Set bulk_insert_sql_str_length_limit Parameter

Customer Managed Applies to customer-managed instances of Alation

Alation extracts metadata from data sources and inserts the extracted metadata information into Postgres in batches. The bulk_insert_sql_str_length_limit parameter sets the batch size for bulk metadata synchronization. The default value is 500 MB set in bytes: alation.metadata_syncing.bulk_insert_sql_str_length_limit = 500000000.

Users may have to adjust the value of this parameter using alation_conf if they observe performance issues during metadata extraction (MDE), such as extreme slowness that leads to MDE failure. The postgres.log in this case will contain Out of Memory errors and the information on MDE failure during the execution of the Insert query. Analysis by Alation engineers shows that in such cases the Insert query may be terminated by the operating system due to memory pressure.

Alation does not currently provide a specific recommendation for the bulk_insert_sql_str_length_limit value because it largely depends on the instance size and resources. You may need to experimentally find the value that works for your Alation instance.

To configure bulk_insert_sql_str_length_limit :

  1. SSH to your Alation host.

  2. Enter the Alation shell:

    sudo /etc/init.d/alation shell
  3. To view the current value of the bulk_insert_sql_str_length_limit, run:

    alation_conf alation.metadata_syncing.bulk_insert_sql_str_length_limit
  1. To set a new value, run the following command substituting <value in bytes> by the actual value:

    alation_conf alation.metadata_syncing.bulk_insert_sql_str_length_limit -s <value in bytes>

You can start with reducing the default value of the parameter by half and re-running the MDE from Alation to check if it runs successfully.