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InnoDB takes over an hour to import 600MB file, MyISAM in a few minutes

Posted by: admin November 1, 2017 Leave a comment


I’m currently working on creating an environment to test performance of an app; I’m testing with MySQL and InnoDB to find out which can serve us best. Within this environment, we’ll automatically prepare the database (load existing dumps) and instrument our test tools.

I’m preparing to test the same data dump with MySQL and InnoDB, but I’m already failing to bring the initial import to an usable speed for the InnoDB part. The initial dump took longer, but that didn’t concerned me yet:

$ for i in testdb_myisam testdb_innodb; do time mysqldump --extended-insert $i > $i.sql; done

real    0m38.152s
user    0m8.381s
sys     0m2.612s

real    1m16.665s
user    0m6.600s
sys     0m2.552s

However, the import times were quite different:

$ for i in  testdb_myisam testdb_innodb; do time mysql $i < $i.sql; done

real    2m52.821s
user    0m10.505s
sys     0m1.252s

real    87m36.586s
user    0m10.637s
sys     0m1.208s

After research I came over Changing tables from MyISAM to InnoDB make the system slow and then used set global innodb_flush_log_at_trx_commit=2:

$ time mysql testdb_innodb < testdb_innodb.sql

real    64m8.348s
user    0m10.533s
sys     0m1.152s

IMHO still shockingly slow. I’ve also disabled log_bin for these tests and here’s a list of all mysql variables.

Do I’ve to accept this long InnoDB times or can they be improved? I’ve full control over this MySQL server as it’s purely for this test environment.

I can apply special configurations only for initial import and change them back for applications tests so they better match production environments.


Given the feedback, I’ve disabled autocommit and the various checks:

$ time ( echo "SET autocommit=0; SET unique_checks=0; SET foreign_key_checks=0;" \
; cat testdb_innodb.sql ; echo "COMMIT;" ) | mysql testdb_innodb;date

real    47m59.019s
user    0m10.665s
sys     0m2.896s

The speed improved, but not that much. Is my test flawed?

Update 2:

I was able to gain access to a different machine were imports only took about 8 minutes. I compared the configurations and applied the following settings to my MySQL installation:

innodb_additional_mem_pool_size = 20971520
innodb_buffer_pool_size = 536870912
innodb_log_buffer_size = 8388608
join_buffer_size = 67104768
max_allowed_packet = 5241856
max_binlog_size = 1073741824
max_heap_table_size = 41943040
query_cache_limit = 10485760
query_cache_size = 157286400
read_buffer_size = 20967424
sort_buffer_size = 67108856
table_cache = 256
thread_cache_size = 128
thread_stack = 327680
tmp_table_size = 41943040

With these settings I’m now down to about 25 minutes. Still far away from the few minutes MyISAM takes, but it’s getting more usable for me.


Did you try the Bulk Data Loading Tips from the InnoDB Performance Tuning Tips (especially the first one):

  • When importing data into InnoDB, make sure that MySQL does not have
    autocommit mode enabled because that
    requires a log flush to disk for every
    insert. To disable autocommit during
    your import operation, surround it
    with SET autocommit and COMMIT

    SET autocommit=0;
    ... SQL import statements ...

    If you use the mysqldump option --opt, you get dump files that are
    fast to import into an InnoDB table,
    even without wrapping them with the
    SET autocommit and COMMIT

  • If you have UNIQUE constraints on secondary keys, you can speed up table
    imports by temporarily turning off the
    uniqueness checks during the import

    SET unique_checks=0;
    ... SQL import statements ...
    SET unique_checks=1;

    For big tables, this saves a lot of disk I/O because InnoDB can use
    its insert buffer to write secondary
    index records in a batch. Be certain
    that the data contains no duplicate

  • If you have FOREIGN KEY constraints in your tables, you can
    speed up table imports by turning the
    foreign key checks off for the
    duration of the import session:

    SET foreign_key_checks=0;
    ... SQL import statements ...
    SET foreign_key_checks=1;

    For big tables, this can save a lot of disk I/O.

IMO, the whole chapter is worth the read.


Have you tried starting a transaction at the outset and committing it at the end? From the question you linked: “Modify the Insert Data step to start a transaction at the start and to commit it at the end. You will get an improvement, I guarantee it.”

Remember that InnoDB is transactional, MyISAM is not. Transactional engines treat every statement as an individual transaction if you don’t explicitly control the transaction. This can be costly.


I had issues doing a lot of bulk importing and recommend the accepted answer. I found you can also speed things up significantly by:

  1. Dropping all indexes (other than primary key), loading the data then re-adding indexes
  2. Checking your innodb_log_file_size * innodb_log_files_in_group is sufficient to avoid writing to disk in sub-second frequency

Regarding #2 the defaults of 5M * 2 will not be enough on a modern system. For details see innodb_log_file_size and innodb_log_files_in_group


I found the hard drive to be the bottleneck – old-fashioned disks are hopeless, SSD is okay-ish but still far from perfect. Importing to tmpfs and copying out the data is way faster, details: https://dba.stackexchange.com/a/89367/56667