ob_default_lob_inrow_threshold

Description

The ob_default_lob_inrow_threshold variable specifies the default row-based storage threshold for LOB fields when a table is created.

Privilege requirements

• Query a variable

  • Global level

    sys tenants and user tenants can execute the SHOW VARIABLES statement or view the information_schema.GLOBAL_VARIABLES view (MySQL mode) to query the value of a global system variable.

  • Session level

    sys tenants and user tenants can execute the SHOW VARIABLES statement or view the information_schema.SESSION_VARIABLES view (MySQL mode) to query the value of a session system variable.

• Modify a variable

  • Global level

    • sys tenants can directly modify the value of a global system variable.

    • MySQL user tenants must have the SUPER or ALTER SYSTEM privilege to modify the value of a global system variable.

  • Session level

    sys tenants and user tenants can directly modify the value of a session system variable in their own tenant.

Attributes

Considerations

ob_default_lob_inrow_threshold is a global-level system variable that actually affects the table-level attribute lob_inrow_threshold of newly created tables (existing tables are not affected). Modifying the system variable ob_default_lob_inrow_threshold will impact the in-row and out-of-row storage threshold for LOB columns in newly created tables, while modifying the table-level attribute lob_inrow_threshold will affect the in-row and out-of-row storage for that specific table. If lob_inrow_threshold is not specified when creating a table, the value of the system variable ob_default_lob_inrow_threshold will be used as the threshold for in-row and out-of-row storage of LOB columns in that table.

Examples

The following examples show how to set the value of ob_default_lob_inrow_threshold without specifying LOB_INROW_THRESHOLD:

1. Set the value of ob_default_lob_inrow_threshold to 40960 bytes.

   • Session level

     obclient> SET ob_default_lob_inrow_threshold = 40960;
     

   • Global level

     obclient> SET GLOBAL ob_default_lob_inrow_threshold = 40960;
     

2. Create a table named t without specifying LOB_INROW_THRESHOLD.

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

   In this case, the value of the ob_default_lob_inrow_threshold variable is used as the INROW threshold for the t table, which is 40960 bytes.