != CMP_EQ)
return cmp;
/* Window frames are equal. Let's use only one of them. */
if (!win_spec1->name() && win_spec2->name())
win_spec1->window_frame= win_spec2->window_frame;
else
win_spec2->window_frame= win_spec1->window_frame;
return CMP_EQ;
}
if (cmp == CMP_GT || cmp == CMP_LT)
return cmp;
/* one of the partitions lists is the proper beginning of the another */
cmp= compare_window_spec_joined_lists(win_spec1, win_spec2);
if (CMP_LT_C <= cmp && cmp <= CMP_GT_C)
cmp= win_spec1->partition_list->elements <
win_spec2->partition_list->elements ? CMP_GT_C : CMP_LT_C;
return cmp;
}
#define SORTORDER_CHANGE_FLAG 1
#define PARTITION_CHANGE_FLAG 2
#define FRAME_CHANGE_FLAG 4
typedef int (*Item_window_func_cmp)(Item_window_func *f1,
Item_window_func *f2,
void *arg);
/*
@brief
Sort window functions so that those that can be computed together are
adjacent.
@detail
Sort window functions by their
- required sorting order,
- partition list,
- window frame compatibility.
The changes between the groups are marked by setting item_window_func->marker.
*/
static
void order_window_funcs_by_window_specs(List<Item_window_func> *win_func_list)
{
if (win_func_list->elements == 0)
return;
bubble_sort<Item_window_func>(win_func_list,
compare_window_funcs_by_window_specs,
NULL);
List_iterator_fast<Item_window_func> it(*win_func_list);
Item_window_func *prev= it++;
prev->marker= SORTORDER_CHANGE_FLAG |
PARTITION_CHANGE_FLAG |
FRAME_CHANGE_FLAG;
Item_window_func *curr;
while ((curr= it++))
{
Window_spec *win_spec_prev= prev->window_spec;
Window_spec *win_spec_curr= curr->window_spec;
curr->marker= 0;
if (!(win_spec_prev->partition_list == win_spec_curr->partition_list &&
win_spec_prev->order_list == win_spec_curr->order_list))
{
int cmp;
if (win_spec_prev->partition_list == win_spec_curr->partition_list)
cmp= compare_order_lists(win_spec_prev->order_list,
win_spec_curr->order_list);
else
cmp= compare_window_spec_joined_lists(win_spec_prev, win_spec_curr);
if (!(CMP_LT_C <= cmp && cmp <= CMP_GT_C))
{
curr->marker= SORTORDER_CHANGE_FLAG |
PARTITION_CHANGE_FLAG |
FRAME_CHANGE_FLAG;
}
else if (win_spec_prev->partition_list != win_spec_curr->partition_list)
{
curr->marker|= PARTITION_CHANGE_FLAG | FRAME_CHANGE_FLAG;
}
}
else if (win_spec_prev->window_frame != win_spec_curr->window_frame)
curr->marker|= FRAME_CHANGE_FLAG;
prev= curr;
}
}
/////////////////////////////////////////////////////////////////////////////
/*
Do a pass over sorted table and compute window function values.
This function is for handling window functions that can be computed on the
fly. Examples are RANK() and ROW_NUMBER().
*/
bool compute_window_func_values(Item_window_func *item_win,
TABLE *tbl, READ_RECORD *info)
{
int err;
while (!(err=info->read_record(info)))
{
store_record(tbl,record[1]);
/*
This will cause window function to compute its value for the
current row :
*/
item_win->advance_window();
/*
Put the new value into temptable's field
TODO: Should this use item_win->update_field() call?
Regular aggegate function implementations seem to implement it.
*/
item_win->save_in_field(item_win->result_field, true);
err= tbl->file->ha_update_row(tbl->record[1], tbl->record[0]);
if (err && err != HA_ERR_RECORD_IS_THE_SAME)
return true;
}
return false;
}
/////////////////////////////////////////////////////////////////////////////
// Window Frames support
/////////////////////////////////////////////////////////////////////////////
// note: make rr_from_pointers static again when not need it here anymore
int rr_from_pointers(READ_RECORD *info);
/*
A temporary way to clone READ_RECORD structures until Monty provides the real
one.
*/
bool clone_read_record(const READ_RECORD *src, READ_RECORD *dst)
{
//DBUG_ASSERT(src->table->sort.record_pointers);
DBUG_ASSERT(src->read_record == rr_from_pointers);
memcpy(dst, src, sizeof(READ_RECORD));
return false;
}
/////////////////////////////////////////////////////////////////////////////
/*
A cursor over a sequence of rowids. One can
- Move to next rowid
- jump to given number in the sequence
- Know the number of the current rowid (i.e. how many rowids have been read)
*/
class Rowid_seq_cursor
{
uchar *cache_start;
uchar *cache_pos;
uchar *cache_end;
uint ref_length;
public:
virtual ~Rowid_seq_cursor() {}
void init(READ_RECORD *info)
{
cache_start= info->cache_pos;
cache_pos= info->cache_pos;
cache_end= info->cache_end;
ref_length= info->ref_length;
}
virtual int get_next()
{
/* Allow multiple get_next() calls in EOF state*/
if (cache_pos == cache_end)
return -1;
cache_pos+= ref_length;
return 0;
}
ha_rows get_rownum()
{
return (cache_pos - cache_start) / ref_length;
}
// will be called by ROWS n FOLLOWING to catch up.
void move_to(ha_rows row_number)
{
cache_pos= cache_start + row_number * ref_length;
}
protected:
bool at_eof() { return (cache_pos == cache_end); }
uchar *get_last_rowid()
{
if (cache_pos == cache_start)
return NULL;
else
return cache_pos - ref_length;
}
uchar *get_curr_rowid() { return cache_pos; }
};
/*
Cursor which reads from rowid sequence and also retrieves table rows.
