Why is MySQL InnoDB insert so slow

Question

I am using large random numbers as keys  coming in from another system    Inserts and updates on fairly-small  as in a few million rows  tables are taking much longer than I think is reasonable   I have distilled a very simple test to illustrate   In the test table I ve tried to make it as simple as possible  my real code does not have such a simple layout and has relations and additional indices and such   However  a simpler setup shows equivalent performance   Here are the results   creating the MyISAM table took 0 000 seconds creating 1024000 rows of test data took 1 243 seconds inserting the test data took 6 335 seconds selecting 1023742 rows of test data took 1 435 seconds fetching 1023742 batches of test data took 0 037 seconds dropping the table took 0 089 seconds creating the InnoDB table took 0 276 seconds creating 1024000 rows of test data took 1 165 seconds inserting the test data took 3433 268 seconds selecting 1023748 rows of test data took 4 220 seconds fetching 1023748 batches of test data took 0 037 seconds dropping the table took 0 288 seconds   Inserting 1M rows into MyISAM takes 6 seconds  into InnoDB takes 3433 seconds   What am I doing wrong   What is misconfigured    MySQL is a normal Ubuntu installation with defaults   Here s the test code   import sys  time  random import MySQLdb as db    usage  python script db username db password database name  db   db connect host  127 0 0 1  port 3306 user sys argv 1  passwd sys argv 2  db sys argv 3   cursor    def test engine        start   time time     fine for this purpose     db execute     CREATE TEMPORARY TABLE Testing123   k INTEGER PRIMARY KEY NOT NULL  v VARCHAR 255  NOT NULL   ENGINE  s     engine      duration   time time  -start     print  creating the  s table took  0 3f seconds   engine duration       start   time time         1 million rows in 100 chunks of 10K     data      str random getrandbits 48   if a amp 1 else int random getrandbits 31    for a in xrange 10 1024 2   for b in xrange 100       duration   time time  -start     print  creating  d rows of test data took  0 3f seconds   sum len rows  2 for rows in data  duration       sql    REPLACE INTO Testing123  k v  VALUES  s       s  s     10 1024    -1      start   time time       for rows in data          db execute sql rows      duration   time time  -start     print  inserting the test data took  0 3f seconds  duration        execute the query     start   time time       query   db execute  SELECT k v FROM Testing123        duration   time time  -start     print  selecting  d rows of test data took  0 3f seconds   query duration         get the rows in chunks of 10K     rows   0     start   time time       while query          batch   min query 10 1024          query -  batch         rows    len db fetchmany batch       duration   time time  -start     print  fetching  d batches of test data took  0 3f seconds   rows duration         drop the table     start   time time       db execute  DROP TABLE Testing123        duration   time time  -start     print  dropping the table took  0 3f seconds  duration   test  MyISAM   test  InnoDB

User · Answer

What s your innodb buffer-pool size  Make sure you ve set it to 75  of your RAM  Usually inserts are better when in primary key order for InnoDB  But with a big pool-size  you should see good speeds

User · Answer

This is an old topic but frequently searched  So long as you are aware of risks  as stated by  philip Koshy above  of losing committed transactions in the last one second or so  before massive updates  you may set these global parameters  innodb flush log at trx commit 0 sync binlog 0   then turn then back on  if so desired  after update is complete   innodb flush log at trx commit 1 sync binlog 1   for full ACID compliance   There is a huge difference in write update performance when both of these are turned off and on   In my experience  other stuff discussed above makes some difference but only marginal     One other thing that impacts update insert greatly is full text index   In one case  a table with two text fields having full text index  inserting 2mil rows took 6 hours and the same took only 10 min after full text index was removed   More indexes  more time  So search indexes other than unique and primary key may be removed prior to massive inserts updates

User · Answer

The default value for InnoDB is actually pretty bad  InnoDB is very RAM dependent  you might find better result if you tweak the settings  Here s a guide that I used InnoDB optimization basic

User · Answer

things that speed up the inserts    i had removed all keys from a table  before large insert into empty table then found i had a problem that the index did not fit in memory   also found i had sync binlog 0  should be 1  even if binlog is not used   also found i did not set innodb buffer pool instances

User · Answer

InnoDB doesn t cope well with  random  primary keys  Try a sequential key or auto-increment  and I believe you ll see better performance  Your  real  key field could still be indexed  but for a bulk insert you might be better off dropping and recreating that index in one hit after the insert in complete  Would be interested to see your benchmarks for that   Some related questions   Slow INSERT into InnoDB table with random PRIMARY KEY column s value Why do MySQL InnoDB inserts   updates on large tables get very slow when there are a few indexes  InnoDB inserts very slow and slowing down

User · Answer

Solution   Create new UNIQUE key that is identical to your current PRIMARY key Add new column id is unsigned integer  auto increment Create primary key on new id column   Bam  immediate 10x  insert improvement

User · Answer

I get very different results on my system  but this is not using the defaults   You are likely bottlenecked on innodb-log-file-size  which is 5M by default   At innodb-log-file-size 100M I get results like this  all numbers are in seconds                                 MyISAM     InnoDB create table                  0 001      0 276 create 1024000 rows           2 441      2 228 insert test data             13 717     21 577 select 1023751 rows           2 958      2 394 fetch 1023751 batches         0 043      0 038 drop table                    0 132      0 305   Increasing the innodb-log-file-size will speed this up by a few seconds   Dropping the durability guarantees by setting innodb-flush-log-at-trx-commit 2 or 0 will improve the insert numbers somewhat as well

User · Answer

InnoDB has transaction support  you re not using explicit transactions so innoDB has to do a commit after each statement   performs a log flush to disk for every insert     Execute this command before your loop   START TRANSACTION   and this after you loop  COMMIT

User · Answer

I ve needed to do testing of an insert-heavy application in both MyISAM and InnoDB simultaneously  There was a single setting that resolved the speed issues I was having  Try setting the following   innodb flush log at trx commit   2   Make sure you understand the risks by reading about the setting here   Also see https   dba stackexchange com questions 12611 is-it-safe-to-use-innodb-flush-log-at-trx-commit-2 12612 and https   dba stackexchange com a 29974 9405

[mysql] Why is MySQL InnoDB insert so slow?

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