[SOLVED] MySQL LOAD DATA INFILE with ON DUPLICATE KEY UPDATE

Issue

For loading huge amounts of data into MySQL, LOAD DATA INFILE is by far the fastest option. Unfortunately, while this can be used in a way INSERT IGNORE or REPLACE works, ON DUPLICATE KEY UPDATE is not currently supported.

However, ON DUPLICATE KEY UPDATE has advantages over REPLACE. The latter does a delete and an insert when a duplicate exists. This brings overhead for key management. Also, autoincrement ids will not stay the same on a replace.

How can ON DUPLICATE KEY UPDATE be emulated when using LOAD DATA INFILE?

Solution

These steps can be used to emulate this functionality:

  1. Create a new temporary table.

    CREATE TEMPORARY TABLE temporary_table LIKE target_table;
    
  2. Optionally, drop all indices from the temporary table to speed things up.

    SHOW INDEX FROM temporary_table;
    DROP INDEX `PRIMARY` ON temporary_table;
    DROP INDEX `some_other_index` ON temporary_table;
    
  3. Load the CSV into the temporary table

    LOAD DATA INFILE 'your_file.csv'
    INTO TABLE temporary_table
    FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
    (field1, field2);
    
  4. Copy the data using ON DUPLICATE KEY UPDATE

    SHOW COLUMNS FROM target_table;
    INSERT INTO target_table
    SELECT * FROM temporary_table
    ON DUPLICATE KEY UPDATE field1 = VALUES(field1), field2 = VALUES(field2);
    
  5. Remove the temporary table

    DROP TEMPORARY TABLE temporary_table;
    

Using SHOW INDEX FROM and SHOW COLUMNS FROM this process can be automated for any given table.

Answered By – Jan

Answer Checked By – Marie Seifert (BugsFixing Admin)

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