Order by and pagination - mysql

Question

I have a thousand of records in my database mysql and I use pagination to retrieve just 10 results.
When i add a order by in my query it slow down but when i omit it the query run very fast.
I know that the problem come from that the query load whole results, sort them and after that it get the 10 records.
I don't use index because the column use for order is a PK and i think if i'm not wrong in mysql a index is created automatically on every primary key
Why the index on my PK which is the column I'm ordering.
not used ?
Is there any alternative solution to perform sorting without load all the data ?
How to add new inserted data at the first row of tables and not at the end of the table ?
My sql query
select distinct ...... order by appeloffre0_.ID_APPEL_OFFRE desc limit 10
and my indexes
mysql> show index from appel_offre;
+-------------+------------+--------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------------+------------+--------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| appel_offre | 0 | PRIMARY | 1 | ID_APPEL_OFFRE | A | 13691 | NULL | NULL | | BTREE | | |
| appel_offre | 1 | appel_offre_ibfk_1 | 1 | ID_APPEL_OFFRE_MERE | A | 2 | NULL | NULL | YES | BTREE | | |
| appel_offre | 1 | appel_offre_ibfk_2 | 1 | ID_ACHETEUR | A | 2 | NULL | NULL | | BTREE | | |
| appel_offre | 1 | appel_offre_ibfk_3 | 1 | USER_SAISIE | A | 2 | NULL | NULL | YES | BTREE | | |
| appel_offre | 1 | appel_offre_ibfk_4 | 1 | USER_VALIDATION | A | 4 | NULL | NULL | YES | BTREE | | |
| appel_offre | 1 | ao_fk_3 | 1 | TYPE_MARCHE | A | 2 | NULL | NULL | YES | BTREE | | |
| appel_offre | 1 | ao_fk_5 | 1 | USER_CONTROLE | A | 2 | NULL | NULL | YES | BTREE | | |
+-------------+------------+--------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
7 rows in set (0.03 sec)
no index was chosen in explain cmd:
+----+-------------+---------------+--------+-------------------------------------+--------------------+---------+----------------
| id | select_type | table | type | possible_keys | key | key_len | ref
+----+-------------+---------------+--------+-------------------------------------+--------------------+---------+----------------
| 1 | SIMPLE | appeloffre0_ | ALL | NULL | NULL | NULL | NULL
UPDATE SOLUTION
the problem was from distinct when i delete it the query finnaly use the index.

Answer 1

Because you already use an index on "USER_VALIDATION", MySQL won't use the ID index instead.
Try rebuilding the USER_VALIDATION index to include the ID too:
CREATE UNIQUE INDEX appel_offre_ibfk_4 ON appel_offre (USER_VALIDATION, ID);
Update
Log all Hibernate queries, extract the slow query and use EXPLAIN in a db console to understand what execution plan MySQL selects for this query. It may be possible for the db to use a FULL TABLE SCAN even when you have an index, because the index is too large to fit into memory. Try giving it a HINT as explained in this post.
According to MySQL ORDER BY optimization documentation you should:
To increase ORDER BY speed, check whether you can get MySQL to use indexes rather than an extra sorting phase. If this is not possible, you can try the following strategies:
• Increase the sort_buffer_size variable value.
• Increase the read_rnd_buffer_size variable value.
• Use less RAM per row by declaring columns only as large as they need
to be to hold the values stored in them. For example, CHAR(16) is
better than CHAR(200) if values never exceed 16 characters.
• Change the tmpdir system variable to point to a dedicated file
system with large amounts of free space. The variable value can list
several paths that are used in round-robin fashion; you can use this
feature to spread the load across several directories. Paths should be
separated by colon characters (“:”) on Unix and semicolon characters
(“;”) on Windows, NetWare, and OS/2. The paths should name directories
in file systems located on different physical disks, not different
partitions on the same disk.
Also make sure DISTINCT doesn't overrule your index. Try removing it and see if it helps.

Answer 2

Add an index to the column by which you are ordering.
You can't add rows to the beginning of the table, just like you can't add rows to the end of the table. Database tables are multisets. Multisets are by definition unordered collections. The notion of a first element or a last element makes no sense for multisets.