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Bug#38918 selecting from information_schema.columns is disproportionately slow

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The problem: table_open_method is not calculated properly if '*' is used in 'select'
The fix: added table_open_method calculation for such case
This commit is contained in:
Sergey Glukhov
2008-10-09 12:50:29 +05:00
parent 8c6ffe3630
commit 973fb9962c
3 changed files with 28 additions and 1 deletions
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12
sql/sql_show.cc
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@ -2962,7 +2962,7 @@ static int fill_schema_table_names(THD *thd, TABLE *table,
@retval SKIP_OPEN_TABLE | OPEN_FRM_ONLY | OPEN_FULL_TABLE
*/
static uint get_table_open_method(TABLE_LIST *tables,
uint get_table_open_method(TABLE_LIST *tables,
ST_SCHEMA_TABLE *schema_table,
enum enum_schema_tables schema_table_idx)
{
@ -2973,12 +2973,22 @@ static uint get_table_open_method(TABLE_LIST *tables,
{
Field **ptr, *field;
int table_open_method= 0, field_indx= 0;
uint star_table_open_method= OPEN_FULL_TABLE;
bool used_star= true; // true if '*' is used in select
for (ptr=tables->table->field; (field= *ptr) ; ptr++)
{
star_table_open_method=
min(star_table_open_method,
schema_table->fields_info[field_indx].open_method);
if (bitmap_is_set(tables->table->read_set, field->field_index))
{
used_star= false;
table_open_method|= schema_table->fields_info[field_indx].open_method;
}
field_indx++;
}
if (used_star)
return star_table_open_method;
return table_open_method;
}
/* I_S tables which use get_all_tables but can not be optimized */