MySQL Reference Manual :: 7.2.14 Speed of INSERT Statements

Connecting: (3)

Sending query to server: (2)

Parsing query: (2)

Inserting record: (1 x size of record)

Inserting indexes: (1 x number of indexes)

Closing: (1)

If you are inserting many rows from the same client at the same time, use INSERT statements with multiple VALUES lists to insert several rows at a time. This is much faster (many times faster in some cases) than using separate single-row INSERT statements. If you are adding data to a non-empty table, you may tune the bulk_insert_buffer_size variable to make it even faster. See Section 5.2.3, “Server System Variables”.

If you are inserting a lot of rows from different clients, you can get higher speed by using the INSERT DELAYED statement. See Section 13.1.4, “INSERT Syntax”.

With MyISAM tables you can insert rows at the same time that SELECT statements are running if there are no deleted rows in the tables.

When loading a table from a text file, use LOAD DATA INFILE. This is usually 20 times faster than using a lot of INSERT statements. See Section 13.1.5, “LOAD DATA INFILE Syntax”.

With some extra work, it is possible to make LOAD DATA INFILE run even faster when the table has many indexes. Use the following procedure:

Note that LOAD DATA INFILE also performs the preceding optimization if you insert into an empty MyISAM table; the main difference 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.

As of MySQL 4.0, you can also use ALTER TABLE tbl_name DISABLE KEYS instead of myisamchk --keys-used=0 -rq /path/to/db/tbl_name and ALTER TABLE tbl_name ENABLE KEYS instead of myisamchk -r -q /path/to/db/tbl_name. This way you can also skip the FLUSH TABLES steps.

You can speed up INSERT operations that are done with multiple statements by locking 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;

A performance benefit occurs 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 different INSERT statements. Explicit locking statements are not needed if you can insert all rows with a single statement.

For transactional tables, you should use BEGIN/COMMIT instead of LOCK TABLES to get a speedup.

Locking also lowers the total time of multiple-connection tests, although the maximum wait time for individual connections might go up because they wait for locks. For example:

Connection 1 does 1000 inserts
Connections 2, 3, and 4 do 1 insert
Connection 5 does 1000 inserts

If you don't 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.

INSERT, UPDATE, and 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 inserts or updates in a row. If you do very many inserts in a row, you could do a LOCK TABLES followed by an UNLOCK TABLES once in a while (about each 1,000 rows) to allow other threads access to the table. This would still result in a nice performance gain.

INSERT is still much slower for loading data than LOAD DATA INFILE, even when using the strategies just outlined.

To get some more speed for MyISAM tables, for both LOAD DATA INFILE and INSERT, enlarge the key cache by increasing the key_buffer_size system variable. See Section 7.5.2, “Tuning Server Parameters”.