On Tue, Dec 07, 2021 at 07:01:45PM +0300, Sergey Petrunia wrote:
> == Issue #1: ordered index scan is not handled in ha_partition ==
I've hit this again when trying to get range optmizer to work. Please find the
patch below. It follows MySQL-8's approach.
>
> Testcase:
>
> create table t10 (a int, b int, key(a desc)) partition by hash(a) partitions
> 4;
> insert into t10 select seq, seq from seq_0_to_999;
>
> MariaDB [test]> select * from t10 order by a limit 3;
> +------+------+
> | a | b |
> +------+------+
> | 3 | 3 |
> | 7 | 7 |
> | 11 | 11 |
> +------+------+
> 3 rows in set (0.002 sec)
>
> Correct output:
>
> MariaDB [test]> select * from t10 use index() order by a limit 3;
> +------+------+
> | a | b |
> +------+------+
> | 0 | 0 |
> | 1 | 1 |
> | 2 | 2 |
> +------+------+
> 3 rows in set (0.011 sec)
diff --git a/sql/key.cc b/sql/key.cc
index f2cebfe6d82..c43d3c36d5d 100644
--- a/sql/key.cc
+++ b/sql/key.cc
@@ -495,6 +495,7 @@ int key_cmp(KEY_PART_INFO *key_part, const uchar *key, uint
key_length)
{
int cmp;
store_length= key_part->store_length;
+ int sort_order = (key_part->key_part_flag & HA_REVERSE_SORT) ? -1 : 1;
if (key_part->null_bit)
{
/* This key part allows null values; NULL is lower than everything */
@@ -503,19 +504,19 @@ int key_cmp(KEY_PART_INFO *key_part, const uchar *key,
uint key_length)
{
/* the range is expecting a null value */
if (!field_is_null)
- return 1; // Found key is > range
+ return sort_order; // Found key is > range
/* null -- exact match, go to next key part */
continue;
}
else if (field_is_null)
- return -1; // NULL is less than any value
+ return -sort_order; // NULL is less than any value
key++; // Skip null byte
store_length--;
}
if ((cmp=key_part->field->key_cmp(key, key_part->length)) < 0)
- return -1;
+ return -sort_order;
if (cmp > 0)
- return 1;
+ return sort_order;
}
return 0; // Keys are equal
}
@@ -574,6 +575,7 @@ int key_rec_cmp(void *key_p, uchar *first_rec, uchar
*second_rec)
do
{
field= key_part->field;
+ int sort_order = (key_part->key_part_flag & HA_REVERSE_SORT) ? -1 : 1;
if (key_part->null_bit)
{
@@ -593,12 +595,12 @@ int key_rec_cmp(void *key_p, uchar *first_rec, uchar
*second_rec)
; /* Fall through, no NULL fields */
else
{
- DBUG_RETURN(+1);
+ DBUG_RETURN(sort_order);
}
}
else if (!sec_is_null)
{
- DBUG_RETURN(-1);
+ DBUG_RETURN(-sort_order);
}
else
goto next_loop; /* Both were NULL */
@@ -612,7 +614,7 @@ int key_rec_cmp(void *key_p, uchar *first_rec, uchar
*second_rec)
*/
if ((result= field->cmp_prefix(field->ptr+first_diff,
field->ptr+sec_diff,
key_part->length)))
- DBUG_RETURN(result);
+ DBUG_RETURN(result * sort_order);
next_loop:
key_part++;
key_part_num++;
BR
Sergei
--
Sergei Petrunia, Software Developer
MariaDB Corporation | Skype: sergefp | Blog: http://petrunia.net
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