Error : MySQL server has gone away

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- July 21, 2004 at 11:20 pm #8506
  
  dbischoff
  Member
  
  Does anyone know what causes this error in a batch execute?
  
  I'm trying to execute a SQL batch to insert records into ane empty table, which are from a copy of the same database on another mySQL server.
  
  none of the records get inserted before it fails.
  
  The other batches I have used to update this database have worked, but this table is larger, about 8500 records totalling 9Mb of data. I have also used a SQL batch identical to this to load this data into the first database with no problem, so there appears to be a difference in the behavior of the two mySQL systems.
- July 22, 2004 at 11:39 am #16107
  
  Ritesh
  Member
  
  Are the SQL in form of BULK INSERT STATEMENTS?
- July 26, 2004 at 8:03 am #16108
  
  Shadow
  Member
  
  You should try increasing max_allowed_packet variable in the config file.
- August 1, 2004 at 10:50 pm #16109
  
  dbischoff
  Member
  
  Thanks for the help, one or both of these suggestions will likely solve it.
  
  I think I used BULK INSERTS. I'll try turning that off. I'll also look at the mySQL max_allowed_packet setting. I believe there is none entered into my my.cnf file, so it is probably at default.
- August 3, 2004 at 3:11 pm #16110
  
  Shadow
  Member
  
  Some MySql versions have an exteremely low limit on max_allowed_packet by default!
- August 3, 2004 at 4:00 pm #16111
  
  peterlaursen
  Participant
  
  On my system max_allowed_packet was 1 M as installed. I don't know how to interpret that value, but hasd a porblem with restoring backups. I raised the value to 10 M and subsequently 100 M and can't feel any performance degradance or other “backends” ….
- August 3, 2004 at 8:10 pm #16112
  
  Shadow
  Member
  
  max_allowed_packet variable limits the maximum size of SQL statements. Let's say you have a table in which you store pictures in a BLOB column. If you have a max_allowed_packet parameter set to (or left at) 1M then you will not be able to store pictures in this table that exceed 1MB in size, even if the column type allow for more data to be held, as the SQL statement is limited in length. Increasing this parameter has no immediate performance effect because 1. it does not speed up anything, merely allows more data to be sent to MySql in an SQL statement; 2. the buffer is not initialized to this value, buffer of this length is used only when needed.
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