LOAD DATA INFILE

Syntax

LOAD DATA [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'file_name'
    [REPLACE | IGNORE]
    INTO TABLE tbl_name
    [CHARACTER SET charset_name]
    [{FIELDS | COLUMNS}
        [TERMINATED BY 'string']
        [[OPTIONALLY] ENCLOSED BY 'char']
        [ESCAPED BY 'char']
    ]
    [LINES
        [STARTING BY 'string']
        [TERMINATED BY 'string']
    ]
    [IGNORE number LINES]
    [(col_name_or_user_var,...)]
    [SET col_name = expr,...]

Description

Reads rows from a text file into the designated table on the database at a very high speed. The file name must be given as a literal string.

Files are written to disk using the SELECT INTO OUTFILE statement. You can then read the files back into a table using the LOAD DATA INFILE statement. The FIELDS and LINES clauses are the same in both statements. These clauses are optional, but if both are specified then the FIELDS clause must precede LINES.

In releases after MariaDB 5.5, LOAD DATA INFILE is unsafe for statement-based replication.

Executing this statement activates INSERT triggers.

REPLACE and IGNORE

In cases where you load data from a file into a table that already contains data and has a Primary Key, you may encounter issues where the statement attempts to insert a row with a Primary Key that already exists. When this happens, the statement fails with Error 1064, protecting the data already on the table. In cases where you want MariaDB to overwrite duplicates, use the REPLACE keyword.

The REPLACE keyword works like the REPLACE statement. Here, the statement attempts to load the data from the file. If the row does not exist, it adds it to the table. If the row contains an existing Primary Key, it replaces the table data. That is, in the event of a conflict, it assumes the file contains the desired row.

This operation can cause a degradation in load speed by a factor of 20 or more if the part that has already been loaded is larger than the capacity of the InnoDB Buffer Pool. This happens because it causes a lot of turnaround in the Buffer Pool.

Use the IGNORE keyword when you want to skip any rows that contain a conflicting Primary Key. Here, the statement attempts to load the data from the file. If the row does not exist, it adds it to the table. If the row contains an existing Primary Key, it ignores the addition request and moves on to the next. That is, in the event of a conflict, it assumes the table contains the desired row.

LOCAL

When you issue this statement, the Server attempts to read files from the host file system. Using the LOCAL keyword, the statement instead attempts to read files from the client. This allows you to insert files from the client's local file system into the database.

In the event that you don't want the server to permit this operation, (such as for security reasons), you can disable support using local_infile. When this system variable is set to 0, MariaDB rejects LOAD DATA LOCAL INFILE statements, failing with an error message.

Character-sets

When the statement opens the file, it attempts to read the contents using the default character-set, as defined by the character_set_database system variable.

In the cases where the file was written using a character-set other than the default, you can specify the character-set to use with the CHARACTER SET clause in the statement. It ignores character-sets specified by the SET NAMES statement and by the character_set_client system variable. Setting the CHARACTER SET clause to a value of binary indicates "no conversion."

The statement interprets all fields in the file as having the same character-set, regardless of the column data type. To properly interpret file contents, you must ensure that it was written with the correct character-set. If you write a data file with mysqldump -T or with the SELECT INTO OUTFILE statement with the mysql client, be sure to use the --default-character-set option, so that the output is written with the desired character-set.

When using mixed character sets, use the CHARACTER SET clause in both SELECT INTO OUTFILE and LOAD DATA INFILE to ensure that MariaDB correctly interprets the escape sequences.

The character_set_filesystem system variable controls the interpretation of the filename.

It is currently not possible to load data files that use the ucs2 character set.

Priority and Concurrency

In loading data from a file, there's a risk that the statement will attempt insertions concurrent with reads from another client, which can result in the read serving a result-set that contains only part of the update from the LOAD DATA INFILE statement.

Using the LOW_PRIORITY keyword, MariaDB delays insertions until no other clients are reading from the table. Alternatively, you can use the CONCURRENT keyword to perform concurrent insertion.

The LOW_PRIORITY and CONCURRENT keywords are mutually exclusive. They cannot be used in the same statement.

Progress Reporting

Since MariaDB 5.3, the LOAD DATA INFILE statement supports progress reporting. You may find this useful when dealing with long-running operations. Using another client you can issue a SHOW PROCESSLIST query to check the progress of the data load.

Using mysqlimport

MariaDB ships with a separate utility for loading data from files: mysqlimport. It operates by sending LOAD DATA INFILE statements to the server.

Using mysqlimport you can compress the file using the --compress option, to get better performance over slow networks, providing both the client and server support the compressed protocol. Use the --local option to load from the local file system.

Indexing

In cases where the storage engine supports ALTER TABLE... DISABLE KEYS statements, the LOAD DATA INFILE statement automatically disables indexes during the execution.

See Also

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