*/
class Table_read_cursor : public Rowid_seq_cursor
{
/*
Note: we don't own *read_record, somebody else is using it.
We only look at the constant part of it, e.g. table, record buffer, etc.
*/
READ_RECORD *read_record;
public:
virtual ~Table_read_cursor() {}
void init(READ_RECORD *info)
{
Rowid_seq_cursor::init(info);
read_record= info;
}
virtual int get_next()
{
if (at_eof())
return -1;
uchar* curr_rowid= get_curr_rowid();
int res= Rowid_seq_cursor::get_next();
if (!res)
{
res= read_record->table->file->ha_rnd_pos(read_record->record,
curr_rowid);
}
return res;
}
bool restore_last_row()
{
uchar *p;
if ((p= get_last_rowid()))
{
int rc= read_record->table->file->ha_rnd_pos(read_record->record, p);
if (!rc)
return true; // restored ok
}
return false; // didn't restore
}
// todo: should move_to() also read row here?
};
/*
A cursor which only moves within a partition. The scan stops at the partition
end, and it needs an explicit command to move to the next partition.
*/
class Partition_read_cursor
{
Table_read_cursor tbl_cursor;
Group_bound_tracker bound_tracker;
bool end_of_partition;
public:
void init(THD *thd, READ_RECORD *info, SQL_I_List<ORDER> *partition_list)
{
tbl_cursor.init(info);
bound_tracker.init(thd, partition_list);
end_of_partition= false;
}
/*
Informs the cursor that we need to move into the next partition.
The next partition is provided in two ways:
- in table->record[0]..
- rownum parameter has the row number.
*/
void on_next_partition(int rownum)
{
/* Remember the sort key value from the new partition */
bound_tracker.check_if_next_group();
end_of_partition= false;
}
/*
Moves to a new row. The row is assumed to be within the current partition
*/
void move_to(int rownum) { tbl_cursor.move_to(rownum); }
/*
This returns -1 when end of partition was reached.
*/
int get_next()
{
int res;
if (end_of_partition)
return -1;
if ((res= tbl_cursor.get_next()))
return res;
if (bound_tracker.compare_with_cache())
{
end_of_partition= true;
return -1;
}
return 0;
}
bool restore_last_row()
{
return tbl_cursor.restore_last_row();
}
};
/////////////////////////////////////////////////////////////////////////////
/*
Window frame bound cursor. Abstract interface.
@detail
The cursor moves within the partition that the current row is in.
It may be ahead or behind the current row.
The cursor also assumes that the current row moves forward through the
partition and will move to the next adjacent partition after this one.
List of all cursor classes:
Frame_cursor
Frame_range_n_top
Frame_range_n_bottom
Frame_range_current_row_top
Frame_range_current_row_bottom
Frame_n_rows_preceding
Frame_n_rows_following
Frame_rows_current_row_top = Frame_n_rows_preceding(0)
Frame_rows_current_row_bottom
// These handle both RANGE and ROWS-type bounds
Frame_unbounded_preceding
Frame_unbounded_following
// This is not used as a frame bound, it counts rows in the partition:
Frame_unbounded_following_set_count : public Frame_unbounded_following
@todo
- if we want to allocate this on the MEM_ROOT we should make sure
it is not re-allocated for every subquery execution.
*/
class Frame_cursor : public Sql_alloc
{
public:
virtual void init(THD *thd, READ_RECORD *info,
SQL_I_List<ORDER> *partition_list,
SQL_I_List<ORDER> *order_list)
{}
/*
Current row has moved to the next partition and is positioned on the first
row there. Position the frame bound accordingly.
@param first - TRUE means this is the first partition
@param item - Put or remove rows from there.
@detail
- if first==false, the caller guarantees that tbl->record[0] points at the
first row in the new partition.
- if first==true, we are just starting in the first partition and no such
guarantee is provided.
- The callee may move tbl->file and tbl->record[0] to point to some other
row.
*/
virtual void pre_next_partition(longlong rownum, Item_sum* item){};
virtual void next_partition(longlong rownum, Item_sum* item)=0;
/*
The current row has moved one row forward.
Move this frame bound accordingly, and update the value of aggregate
function as necessary.
*/
virtual void pre_next_row(Item_sum* item){};
virtual void next_row(Item_sum* item)=0;
virtual ~Frame_cursor(){}
};
//////////////////////////////////////////////////////////////////////////////
// RANGE-type frames
//////////////////////////////////////////////////////////////////////////////
/*
Frame_range_n_top handles the top end of RANGE-type frame.
That is, it handles:
RANGE BETWEEN n PRECEDING AND ...
RANGE BETWEEN n FOLLOWING AND ...
Top of the frame doesn't need to check for partition end, since bottom will
reach it before.
