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ORDER BY optimization

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Fixed new bug when reading field types


client/mysql.cc:
  Fixed output for -T
libmysql/libmysql.c:
  Filled missing fields in new MYSQL_FIELD structure
  Fixed new bug when reading field types
mysql-test/r/order_by.result:
  Result after new order by optimization
sql/opt_range.cc:
  New ORDER BY optimization
sql/opt_range.h:
  New ORDER BY optimization
sql/set_var.cc:
  Speed optimization
sql/sql_select.cc:
  New ORDER BY optimization
  
  This alllows MySQL to change a ref/range index from (a,b) to (a,c) when 'b' was not used to find rows and one did
  ORDER BY a,c or ORDER BY c
This commit is contained in:
unknown
2003-05-27 18:40:37 +03:00
parent 1540912eca
commit ef6d3a8060
7 changed files with 40 additions and 20 deletions
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36
sql/sql_select.cc
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@ -6275,14 +6275,14 @@ is_subkey(KEY_PART_INFO *key_part, KEY_PART_INFO *ref_key_part,
*/
static uint
test_if_subkey(ORDER *order, TABLE *table, uint ref, key_map usable_keys)
test_if_subkey(ORDER *order, TABLE *table, uint ref, uint ref_key_parts,
key_map usable_keys)
{
uint nr;
uint min_length= (uint) ~0;
uint best= MAX_KEY;
uint not_used;
KEY_PART_INFO *ref_key_part= table->key_info[ref].key_part;
uint ref_key_parts= table->key_info[ref].key_parts;
KEY_PART_INFO *ref_key_part_end= ref_key_part + ref_key_parts;
for (nr= 0; usable_keys; usable_keys>>= 1, nr++)
@ -6317,10 +6317,12 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
bool no_changes)
{
int ref_key;
uint ref_key_parts;
TABLE *table=tab->table;
SQL_SELECT *select=tab->select;
key_map usable_keys;
DBUG_ENTER("test_if_skip_sort_order");
LINT_INIT(ref_key_parts);
/* Check which keys can be used to resolve ORDER BY */
usable_keys= ~(key_map) 0;
@ -6336,9 +6338,15 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
ref_key= -1;
if (tab->ref.key >= 0) // Constant range in WHERE
ref_key=tab->ref.key;
{
ref_key= tab->ref.key;
ref_key_parts= tab->ref.key_parts;
}
else if (select && select->quick) // Range found by opt_range
ref_key=select->quick->index;
{
ref_key= select->quick->index;
ref_key_parts= select->quick->used_key_parts;
}
if (ref_key >= 0)
{
@ -6352,20 +6360,28 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
/*
We come here when ref_key is not among usable_keys
*/
uint a;
if ((a= test_if_subkey(order, table, ref_key, usable_keys)) < MAX_KEY)
uint new_ref_key;
/*
If using index only read, only consider other possible index only
keys
*/
if (table->used_keys & (((key_map) 1 << ref_key)))
usable_keys|= table->used_keys;
if ((new_ref_key= test_if_subkey(order, table, ref_key, ref_key_parts,
usable_keys)) < MAX_KEY)
{
/* Found key that can be used to retrieve data in sorted order */
if (tab->ref.key >= 0)
{
tab->ref.key= a;
table->file->index_init(a);
tab->ref.key= new_ref_key;
table->file->index_init(new_ref_key);
}
else
{
select->quick->index= a;
select->quick->index= new_ref_key;
select->quick->init();
}
ref_key= a;
ref_key= new_ref_key;
}
}
/* Check if we get the rows in requested sorted order by using the key */