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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.

Prerequisites

  • Running the ALTER TAG statement requires some privileges for the graph space. Otherwise, Nebula Graph 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 (-8)]: Conflict! will occur when you ALTER TAG. For more information on dropping an index, see DROP INDEX.

Syntax

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

alter_definition:
| ADD    (prop_name data_type)
| DROP   (prop_name)
| CHANGE (prop_name data_type)

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.

Examples

nebula> CREATE TAG t1 (p1 string, p2 int);
nebula> ALTER TAG t1 ADD (p3 int, p4 string);
nebula> ALTER TAG t1 TTL_DURATION = 2, TTL_COL = "p2";
nebula> ALTER TAG t1 COMMENT = 'test1';

Implementation of the operation

Trying to use a newly altered tag may fail because the alteration of the tag is implemented asynchronously.

Nebula Graph implements the alteration of the tag in the next heartbeat cycle. To make sure the alteration is successful, take one of the following approaches:

  • Use DESCRIBE TAG to confirm that the tag information is updated. If it is not, wait a few seconds and try again.
  • 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: August 30, 2021
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