*/
class Frame_range_n_top : public Frame_cursor
{
Table_read_cursor cursor;
Cached_item_item *range_expr;
Item *n_val;
Item *item_add;
const bool is_preceding;
/*
1 when order_list uses ASC ordering
-1 when order_list uses DESC ordering
*/
int order_direction;
public:
Frame_range_n_top(bool is_preceding_arg, Item *n_val_arg) :
n_val(n_val_arg), item_add(NULL), is_preceding(is_preceding_arg)
{}
void init(THD *thd, READ_RECORD *info,
SQL_I_List<ORDER> *partition_list,
SQL_I_List<ORDER> *order_list)
{
cursor.init(info);
DBUG_ASSERT(order_list->elements == 1);
Item *src_expr= order_list->first->item[0];
if (order_list->first->direction == ORDER::ORDER_ASC)
order_direction= 1;
else
order_direction= -1;
range_expr= (Cached_item_item*) new_Cached_item(thd, src_expr, FALSE);
bool use_minus= is_preceding;
if (order_direction == -1)
use_minus= !use_minus;
if (use_minus)
item_add= new (thd->mem_root) Item_func_minus(thd, src_expr, n_val);
else
item_add= new (thd->mem_root) Item_func_plus(thd, src_expr, n_val);
item_add->fix_fields(thd, &item_add);
}
void pre_next_partition(longlong rownum, Item_sum* item)
{
// Save the value of FUNC(current_row)
range_expr->fetch_value_from(item_add);
}
void next_partition(longlong rownum, Item_sum* item)
{
cursor.move_to(rownum);
walk_till_non_peer(item);
}
void pre_next_row(Item_sum* item)
{
range_expr->fetch_value_from(item_add);
}
void next_row(Item_sum* item)
{
/*
Ok, our cursor is at the first row R where
(prev_row + n) >= R
We need to check about the current row.
*/
if (cursor.restore_last_row())
{
if (order_direction * range_expr->cmp_read_only() <= 0)
return;
item->remove();
}
walk_till_non_peer(item);
}
private:
void walk_till_non_peer(Item_sum* item)
{
while (!cursor.get_next())
{
if (order_direction * range_expr->cmp_read_only() <= 0)
break;
item->remove();
}
}
};
/*
Frame_range_n_bottom handles bottom end of RANGE-type frame.
That is, it handles frame bounds in form:
RANGE BETWEEN ... AND n PRECEDING
RANGE BETWEEN ... AND n FOLLOWING
Bottom end moves first so it needs to check for partition end
(todo: unless it's PRECEDING and in that case it doesnt)
(todo: factor out common parts with Frame_range_n_top into
a common ancestor)
*/
class Frame_range_n_bottom: public Frame_cursor
{
Partition_read_cursor cursor;
Cached_item_item *range_expr;
Item *n_val;
Item *item_add;
const bool is_preceding;
bool end_of_partition;
/*
1 when order_list uses ASC ordering
-1 when order_list uses DESC ordering
*/
int order_direction;
public:
Frame_range_n_bottom(bool is_preceding_arg, Item *n_val_arg) :
n_val(n_val_arg), item_add(NULL), is_preceding(is_preceding_arg)
{}
void init(THD *thd, READ_RECORD *info,
SQL_I_List<ORDER> *partition_list,
SQL_I_List<ORDER> *order_list)
{
cursor.init(thd, info, partition_list);
DBUG_ASSERT(order_list->elements == 1);
Item *src_expr= order_list->first->item[0];
if (order_list->first->direction == ORDER::ORDER_ASC)
order_direction= 1;
else
order_direction= -1;
range_expr= (Cached_item_item*) new_Cached_item(thd, src_expr, FALSE);
bool use_minus= is_preceding;
if (order_direction == -1)
use_minus= !use_minus;
if (use_minus)
item_add= new (thd->mem_root) Item_func_minus(thd, src_expr, n_val);
else
item_add= new (thd->mem_root) Item_func_plus(thd, src_expr, n_val);
item_add->fix_fields(thd, &item_add);
}
void pre_next_partition(longlong rownum, Item_sum* item)
{
// Save the value of FUNC(current_row)
range_expr->fetch_value_from(item_add);
cursor.on_next_partition(rownum);
end_of_partition= false;
}
void next_partition(longlong rownum, Item_sum* item)
{
cursor.move_to(rownum);
walk_till_non_peer(item);
}
void pre_next_row(Item_sum* item)
{
if (end_of_partition)
return;
range_expr->fetch_value_from(item_add);
}
void next_row(Item_sum* item)
{
if (end_of_partition)
return;
/*
Ok, our cursor is at the first row R where
(prev_row + n) >= R
We need to check about the current row.
*/
if (cursor.restore_last_row())
{
if (order_direction * range_expr->cmp_read_only() < 0)
return;
item->add();
}
walk_till_non_peer(item);
}
private:
void walk_till_non_peer(Item_sum* item)
{
int res;
while (!(res= cursor.get_next()))
{
if (order_direction * range_expr->cmp_read_only() < 0)
break;
item->add();
}
if (res)
end_of_partition= true;
}
};
/*
RANGE BETWEEN ... AND CURRENT ROW, bottom frame bound for CURRENT ROW
...
| peer1
| peer2 <----- current_row
| peer3
+-peer4 <----- the cursor points here. peer4 itself is included.
nonpeer1
nonpeer2
This bound moves in front of the current_row. It should be a the first row
that is still a peer of the current row.
