MYSQL insertion limit, mysql limit_PHP tutorial
Jul 12, 2016 am 08:51 AM
MYSQL insertion limit, mysql limit
1. If many rows are inserted from the same client at the same time, use an INSERT statement containing multiple VALUEs to insert several rows at the same time. This is faster (in some cases several times faster) than using a single-line INSERT statement. If you are adding data to a non-empty table, you can adjust the bulk_insert_buffer_size variable to make data insertion faster. See Section 5.3.3, “Server System Variables”.
2. If you insert many rows from different clients, you can speed up the process by using the INSERT DELAYED statement. See Section 13.2.4, “INSERT Syntax”.
3. Using MyISAM, if there are no deleted rows in the table, rows can be inserted while the SELECT statement is running.
4. When loading a table from a text file, use LOAD DATA INFILE. This is typically 20 times faster than using many INSERT statements. See Section 13.2.5, “LOAD DATA INFILE Syntax”.
5. When the table has many indexes, it may be necessary to do more work to make LOAD DATA INFILE faster. Use the following process:
1). Selectively create a table with CREATE TABLE.
2). Execute the FLUSH TABLES statement or the command mysqladmin flush-tables.
3). Use myisamchk --keys-used=0 -rq /path/to/db/tbl_name. This will unuse all indexes from the table.
4). Use LOAD DATA INFILE to insert data into the table. Because no index is updated, it is very fast.
5). If you only want to read the table later, use myisampack to compress it. See Section 15.1.3.3, “Compression Table Properties”.
6). Use myisamchk -r -q /path/to/db/tbl_name to re-create the index. This will create the index tree in memory before writing to disk, and it is faster because large disk searches are avoided. The resulting index tree is also perfectly balanced.
7). Execute the FLUSH TABLES statement or mysqladmin flush-tables command.
6. Locking the table can speed up INSERT operations executed with multiple statements:
* 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 will improve performance because the index cache is only flushed to disk once after all INSERT statements are completed. Generally, the number of INSERT statements is the number of index cache refreshes. If you can insert all rows with one statement, no locking is needed.
For transactional tables, BEGIN and COMMIT should be used instead of LOCK TABLES to speed up insertions.
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