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ALTER TAG

ALTER TAG alters the structure of a tag with the given name in a graph space. You can add or drop properties, and change the data type of an existing property. You can also set a TTL (Time-To-Live) on a property, or change its TTL duration.

Notes

  • Running the ALTER TAG statement requires some privileges for the graph space. Otherwise, NebulaGraph throws an error.
  • Before you alter properties for a tag, make sure that the properties are not indexed. If the properties contain any indexes, the conflict error [ERROR (-1005)]: Conflict! will occur when you ALTER TAG. For more information on dropping an index, see DROP INDEX.
  • The property name must be unique in a tag. If you add a property with the same name as an existing property or a dropped property, the operation fails.

Syntax

ALTER TAG <tag_name>
    <alter_definition> [[, alter_definition] ...]
    [ttl_definition [, ttl_definition] ... ]
    [COMMENT '<comment>'];

alter_definition:
| ADD    (prop_name data_type [NULL | NOT NULL] [DEFAULT <default_value>] [COMMENT '<comment>'])
| DROP   (prop_name)
| CHANGE (prop_name data_type [NULL | NOT NULL] [DEFAULT <default_value>] [COMMENT '<comment>'])

ttl_definition:
    TTL_DURATION = ttl_duration, TTL_COL = prop_name
  • tag_name: Specifies the tag name that you want to alter. You can alter only one tag in one statement. Before you alter a tag, make sure that the tag exists in the current working graph space. If the tag does not exist, an error will occur when you alter it.
  • Multiple ADD, DROP, and CHANGE clauses are permitted in a single ALTER TAG statement, separated by commas.
  • When a property value is set to NOT NULL using ADD or CHANGE, a default value must be specified for the property, that is, the value of DEFAULT must be specified.

  • When using CHANGE to modify the data type of a property:

    • Only the length of a FIXED_STRING or an INT can be increased. The length of a STRING or an INT cannot be decreased.
    • Only the data type conversions from FIXED_STRING to STRING and from FLOAT to DOUBLE are allowed.

Examples

nebula> CREATE TAG IF NOT EXISTS t1 (p1 string, p2 int);
nebula> ALTER TAG t1 ADD (p3 int32, fixed_string(10));
nebula> ALTER TAG t1 TTL_DURATION = 2, TTL_COL = "p2";
nebula> ALTER TAG t1 COMMENT = 'test1';
nebula> ALTER TAG t1 ADD (p5 double NOT NULL DEFAULT 0.4 COMMENT 'p5') COMMENT='test2';
// Change the data type of p3 in the TAG t1 from INT32 to INT64, and that of p4 from FIXED_STRING(10) to STRING.
nebula> ALTER TAG t1 CHANGE (p3 int64, p4 string);
[ERROR(-1005)]: Unsupported!

Implementation of the operation

Trying to use a newly altered tag may fail because the alteration of the tag is implemented asynchronously. To make sure the follow-up operations work as expected, Wait for two heartbeat cycles, i.e., 20 seconds.

To change the heartbeat interval, modify the heartbeat_interval_secs parameter in the configuration files for all services.

Last update: October 24, 2023