*/
class Frame_range_current_row_bottom: public Frame_cursor
{
Partition_read_cursor cursor;
Group_bound_tracker peer_tracker;
bool dont_move;
public:
void init(THD *thd, READ_RECORD *info,
SQL_I_List<ORDER> *partition_list,
SQL_I_List<ORDER> *order_list)
{
cursor.init(thd, info, partition_list);
peer_tracker.init(thd, order_list);
}
void pre_next_partition(longlong rownum, Item_sum* item)
{
// Save the value of the current_row
peer_tracker.check_if_next_group();
cursor.on_next_partition(rownum);
if (rownum != 0)
{
// Add the current row now because our cursor has already seen it
item->add();
}
}
void next_partition(longlong rownum, Item_sum* item)
{
walk_till_non_peer(item);
}
void pre_next_row(Item_sum* item)
{
dont_move= !peer_tracker.check_if_next_group();
if (!dont_move)
item->add();
}
void next_row(Item_sum* item)
{
// Check if our cursor is pointing at a peer of the current row.
// If not, move forward until that becomes true
if (dont_move)
{
/*
Our current is not a peer of the current row.
No need to move the bound.
*/
return;
}
walk_till_non_peer(item);
}
private:
void walk_till_non_peer(Item_sum* item)
{
/*
Walk forward until we've met first row that's not a peer of the current
row
*/
while (!cursor.get_next())
{
if (peer_tracker.compare_with_cache())
break;
item->add();
}
}
};
/*
RANGE BETWEEN CURRENT ROW AND .... Top CURRENT ROW, RANGE-type frame bound
nonpeer1
nonpeer2
+-peer1 <----- the cursor points here. peer1 itself is included.
| peer2
| peer3 <----- current_row
| peer4
...
It moves behind the current_row. It is located right after the first peer of
the current_row.
*/
class Frame_range_current_row_top : public Frame_cursor
{
Group_bound_tracker bound_tracker;
Table_read_cursor cursor;
Group_bound_tracker peer_tracker;
bool move;
public:
void init(THD *thd, READ_RECORD *info,
SQL_I_List<ORDER> *partition_list,
SQL_I_List<ORDER> *order_list)
{
bound_tracker.init(thd, partition_list);
cursor.init(info);
peer_tracker.init(thd, order_list);
}
void pre_next_partition(longlong rownum, Item_sum* item)
{
// Fetch the value from the first row
peer_tracker.check_if_next_group();
cursor.move_to(rownum+1);
}
void next_partition(longlong rownum, Item_sum* item) {}
void pre_next_row(Item_sum* item)
{
// Check if the new current_row is a peer of the row that our cursor is
// pointing to.
move= peer_tracker.check_if_next_group();
}
void next_row(Item_sum* item)
{
if (move)
{
/*
Our cursor is pointing at the first row that was a peer of the previous
current row. Or, it was the first row in the partition.
*/
if (cursor.restore_last_row())
{
// todo: need the following check ?
if (!peer_tracker.compare_with_cache())
return;
item->remove();
}
do
{
if (cursor.get_next())
return;
if (!peer_tracker.compare_with_cache())
return;
item->remove();
}
while (1);
}
}
};
/////////////////////////////////////////////////////////////////////////////
// UNBOUNDED frame bounds (shared between RANGE and ROWS)
/////////////////////////////////////////////////////////////////////////////
/*
UNBOUNDED PRECEDING frame bound
*/
class Frame_unbounded_preceding : public Frame_cursor
{
public:
void next_partition(longlong rownum, Item_sum* item)
{
/*
UNBOUNDED PRECEDING frame end just stays on the first row.
We are top of the frame, so we don't need to update the sum function.
*/
}
void next_row(Item_sum* item)
{
/* Do nothing, UNBOUNDED PRECEDING frame end doesn't move. */
}
};
/*
UNBOUNDED FOLLOWING frame bound
*/
class Frame_unbounded_following : public Frame_cursor
{
protected:
Partition_read_cursor cursor;
public:
void init(THD *thd, READ_RECORD *info, SQL_I_List<ORDER> *partition_list,
SQL_I_List<ORDER> *order_list)
{
cursor.init(thd, info, partition_list);
}
void pre_next_partition(longlong rownum, Item_sum* item)
{
cursor.on_next_partition(rownum);
}
void next_partition(longlong rownum, Item_sum* item)
{
if (!rownum)
{
/* Read the first row */
if (cursor.get_next())
return;
}
item->add();
/* Walk to the end of the partition, updating the SUM function */
while (!cursor.get_next())
{
item->add();
}
}
void next_row(Item_sum* item)
{
/* Do nothing, UNBOUNDED FOLLOWING frame end doesn't move */
}
};
class Frame_unbounded_following_set_count : public Frame_unbounded_following
{
public:
// pre_next_partition is inherited
void next_partition(longlong rownum, Item_sum* item)
{
ulonglong num_rows_in_partition= 0;
if (!rownum)
{
/* Read the first row */
if (cursor.get_next())
return;
}
num_rows_in_partition++;
/* Walk to the end of the partition, find how many rows there are. */
while (!cursor.get_next())
{
num_rows_in_partition++;
}
Item_sum_window_with_row_count* item_with_row_count =
static_cast<Item_sum_window_with_row_count *>(item);
item_with_row_count->set_row_count(num_rows_in_partition);
}
};
/////////////////////////////////////////////////////////////////////////////
// ROWS-type frame bounds
/////////////////////////////////////////////////////////////////////////////
/*
ROWS $n PRECEDING frame bound
*/
class Frame_n_rows_preceding : public Frame_cursor
{
/* Whether this is top of the frame or bottom */
const bool is_top_bound;
const ha_rows n_rows;
/* Number of rows that we need to skip before our cursor starts moving */
ha_rows n_rows_to_skip;
Table_read_cursor cursor;
public:
Frame_n_rows_preceding(bool is_top_bound_arg, ha_rows n_rows_arg) :
is_top_bound(is_top_bound_arg), n_rows(n_rows_arg)
{}
void init(THD *thd, READ_RECORD *info, SQL_I_List<ORDER> *partition_list,
SQL_I_List<ORDER> *order_list)
{
cursor.init(info);
}
void next_partition(longlong rownum, Item_sum* item)
{
/*
Position our cursor to point at the first row in the new partition
(for rownum=0, it is already there, otherwise, it lags behind)
*/
if (rownum != 0)
cursor.move_to(rownum);
/*
Suppose the bound is ROWS 2 PRECEDING, and current row is row#n:
...
n-3
n-2 --- bound row
n-1
n --- current_row
...
