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Implementation of MDEV-28 LIMIT ROWS EXAMINED

Browse source 
https://mariadb.atlassian.net/browse/MDEV-28
  
This task implements a new clause LIMIT ROWS EXAMINED <num>
as an extention to the ANSI LIMIT clause. This extension
allows to limit the number of rows and/or keys a query
would access (read and/or write) during query execution.
This commit is contained in:
unknown 2012-03-11 14:39:20 +02:00
commit 8aebd44e0e
17 changed files with 1635 additions and 53 deletions
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25
sql/sql_union.cc
View file

@ -57,6 +57,8 @@ int select_union::send_data(List<Item> &values)
unit->offset_limit_cnt--;
return 0;
}
if (thd->killed == ABORT_QUERY)
return 0;
if (table->no_rows_with_nulls)
table->null_catch_flags= CHECK_ROW_FOR_NULLS_TO_REJECT;
fill_record(thd, table->field, values, TRUE, FALSE);
@ -698,6 +700,20 @@ bool st_select_lex_unit::exec()
add_rows+= (ulonglong) (thd->limit_found_rows - (ulonglong)
((table->file->stats.records - records_at_start)));
}
if (thd->killed == ABORT_QUERY)
{
/*
Stop execution of the remaining queries in the UNIONS, and produce
the current result.
*/
push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
ER_QUERY_EXCEEDED_ROWS_EXAMINED_LIMIT,
ER(ER_QUERY_EXCEEDED_ROWS_EXAMINED_LIMIT),
thd->accessed_rows_and_keys,
thd->lex->limit_rows_examined->val_uint());
thd->killed= NOT_KILLED;
break;
}
}
}
@ -706,6 +722,11 @@ bool st_select_lex_unit::exec()
{
List<Item_func_match> empty_list;
empty_list.empty();
/*
Disable LIMIT ROWS EXAMINED in order to produce the possibly incomplete
result of the UNION without interruption due to exceeding the limit.
*/
thd->lex->limit_rows_examined_cnt= ULONGLONG_MAX;
if (!thd->is_fatal_error) // Check if EOM
{
@ -726,7 +747,7 @@ bool st_select_lex_unit::exec()
fake_select_lex->options, result)))
{
fake_select_lex->table_list.empty();
DBUG_RETURN(TRUE);
goto err;
}
fake_select_lex->join->no_const_tables= TRUE;
@ -798,6 +819,8 @@ bool st_select_lex_unit::exec()
}
}
thd->lex->current_select= lex_select_save;
err:
thd->lex->set_limit_rows_examined();
DBUG_RETURN(saved_error);
}