CLEAR SPACE¶

CLEAR SPACE deletes the vertices and edges in a graph space, but does not delete the graph space itself and the schema information.

Note

It is recommended to execute SUBMIT JOB COMPACT immediately after executing the CLEAR SPACE operation improve the query performance. Note that the COMPACT operation may affect query performance, and it is recommended to perform this operation during low business hours (e.g., early morning).

Permission requirements¶

Only the God role has the permission to run CLEAR SPACE.

Caution¶

Once cleared, the data CANNOT be recovered. Use CLEAR SPACE with caution.
CLEAR SPACE is not an atomic operation. If an error occurs, re-run CLEAR SPACE to avoid data remaining.
The larger the amount of data in the graph space, the longer it takes to clear it. If the execution fails due to client connection timeout, increase the value of the storage_client_timeout_ms parameter in the Graph Service configuration.
During the execution of CLEAR SPACE, writing data into the graph space is not automatically prohibited. Such write operations can result in incomplete data clearing, and the residual data can be damaged.

Note

The NebulaGraph Community Edition does not support blocking data writing while allowing CLEAR SPACE.

Enterpriseonly

The NebulaGraph Enterprise Edition supports blocking data writing by setting VARIABLE read_only=true before running CLEAR SPACE. After the data are cleared successfully, run SET VARIABLE read_only=false to allow data writing again.

Syntax¶

CLEAR SPACE [IF EXISTS] <space_name>;

Parameter/Option	Description
`IF EXISTS`	Check whether the graph space to be cleared exists. If it exists, continue to clear it. If it does not exist, the execution finishes, and a message indicating that the execution succeeded is displayed. If `IF EXISTS` is not set and the graph space does not exist, the `CLEAR SPACE` statement fails to execute, and an error occurs.
`space_name`	The name of the space to be cleared.

Example:

CLEAR SPACE basketballplayer;

Data reserved¶

CLEAR SPACE does not delete the following data in a graph space:

Tag information.
Edge type information.
The metadata of native indexes and full-text indexes.

The following example shows what CLEAR SPACE deletes and reserves.

# Enter the graph space basketballplayer.
nebula [(none)]> use basketballplayer;
Execution succeeded

# List tags and Edge types.
nebula[basketballplayer]> SHOW TAGS;
+----------+
| Name     |
+----------+
| "player" |
| "team"   |
+----------+
Got 2 rows

nebula[basketballplayer]> SHOW EDGES;
+----------+
| Name     |
+----------+
| "follow" |
| "serve"  |
+----------+
Got 2 rows

# Submit a job to make statistics of the graph space.
nebula[basketballplayer]> SUBMIT JOB STATS;
+------------+
| New Job Id |
+------------+
| 4          |
+------------+
Got 1 rows

# Check the statistics.
nebula[basketballplayer]> SHOW STATS;
+---------+------------+-------+
| Type    | Name       | Count |
+---------+------------+-------+
| "Tag"   | "player"   | 51    |
| "Tag"   | "team"     | 30    |
| "Edge"  | "follow"   | 81    |
| "Edge"  | "serve"    | 152   |
| "Space" | "vertices" | 81    |
| "Space" | "edges"    | 233   |
+---------+------------+-------+
Got 6 rows

# List tag indexes.
nebula[basketballplayer]> SHOW TAG INDEXES;
+------------------+----------+----------+
| Index Name       | By Tag   | Columns  |
+------------------+----------+----------+
| "player_index_0" | "player" | []       |
| "player_index_1" | "player" | ["name"] |
+------------------+----------+----------+
Got 2 rows

# ----------------------- Dividing line for CLEAR SPACE -----------------------
# Run CLEAR SPACE to clear the graph space basketballplayer.
nebula[basketballplayer]> CLEAR SPACE basketballplayer;
Execution succeeded

# Update the statistics.
nebula[basketballplayer]> SUBMIT JOB STATS;
+------------+
| New Job Id |
+------------+
| 5          |
+------------+
Got 1 rows

# Check the statistics. The tags and edge types still exist, but all the vertices and edges are gone.
nebula[basketballplayer]> SHOW STATS;
+---------+------------+-------+
| Type    | Name       | Count |
+---------+------------+-------+
| "Tag"   | "player"   | 0     |
| "Tag"   | "team"     | 0     |
| "Edge"  | "follow"   | 0     |
| "Edge"  | "serve"    | 0     |
| "Space" | "vertices" | 0     |
| "Space" | "edges"    | 0     |
+---------+------------+-------+
Got 6 rows

# Try to list the tag indexes. They still exist.
nebula[basketballplayer]> SHOW TAG INDEXES;
+------------------+----------+----------+
| Index Name       | By Tag   | Columns  |
+------------------+----------+----------+
| "player_index_0" | "player" | []       |
| "player_index_1" | "player" | ["name"] |
+------------------+----------+----------+
Got 2 rows (time spent 523/978 us)

Last update: February 19, 2024