The bound should point at row #(n-2). Bounds are inclusive, so
- bottom bound should add row #(n-2) into the window function
- top bound should remove row (#n-3) from the window function.
*/
n_rows_to_skip= n_rows + (is_top_bound? 1:0) - 1;
/* Bottom bound "ROWS 0 PRECEDING" is a special case: */
if (n_rows_to_skip == ha_rows(-1))
{
cursor.get_next();
item->add();
n_rows_to_skip= 0;
}
}
void next_row(Item_sum* item)
{
if (n_rows_to_skip)
{
n_rows_to_skip--;
return;
}
if (cursor.get_next())
return; // this is not expected to happen.
if (is_top_bound) // this is frame start endpoint
item->remove();
else
item->add();
}
};
/*
ROWS ... CURRENT ROW, Bottom bound.
This case is moved to separate class because here we don't need to maintain
our own cursor, or check for partition bound.
*/
class Frame_rows_current_row_bottom : public Frame_cursor
{
public:
void pre_next_partition(longlong rownum, Item_sum* item)
{
item->add();
}
void next_partition(longlong rownum, Item_sum* item) {}
void pre_next_row(Item_sum* item)
{
/* Temp table's current row is current_row. Add it to the window func */
item->add();
}
void next_row(Item_sum* item) {};
};
/*
ROWS-type CURRENT ROW, top bound.
This serves for processing "ROWS BETWEEN CURRENT ROW AND ..." frames.
n-1
n --+ --- current_row, and top frame bound
n+1 |
... |
when the current_row moves to row #n, this frame bound should remove the
row #(n-1) from the window function.
In other words, we need what "ROWS PRECEDING 0" provides.
*/
class Frame_rows_current_row_top: public Frame_n_rows_preceding
{
public:
Frame_rows_current_row_top() :
Frame_n_rows_preceding(true /*top*/, 0 /* n_rows */)
{}
};
/*
ROWS $n FOLLOWING frame bound.
*/
class Frame_n_rows_following : public Frame_cursor
{
/* Whether this is top of the frame or bottom */
const bool is_top_bound;
const ha_rows n_rows;
Partition_read_cursor cursor;
bool at_partition_end;
public:
Frame_n_rows_following(bool is_top_bound_arg, ha_rows n_rows_arg) :
is_top_bound(is_top_bound_arg), n_rows(n_rows_arg)
{
DBUG_ASSERT(n_rows > 0);
}
void init(THD *thd, READ_RECORD *info, SQL_I_List<ORDER> *partition_list,
SQL_I_List<ORDER> *order_list)
{
cursor.init(thd, info, partition_list);
at_partition_end= false;
}
void pre_next_partition(longlong rownum, Item_sum* item)
{
at_partition_end= false;
cursor.on_next_partition(rownum);
if (rownum != 0)
{
// This is only needed for "FOLLOWING 1". It is one row behind
cursor.move_to(rownum+1);
// Current row points at the first row in the partition
if (is_top_bound) // this is frame top endpoint
item->remove();
else
item->add();
}
}
/* Move our cursor to be n_rows ahead. */
void next_partition(longlong rownum, Item_sum* item)
{
longlong i_end= n_rows + ((rownum==0)?1:0)- is_top_bound;
for (longlong i= 0; i < i_end; i++)
{
if (next_row_intern(item))
break;
}
}
void next_row(Item_sum* item)
{
if (at_partition_end)
return;
next_row_intern(item);
}
private:
bool next_row_intern(Item_sum *item)
{
if (!cursor.get_next())
{
if (is_top_bound) // this is frame start endpoint
item->remove();
else
item->add();
}
else
at_partition_end= true;
return at_partition_end;
}
};
/*
Get a Frame_cursor for a frame bound. This is a "factory function".
*/
Frame_cursor *get_frame_cursor(Window_frame *frame, bool is_top_bound)
{
if (!frame)
{
/*
The docs say this about the lack of frame clause:
Let WD be a window structure descriptor.
...
If WD has no window framing clause, then
Case:
i) If the window ordering clause of WD is not present, then WF is the
window partition of R.
ii) Otherwise, WF consists of all rows of the partition of R that
precede R or are peers of R in the window ordering of the window
partition defined by the window ordering clause.
For case #ii, the frame bounds essentially are "RANGE BETWEEN UNBOUNDED
PRECEDING AND CURRENT ROW".
For the case #i, without ordering clause all rows are considered peers,
so again the same frame bounds can be used.
