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Fix for Bug #3307 "FLUSH TABLES sometimes breaks prepared statement

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table resolution".
Added members to Item_ident for storing original db, table and field
names since those that set later from Field have shorter life-time 
than required by prep. stmt. So we need to restore original names in 
Item_ident::cleanup(). Also now using special construnctor for creation
of Item_field from Field object that ensures that table and field name 
have big enough life-time.

"Fix" for bug #2050 "10 to 1 performance drop with server 4.1.1"
Clean ups in implementation of caching of field number in table.
Added caching of table in which field is found in find_field_in_tables().
This commit is contained in:
dlenev@brandersnatch.localdomain
2004-03-31 21:25:55 +04:00
parent 9e28b7698d
commit 4122188cc2
5 changed files with 83 additions and 19 deletions
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47
sql/sql_base.cc
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@@ -1791,12 +1791,13 @@ bool rm_temporary_table(enum db_type base, char *path)
Field *find_field_in_table(THD *thd,TABLE *table,const char *name,uint length,
bool check_grants, bool allow_rowid,
int *cached_field_index_ptr)
uint *cached_field_index_ptr)
{
Field **field_ptr= 0, *field;
int cached_field_index= *cached_field_index_ptr;
Field **field_ptr, *field;
uint cached_field_index= *cached_field_index_ptr;
if (cached_field_index >= 0 && cached_field_index < table->fields &&
/* We assume here that table->field < NO_CACHED_FIELD_INDEX = UINT_MAX */
if (cached_field_index < table->fields &&
!my_strcasecmp(system_charset_info,
table->field[cached_field_index]->field_name, name))
field_ptr= table->field + cached_field_index;
@@ -1805,14 +1806,11 @@ Field *find_field_in_table(THD *thd,TABLE *table,const char *name,uint length,
length);
else
{
if (!(field_ptr=table->field))
if (!(field_ptr= table->field))
return (Field *)0;
while (*field_ptr)
{
for (; *field_ptr; ++field_ptr)
if (!my_strcasecmp(system_charset_info, (*field_ptr)->field_name, name))
break;
++field_ptr;
}
}
if (field_ptr && *field_ptr)
@@ -1882,6 +1880,31 @@ find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
uint length=(uint) strlen(name);
char name_buff[NAME_LEN+1];
if (item->cached_table)
{
/*
This shortcut is used by prepared statements. We assuming that
TABLE_LIST *tables is not changed during query execution (which
is true for all queries except RENAME but luckily RENAME doesn't
use fields...) so we can rely on reusing pointer to its member.
With this optimisation we also miss case when addition of one more
field makes some prepared query ambiguous and so erronous, but we
accept this trade off.
*/
found= find_field_in_table(thd,tables->table,name,length,
test(tables->table->grant.want_privilege),
1, &(item->cached_field_index));
if (found)
{
(*where)= tables;
if (found == WRONG_GRANT)
return (Field*) 0;
return found;
}
}
if (db && lower_case_table_names)
{
/*
@@ -1909,7 +1932,7 @@ find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
1, &(item->cached_field_index));
if (find)
{
(*where)= tables;
(*where)= item->cached_table= tables;
if (find == WRONG_GRANT)
return (Field*) 0;
if (db || !thd->where)
@@ -1968,7 +1991,7 @@ find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
{
if (field == WRONG_GRANT)
return (Field*) 0;
(*where)= tables;
(*where)= item->cached_table= tables;
if (found)
{
if (!thd->where) // Returns first found
@@ -2304,7 +2327,7 @@ insert_fields(THD *thd,TABLE_LIST *tables, const char *db_name,
thd->used_tables|=table->map;
while ((field = *ptr++))
{
Item_field *item= new Item_field(field);
Item_field *item= new Item_field(thd, field);
if (!found++)
(void) it->replace(item); // Replace '*'
else