ob_default_lob_inrow_threshold

Overview

ob_default_lob_inrow_threshold specifies the default threshold for storing LOB fields within rows during table creation.

Privilege requirements

• Query variables

  • Global level

    Both the sys tenant and all user tenants can use the SHOW VARIABLES statement or the information_schema.GLOBAL_VARIABLES view (in MySQL-compatible mode) to view the values of global system variables.

  • Session level

    The sys tenant and all user tenants can use the SHOW VARIABLES statement or the information_schema.SESSION_VARIABLES view (in MySQL-compatible mode) to view the values of session system variables.

• Modify variables

  • Global effective

    • The sys tenant can directly modify the values of global system variables.

    • MySQL user tenants must have the SUPER or ALTER SYSTEM privilege to modify the values of global system variables.

  • Session expiration

    The sys tenant and all user tenants can directly modify the values of session system variables for their own tenants.

Attributes

Usage instructions

• If LOB_INROW_THRESHOLD is not specified when creating a table, the value of this variable will be written into the table schema.
• Modifying the value of this variable does not affect the INROW threshold for tables that have already been created. It only affects newly created tables that do not specify LOB_INROW_THRESHOLD.

Configuration example

An example where LOB_INROW_THRESHOLD is not specified is as follows:

1. Set the value of ob_default_lob_inrow_threshold to 40,960 bytes.

   • Settings at the session level

     obclient> SET ob_default_lob_inrow_threshold = 40960;
     

   • Settings at the global level

     obclient> SET GLOBAL ob_default_lob_inrow_threshold = 40960;
     

2. Create table t without specifying LOB_INROW_THRESHOLD.

   obclient> CREATE TABLE t(pk int, data text);
   

   In this case, the value of the system variable ob_default_lob_inrow_threshold is used as the threshold. That is, the INROW threshold for table t is 40,960 bytes.