*/
if (is_top_bound)
return new Frame_unbounded_preceding;
else
return new Frame_range_current_row_bottom;
}
Window_frame_bound *bound= is_top_bound? frame->top_bound :
frame->bottom_bound;
if (bound->precedence_type == Window_frame_bound::PRECEDING ||
bound->precedence_type == Window_frame_bound::FOLLOWING)
{
bool is_preceding= (bound->precedence_type ==
Window_frame_bound::PRECEDING);
if (bound->offset == NULL) /* this is UNBOUNDED */
{
/* The following serve both RANGE and ROWS: */
if (is_preceding)
return new Frame_unbounded_preceding;
else
return new Frame_unbounded_following;
}
if (frame->units == Window_frame::UNITS_ROWS)
{
longlong n_rows= bound->offset->val_int();
/* These should be handled in the parser */
DBUG_ASSERT(!bound->offset->null_value);
DBUG_ASSERT(n_rows >= 0);
if (is_preceding)
return new Frame_n_rows_preceding(is_top_bound, n_rows);
else
return new Frame_n_rows_following(is_top_bound, n_rows);
}
else
{
if (is_top_bound)
return new Frame_range_n_top(is_preceding, bound->offset);
else
return new Frame_range_n_bottom(is_preceding, bound->offset);
}
}
if (bound->precedence_type == Window_frame_bound::CURRENT)
{
if (frame->units == Window_frame::UNITS_ROWS)
{
if (is_top_bound)
return new Frame_rows_current_row_top;
else
return new Frame_rows_current_row_bottom;
}
else
{
if (is_top_bound)
return new Frame_range_current_row_top;
else
return new Frame_range_current_row_bottom;
}
}
return NULL;
}
void add_extra_frame_cursors(List<Frame_cursor> *cursors,
const Item_sum *window_func)
{
switch (window_func->sum_func())
{
case Item_sum::CUME_DIST_FUNC:
cursors->push_back(new Frame_unbounded_preceding);
cursors->push_back(new Frame_range_current_row_bottom);
break;
default:
cursors->push_back(new Frame_unbounded_preceding);
cursors->push_back(new Frame_rows_current_row_bottom);
}
}
void get_window_func_required_cursors(
List<Frame_cursor> *result, const Item_window_func* item_win)
{
if (item_win->requires_partition_size())
result->push_back(new Frame_unbounded_following_set_count);
/*
If it is not a regular window function that follows frame specifications,
specific cursors are required.
*/
if (item_win->is_frame_prohibited())
{
add_extra_frame_cursors(result, item_win->window_func());
return;
}
/* A regular window function follows the frame specification. */
result->push_back(get_frame_cursor(item_win->window_spec->window_frame,
false));
result->push_back(get_frame_cursor(item_win->window_spec->window_frame,
true));
}
/*
Streamed window function computation with window frames.
We make a single pass over the ordered temp.table, but we're using three
cursors:
- current row - the row that we're computing window func value for)
- start_bound - the start of the frame
- bottom_bound - the end of the frame
All three cursors move together.
@todo
Provided bounds have their 'cursors'... is it better to re-clone their
cursors or re-position them onto the current row?
@detail
ROWS BETWEEN 3 PRECEDING -- frame start
AND 3 FOLLOWING -- frame end
/------ frame end (aka BOTTOM)
Dataset start |
--------====*=======[*]========*========-------->> dataset end
| \
| +-------- current row
|
\-------- frame start ("TOP")
- frame_end moves forward and adds rows into the aggregate function.
- frame_start follows behind and removes rows from the aggregate function.
- current_row is the row where the value of aggregate function is stored.
@TODO: Only the first cursor needs to check for run-out-of-partition
condition (Others can catch up by counting rows?)
*/
bool compute_window_func_with_frames(Item_window_func *item_win,
TABLE *tbl, READ_RECORD *info)
{
THD *thd= current_thd;
int err= 0;
Item_sum *sum_func= item_win->window_func();
/* This algorithm doesn't support DISTINCT aggregator */
sum_func->set_aggregator(Aggregator::SIMPLE_AGGREGATOR);
List<Frame_cursor> cursors;
get_window_func_required_cursors(&cursors, item_win);
List_iterator_fast<Frame_cursor> it(cursors);
Frame_cursor *c;
while((c= it++))
{
c->init(thd, info, item_win->window_spec->partition_list,
item_win->window_spec->order_list);
}
bool is_error= false;
longlong rownum= 0;
uchar *rowid_buf= (uchar*) my_malloc(tbl->file->ref_length, MYF(0));
while (true)
{
/* Move the current_row */
if ((err=info->read_record(info)))
{
break; /* End of file */
}
bool partition_changed= item_win->check_if_partition_changed();
tbl->file->position(tbl->record[0]);
memcpy(rowid_buf, tbl->file->ref, tbl->file->ref_length);
if (partition_changed || (rownum == 0))
{
sum_func->clear();
/*
pre_XXX functions assume that tbl->record[0] contains current_row, and
they may not change it.
*/
it.rewind();
while ((c= it++))
c->pre_next_partition(rownum, sum_func);
/*
We move bottom_bound first, because we want rows to be added into the
aggregate before top_bound attempts to remove them.
*/
it.rewind();
while ((c= it++))
c->next_partition(rownum, sum_func);
}
else
{
/* Again, both pre_XXX function can find current_row in tbl->record[0] */
it.rewind();
while ((c= it++))
c->pre_next_row(sum_func);
/* These make no assumptions about tbl->record[0] and may change it */
it.rewind();
while ((c= it++))
c->next_row(sum_func);
}
rownum++;
/*
Frame cursors may have made tbl->record[0] to point to some record other
than current_row. This applies to tbl->file's internal state, too.
