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Version: Nightly

REGION_INFO

The REGION_INFO table provides runtime and manifest metadata for Regions. Use it to inspect a Region's role and state, writable status, sequence numbers, manifest version, Region options, SST format, and the Datanode that reports the Region.

USE INFORMATION_SCHEMA;
DESC REGION_INFO;

The output is as follows:

+------------------------+---------+-----+------+---------+---------------+
| Column                 | Type    | Key | Null | Default | Semantic Type |
+------------------------+---------+-----+------+---------+---------------+
| region_id              | UInt64  |     | NO   |         | FIELD         |
| table_id               | UInt32  |     | NO   |         | FIELD         |
| region_number          | UInt32  |     | NO   |         | FIELD         |
| region_group           | UInt8   |     | NO   |         | FIELD         |
| region_sequence        | UInt32  |     | NO   |         | FIELD         |
| state                  | String  |     | NO   |         | FIELD         |
| role                   | String  |     | NO   |         | FIELD         |
| writable               | Boolean |     | NO   |         | FIELD         |
| committed_sequence     | UInt64  |     | NO   |         | FIELD         |
| flushed_sequence       | UInt64  |     | YES  |         | FIELD         |
| manifest_version       | UInt64  |     | NO   |         | FIELD         |
| compaction_time_window | String  |     | YES  |         | FIELD         |
| region_options         | String  |     | NO   |         | FIELD         |
| sst_format             | String  |     | NO   |         | FIELD         |
| node_id                | UInt64  |     | YES  |         | FIELD         |
+------------------------+---------+-----+------+---------+---------------+

Fields in the REGION_INFO table are described as follows:

  • region_id: The ID of the Region.
  • table_id: The ID of the table that the Region belongs to.
  • region_number: The Region number inside the table.
  • region_group: The Region group encoded in the Region ID.
  • region_sequence: The Region sequence inside the group.
  • state: The full runtime role and state of the Region. Possible values include Follower, Leader(Writable), Leader(Staging), Leader(EnteringStaging), Leader(Altering), Leader(Dropping), Leader(Truncating), Leader(Editing), and Leader(Downgrading).
  • role: The coarse Region role, Leader or Follower.
  • writable: Whether the Region accepts writes.
  • committed_sequence: The committed sequence of the Region.
  • flushed_sequence: The latest sequence persisted into SSTs. The value is NULL if no sequence has been flushed.
  • manifest_version: The manifest version of the Region.
  • compaction_time_window: The human-readable compaction time window of the Region.
  • region_options: The Region options encoded as JSON.
  • sst_format: The SST format used by the Region, such as primary_key or flat.
  • node_id: The ID of the Datanode that reports the row. The value can be NULL when the row is not reported by a Datanode.

Query a table's Region runtime and manifest information as follows:

SELECT
  i.region_id,
  i.state,
  i.role,
  i.writable,
  i.committed_sequence,
  i.flushed_sequence,
  i.manifest_version,
  i.compaction_time_window,
  i.region_options,
  i.sst_format,
  i.node_id
FROM REGION_INFO i
WHERE i.region_id IN (
  SELECT region_id FROM REGION_PEERS WHERE table_name = 'system_metrics'
)
ORDER BY i.region_id;

Query the maximum manifest version difference between leaders and followers as follows:

SELECT
  MAX(
    CAST(l.manifest_version AS INT64) - CAST(f.manifest_version AS INT64)
  ) AS max_manifest_version_diff
FROM REGION_INFO l
JOIN REGION_INFO f ON l.region_id = f.region_id
WHERE l.role = 'Leader' AND f.role = 'Follower';

To find the Region and Datanode pair with the largest manifest version difference, use the following query:

SELECT
  l.region_id,
  l.node_id AS leader_node_id,
  f.node_id AS follower_node_id,
  l.manifest_version AS leader_manifest_version,
  f.manifest_version AS follower_manifest_version,
  CAST(l.manifest_version AS INT64) - CAST(f.manifest_version AS INT64)
    AS manifest_version_diff
FROM REGION_INFO l
JOIN REGION_INFO f ON l.region_id = f.region_id
WHERE l.role = 'Leader' AND f.role = 'Follower'
ORDER BY manifest_version_diff DESC
LIMIT 1;