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system.keeper_storage

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Description

The table only exists for ClickHouse Keeper deployments that use the clickhouse server (and not clickhouse keeper) process. It contains one row per node of the data tree stored on the local Keeper node, including the /keeper system nodes.

Unlike system.zookeeper, this table does not send requests to a Keeper cluster. It reads the committed state of the local Keeper directly from a consistent lock-free view, without affecting request processing. Reading the table does not require a path condition and returns the whole tree, so it is suitable for queries that scan all nodes, such as finding the nodes with the most children or the largest data.

Columns

  • path (String) — Absolute path of the node.
  • data (String) — Data stored in the node.
  • czxid (Int64) — ID of the transaction that created the node.
  • mzxid (Int64) — ID of the transaction that last modified the node.
  • ctime (DateTime64(3)) — Time when the node was created.
  • mtime (DateTime64(3)) — Time when the node was last modified.
  • version (Int32) — Number of modifications of the node data.
  • cversion (Int32) — Number of modifications of the node children.
  • aversion (Int32) — Number of modifications of the node ACL.
  • ephemeral_owner (Int64) — ID of the session that owns the node if it is ephemeral, 0 otherwise.
  • data_length (UInt32) — Size of the node data in bytes.
  • num_children (Int32) — Number of children of the node.
  • pzxid (Int64) — ID of the transaction that last added or removed children of the node.
  • seq_num (Int64) — Counter used to generate names of sequential children of the node.
  • ttl (Int64) — TTL of the node in milliseconds if it is a TTL node, 0 otherwise.
  • acl_id (UInt32) — Internal ID of the node ACL, 0 if the node has no ACL.

Example

SELECT path, num_children, data_length
FROM system.keeper_storage
ORDER BY num_children DESC
LIMIT 3;
┌─path──────────────┬─num_children─┬─data_length─┐
│ /                 │            3 │           0 │
│ /clickhouse/tasks │            2 │           0 │
│ /keeper           │            1 │           0 │
└───────────────────┴──────────────┴─────────────┘
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