These performance tips supplement the general guidelines for fast inserts in Section
220.127.116.11, "Speed of
MyISAM table, you can use concurrent inserts to
add rows at the same time that
statements are running, if there are no deleted rows in middle of the data file. See Section
8.10.3, "Concurrent Inserts".
With some extra work, it is possible to make
LOAD DATA INFILE run even faster for a
MyISAM table when the table has many indexes. Use the following procedure:
Use myisamchk --keys-used=0 -rq
to remove all use of indexes for the table.
Insert data into the table with
LOAD DATA INFILE. This does not update any indexes and
therefore is very fast.
If you intend only to read from the table in the future, use myisampack to compress it. See Section 18.104.22.168, "Compressed Table Characteristics".
Re-create the indexes with myisamchk -rq
creates the index tree in memory before writing it to disk, which is much faster that
updating the index during
DATA INFILE because it avoids lots of disk seeks. The resulting index tree is
also perfectly balanced.
LOAD DATA INFILE performs the preceding optimization automatically if
MyISAM table into which you insert data is empty. The main
difference between automatic optimization and using the procedure explicitly is that you can let myisamchk
allocate much more temporary memory for the index creation than you might want the server to
allocate for index re-creation when it executes the
LOAD DATA INFILE statement.
tbl_nameDISABLE KEYS;ALTER TABLE
To speed up
INSERT operations that are performed with multiple statements for
nontransactional tables, lock your tables:
LOCK TABLES a WRITE;INSERT INTO a VALUES (1,23),(2,34),(4,33);INSERT INTO a VALUES (8,26),(6,29);...UNLOCK TABLES;
This benefits performance because the index buffer is flushed to disk only once, after all
statements have completed. Normally, there would be as many index buffer flushes as there are
INSERT statements. Explicit locking statements are not needed if
you can insert all rows with a single
Locking also lowers the total time for multiple-connection tests, although the maximum wait time for individual connections might go up because they wait for locks. Suppose that five clients attempt to perform inserts simultaneously as follows:
Connection 1 does 1000 inserts
Connections 2, 3, and 4 do 1 insert
Connection 5 does 1000 inserts
If you do not use locking, connections 2, 3, and 4 finish before 1 and 5. If you use locking, connections 2, 3, and 4 probably do not finish before 1 or 5, but the total time should be about 40% faster.
DELETE operations are very fast in MySQL, but you can obtain
better overall performance by adding locks around everything that does more than about five
successive inserts or updates. If you do very many successive inserts, you could do a
TABLES followed by an
UNLOCK TABLES once in a while (each 1,000 rows or so) to permit
other threads to access table. This would still result in a nice performance gain.
To increase performance for
MyISAM tables, for both
LOAD DATA INFILE and
INSERT, enlarge the key cache by increasing the
key_buffer_size system variable. See Section
8.11.2, "Tuning Server Parameters".