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"Fix" for BUG #2050 "10 to 1 performance drop with server 4.1.1".

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Actually it is not a bug but right behavior observed as pefomance 
degradation after we have forced Item_field::fix_fields() to 
re-execute each time when we are executing prep stmt.

This patch implements small optimization which heals this bad 
behavior. We are caching field position in TABLE::field array in
Item's member and are using this position for speeding up field
lookups in fix_fields() in case of its re-execution.
This commit is contained in:
dlenev@brandersnatch.localdomain
2004-03-28 04:11:54 +04:00
parent b84a9dcf86
commit 9e28b7698d
8 changed files with 52 additions and 30 deletions
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55
sql/sql_base.cc
View File

@@ -1790,33 +1790,44 @@ bool rm_temporary_table(enum db_type base, char *path)
#define WRONG_GRANT (Field*) -1
Field *find_field_in_table(THD *thd,TABLE *table,const char *name,uint length,
bool check_grants, bool allow_rowid)
bool check_grants, bool allow_rowid,
int *cached_field_index_ptr)
{
Field *field;
if (table->name_hash.records)
Field **field_ptr= 0, *field;
int cached_field_index= *cached_field_index_ptr;
if (cached_field_index >= 0 && 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;
else if (table->name_hash.records)
field_ptr= (Field**)hash_search(&table->name_hash,(byte*) name,
length);
else
{
if ((field=(Field*) hash_search(&table->name_hash,(byte*) name,
length)))
goto found;
if (!(field_ptr=table->field))
return (Field *)0;
while (*field_ptr)
{
if (!my_strcasecmp(system_charset_info, (*field_ptr)->field_name, name))
break;
++field_ptr;
}
}
if (field_ptr && *field_ptr)
{
*cached_field_index_ptr= field_ptr - table->field;
field= *field_ptr;
}
else
{
Field **ptr;
if (!(ptr=table->field))
return (Field *)0;
while ((field = *ptr++))
{
if (!my_strcasecmp(system_charset_info, field->field_name, name))
goto found;
}
if (!allow_rowid ||
my_strcasecmp(system_charset_info, name, "_rowid") ||
!(field=table->rowid_field))
return (Field*) 0;
}
if (allow_rowid &&
!my_strcasecmp(system_charset_info, name, "_rowid") &&
(field=table->rowid_field))
goto found;
return (Field*) 0;
found:
if (thd->set_query_id)
{
if (field->query_id != thd->query_id)
@@ -1895,7 +1906,7 @@ find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
Field *find=find_field_in_table(thd,tables->table,name,length,
test(tables->table->grant.
want_privilege),
1);
1, &(item->cached_field_index));
if (find)
{
(*where)= tables;
@@ -1952,7 +1963,7 @@ find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
Field *field=find_field_in_table(thd,tables->table,name,length,
test(tables->table->grant.want_privilege),
allow_rowid);
allow_rowid, &(item->cached_field_index));
if (field)
{
if (field == WRONG_GRANT)