Fix this by reading the current row again.
*/
tbl->file->ha_rnd_pos(tbl->record[0], rowid_buf);
store_record(tbl,record[1]);
item_win->save_in_field(item_win->result_field, true);
err= tbl->file->ha_update_row(tbl->record[1], tbl->record[0]);
if (err && err != HA_ERR_RECORD_IS_THE_SAME)
{
is_error= true;
break;
}
}
my_free(rowid_buf);
cursors.delete_elements();
return is_error? true: false;
}
/* Make a list that is a concation of two lists of ORDER elements */
static ORDER* concat_order_lists(MEM_ROOT *mem_root, ORDER *list1, ORDER *list2)
{
if (!list1)
{
list1= list2;
list2= NULL;
}
ORDER *res= NULL; // first element in the new list
ORDER *prev= NULL; // last element in the new list
ORDER *cur_list= list1; // this goes through list1, list2
while (cur_list)
{
for (ORDER *cur= cur_list; cur; cur= cur->next)
{
ORDER *copy= (ORDER*)alloc_root(mem_root, sizeof(ORDER));
memcpy(copy, cur, sizeof(ORDER));
if (prev)
prev->next= copy;
prev= copy;
if (!res)
res= copy;
}
cur_list= (cur_list == list1)? list2: NULL;
}
if (prev)
prev->next= NULL;
return res;
}
bool Window_func_runner::setup(THD *thd)
{
win_func->setup_partition_border_check(thd);
Item_sum::Sumfunctype type= win_func->window_func()->sum_func();
switch (type)
{
case Item_sum::ROW_NUMBER_FUNC:
case Item_sum::RANK_FUNC:
case Item_sum::DENSE_RANK_FUNC:
{
/*
One-pass window function computation, walk through the rows and
assign values.
*/
compute_func= compute_window_func_values;
break;
}
case Item_sum::COUNT_FUNC:
case Item_sum::SUM_BIT_FUNC:
case Item_sum::SUM_FUNC:
case Item_sum::AVG_FUNC:
case Item_sum::PERCENT_RANK_FUNC:
case Item_sum::CUME_DIST_FUNC:
case Item_sum::NTILE_FUNC:
{
/*
Frame-aware window function computation. It does one pass, but
uses three cursors -frame_start, current_row, and frame_end.
*/
compute_func= compute_window_func_with_frames;
break;
}
default:
my_error(ER_NOT_SUPPORTED_YET, MYF(0), "This aggregate as window function");
return true;
}
return false;
}
/*
Compute the value of window function for all rows.
*/
bool Window_func_runner::exec(TABLE *tbl, SORT_INFO *filesort_result)
{
THD *thd= current_thd;
win_func->set_phase_to_computation();
/* Go through the sorted array and compute the window function */
READ_RECORD info;
if (init_read_record(&info, thd, tbl, NULL/*select*/, filesort_result,
0, 1, FALSE))
return true;
bool is_error= compute_func(win_func, tbl, &info);
win_func->set_phase_to_retrieval();
end_read_record(&info);
return is_error;
}
bool Window_funcs_sort::exec(JOIN *join)
{
THD *thd= join->thd;
JOIN_TAB *join_tab= &join->join_tab[join->top_join_tab_count];
if (create_sort_index(thd, join, join_tab, filesort))
return true;
TABLE *tbl= join_tab->table;
SORT_INFO *filesort_result= join_tab->filesort_result;
bool is_error= false;
List_iterator<Window_func_runner> it(runners);
Window_func_runner *runner;
while ((runner= it++))
{
if ((is_error= runner->exec(tbl, filesort_result)))
break;
}
delete join_tab->filesort_result;
join_tab->filesort_result= NULL;
return is_error;
}
bool Window_funcs_sort::setup(THD *thd, SQL_SELECT *sel,
List_iterator<Item_window_func> &it)
{
Item_window_func *win_func= it.peek();
Item_window_func *prev_win_func;
do
{
Window_func_runner *runner;
if (!(runner= new Window_func_runner(win_func)) ||
runner->setup(thd))
{
return true;
}
runners.push_back(runner);
it++;
prev_win_func= win_func;
} while ((win_func= it.peek()) && !(win_func->marker & SORTORDER_CHANGE_FLAG));
/*
The sort criteria must be taken from the last win_func in the group of
adjacent win_funcs that do not have SORTORDER_CHANGE_FLAG.
