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BUG#10037: A proper fix: Add 0.01 to cost of 'range' scans, don't add 0.01 to cost of the 'index' scan.

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sergefp@mysql.com
2005-04-26 01:56:10 +04:00
parent 83c289665f
commit a27e830385
1 changed files with 11 additions and 6 deletions
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17
sql/opt_range.cc
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@ -2257,8 +2257,7 @@ inline double get_index_only_read_time(const PARAM* param, ha_rows records,
param->table->file->ref_length) + 1); param->table->file->ref_length) + 1);
read_time=((double) (records+keys_per_block-1)/ read_time=((double) (records+keys_per_block-1)/
(double) keys_per_block); (double) keys_per_block);
/* Add 0.01 to avoid cost races between 'range' and 'index' */ return read_time;
return read_time + 0.01;
} }
@ -3150,10 +3149,16 @@ static TRP_RANGE *get_key_scans_params(PARAM *param, SEL_TREE *tree,
(param->table->file->index_flags(keynr, param->max_key_part,1) & (param->table->file->index_flags(keynr, param->max_key_part,1) &
HA_KEYREAD_ONLY) && HA_KEYREAD_ONLY) &&
!(pk_is_clustered && keynr == param->table->s->primary_key)) !(pk_is_clustered && keynr == param->table->s->primary_key))
/* We can resolve this by only reading through this key. */ {
/*
We can resolve this by only reading through this key.
0.01 is added to avoid races between range and 'index' scan.
*/
found_read_time= get_index_only_read_time(param,found_records,keynr) + found_read_time= get_index_only_read_time(param,found_records,keynr) +
cpu_cost; cpu_cost + 0.01;
}
else else
{
/* /*
cost(read_through_index) = cost(disk_io) + cost(row_in_range_checks) cost(read_through_index) = cost(disk_io) + cost(row_in_range_checks)
The row_in_range check is in QUICK_RANGE_SELECT::cmp_next function. The row_in_range check is in QUICK_RANGE_SELECT::cmp_next function.
@ -3161,8 +3166,8 @@ static TRP_RANGE *get_key_scans_params(PARAM *param, SEL_TREE *tree,
found_read_time= param->table->file->read_time(keynr, found_read_time= param->table->file->read_time(keynr,
param->range_count, param->range_count,
found_records) + found_records) +
cpu_cost; cpu_cost + 0.01;
}
DBUG_PRINT("info",("key %s: found_read_time: %g (cur. read_time: %g)", DBUG_PRINT("info",("key %s: found_read_time: %g (cur. read_time: %g)",
param->table->key_info[keynr].name, found_read_time, param->table->key_info[keynr].name, found_read_time,
read_time)); read_time));