These performance tips supplement the general guidelines for
fast inserts in Section 184.108.40.206, “Speed of
MyISAM table, you can use
concurrent inserts to add rows at the same time that
SELECT 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
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
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 220.127.116.11, “Compressed Table Characteristics”.
Re-create the indexes with myisamchk -rq
This creates the index tree in memory before writing it
to disk, which is much faster that updating the index
DATA INFILE because it avoids lots of disk
seeks. The resulting index tree is also perfectly
INFILE performs the preceding optimization
automatically if the
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
DATA INFILE statement.
tbl_nameDISABLE KEYS; ALTER TABLE
To speed up
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
INSERT statements have
completed. Normally, there would be as many index buffer
flushes as there are
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
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
tables, for both
enlarge the key cache by increasing the
variable. See Section 8.11.2, “Tuning Server Parameters”.