*/
Window_spec *spec = prev_win_func->window_spec;
ORDER* sort_order= concat_order_lists(thd->mem_root,
spec->partition_list->first,
spec->order_list->first);
filesort= new (thd->mem_root) Filesort(sort_order, HA_POS_ERROR, true, NULL);
/* Apply the same condition that the subsequent sort has. */
filesort->select= sel;
return false;
}
bool Window_funcs_computation::setup(THD *thd,
List<Item_window_func> *window_funcs,
JOIN_TAB *tab)
{
order_window_funcs_by_window_specs(window_funcs);
SQL_SELECT *sel= NULL;
if (tab->filesort && tab->filesort->select)
{
sel= tab->filesort->select;
DBUG_ASSERT(!sel->quick);
}
Window_funcs_sort *srt;
List_iterator<Item_window_func> iter(*window_funcs);
while (iter.peek())
{
if (!(srt= new Window_funcs_sort()) ||
srt->setup(thd, sel, iter))
{
return true;
}
win_func_sorts.push_back(srt, thd->mem_root);
}
return false;
}
bool Window_funcs_computation::exec(JOIN *join)
{
List_iterator<Window_funcs_sort> it(win_func_sorts);
Window_funcs_sort *srt;
/* Execute each sort */
while ((srt = it++))
{
if (srt->exec(join))
return true;
}
return false;
}
void Window_funcs_computation::cleanup()
{
List_iterator<Window_funcs_sort> it(win_func_sorts);
Window_funcs_sort *srt;
while ((srt = it++))
{
srt->cleanup();
delete srt;
}
}
Explain_aggr_window_funcs*
Window_funcs_computation::save_explain_plan(MEM_ROOT *mem_root,
bool is_analyze)
{
Explain_aggr_window_funcs *xpl= new Explain_aggr_window_funcs;
List_iterator<Window_funcs_sort> it(win_func_sorts);
Window_funcs_sort *srt;
while ((srt = it++))
{
Explain_aggr_filesort *eaf=
new Explain_aggr_filesort(mem_root, is_analyze, srt->filesort);
xpl->sorts.push_back(eaf, mem_root);
}
return xpl;
}
/////////////////////////////////////////////////////////////////////////////
// Unneeded comments (will be removed when we develop a replacement for
// the feature that was attempted here
/////////////////////////////////////////////////////////////////////////////
/*
TODO Get this code to set can_compute_window_function during preparation,
not during execution.
The reason for this is the following:
Our single scan optimization for window functions without tmp table,
is valid, if and only if, we only need to perform one sorting operation,
via filesort. The cases where we need to perform one sorting operation only:
* A select with only one window function.
* A select with multiple window functions, but they must have their
partition and order by clauses compatible. This means that one ordering
is acceptable for both window functions.
For example:
partition by a, b, c; order by d, e results in sorting by a b c d e.
partition by a; order by d results in sorting by a d.
This kind of sorting is compatible. The less specific partition does
not care for the order of b and c columns so it is valid if we sort
by those in case of equality over a.
partition by a, b; order by d, e results in sorting by a b d e
partition by a; order by e results in sorting by a e
This sorting is incompatible due to the order by clause. The partition by
clause is compatible, (partition by a) is a prefix for (partition by a, b)
However, order by e is not a prefix for order by d, e, thus it is not
compatible.
The rule for having compatible sorting is thus:
Each partition order must contain the other window functions partitions
prefixes, or be a prefix itself. This must hold true for all partitions.
Analog for the order by clause.
*/
#if 0
List<Item_window_func> window_functions;
SQL_I_List<ORDER> largest_partition;
SQL_I_List<ORDER> largest_order_by;
bool can_compute_window_live = !need_tmp;
// Construct the window_functions item list and check if they can be
// computed using only one sorting.
//
// TODO: Perhaps group functions into compatible sorting bins
// to minimize the number of sorting passes required to compute all of them.
while ((item= it++))
{
if (item->type() == Item::WINDOW_FUNC_ITEM)
{
Item_window_func *item_win = (Item_window_func *) item;
window_functions.push_back(item_win);
if (!can_compute_window_live)
continue; // No point checking since we have to perform multiple sorts.
Window_spec *spec = item_win->window_spec;
// Having an empty partition list on one window function and a
// not empty list on a separate window function causes the sorting
// to be incompatible.
//
// Example:
// over (partition by a, order by x) && over (order by x).
//
// The first function requires an ordering by a first and then by x,
// while the seond function requires an ordering by x first.
// The same restriction is not required for the order by clause.
if (largest_partition.elements && !spec->partition_list.elements)
{
can_compute_window_live= FALSE;
continue;
}
can_compute_window_live= test_if_order_compatible(largest_partition,
spec->partition_list);
if (!can_compute_window_live)
continue;
can_compute_window_live= test_if_order_compatible(largest_order_by,
spec->order_list);
if (!can_compute_window_live)
continue;
if (largest_partition.elements < spec->partition_list.elements)
largest_partition = spec->partition_list;
if (largest_order_by.elements < spec->order_list.elements)
largest_order_by = spec->order_list;
}
}
if (can_compute_window_live && window_functions.elements && table_count == 1)
{
ha_rows examined_rows = 0;
ha_rows found_rows = 0;
ha_rows filesort_retval;
SORT_FIELD *s_order= (SORT_FIELD *) my_malloc(sizeof(SORT_FIELD) *
(largest_partition.elements + largest_order_by.elements) + 1,
MYF(MY_WME | MY_ZEROFILL | MY_THREAD_SPECIFIC));
size_t pos= 0;
for (ORDER* curr = largest_partition.first; curr; curr=curr->next, pos++)
s_order[pos].item = *curr->item;
for (ORDER* curr = largest_order_by.first; curr; curr=curr->next, pos++)
s_order[pos].item = *curr->item;
table[0]->sort.io_cache=(IO_CACHE*) my_malloc(sizeof(IO_CACHE),
MYF(MY_WME | MY_ZEROFILL|
MY_THREAD_SPECIFIC));
filesort_retval= filesort(thd, table[0], s_order,
(largest_partition.elements + largest_order_by.elements),
this->select, HA_POS_ERROR, FALSE,
&examined_rows, &found_rows,
this->explain->ops_tracker.report_sorting(thd));
table[0]->sort.found_records= filesort_retval;
join_tab->read_first_record = join_init_read_record;
join_tab->records= found_rows;
my_free(s_order);
}
else
#endif
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