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 TAGstatement 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 (-8)]: Conflict!will occur when youALTER TAG. For more information on dropping an index, see DROP INDEX.
Syntax¶
```ngql
ALTER TAG
alter_definition:
| ADD (prop_name data_type [NULL | NOT NULL] [DEFAULT
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, andCHANGEclauses are permitted in a singleALTER TAGstatement, separated by commas.
Examples¶
ngql
nebula> CREATE TAG IF NOT EXISTS 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';
nebula> ALTER TAG t1 ADD (p5 double NOT NULL DEFAULT 0.4 COMMENT 'p5') COMMENT='test2';
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.