ZooKeeper schema

/metadata

Table schema.

date column -> legacy MergeTree partition expression.
sampling expression -> SAMPLE BY
index granularity -> index_granularity
mode -> type of MergeTree table
sign column -> sign - CollapsingMergeTree / VersionedCollapsingMergeTree
primary key -> ORDER BY key if PRIMARY KEY not defined.
sorting key -> ORDER BY key if PRIMARY KEY defined.
data format version -> 1
partition key -> PARTITION BY
granularity bytes -> index_granularity_bytes

types of MergeTree tables:
Ordinary            = 0
Collapsing          = 1
Summing             = 2
Aggregating         = 3
Replacing           = 5
Graphite            = 6
VersionedCollapsing = 7

/mutations

Log of latest mutations

/columns

List of columns for latest (reference) table version. Replicas would try to reach this state.

/log

Log of latest actions with table. Used mostly for debug purposes. Related settings:

┌─name────────────────────────┬─value─┬─changed─┬─description────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┬─type───┐
 max_replicated_logs_to_keep  1000         0  How many records may be in log, if there is inactive replica. Inactive replica becomes lost when when this number exceed.                                                   UInt64 
 min_replicated_logs_to_keep  10           0  Keep about this number of last records in ZooKeeper log, even if they are obsolete. It doesn't affect work of tables: used only to diagnose ZooKeeper log before cleaning. │ UInt64 │
└─────────────────────────────┴───────┴─────────┴────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴────────┘

/replicas

List of table replicas.

/replicas/replica_name/

/replicas/replica_name/mutation_pointer

Pointer to the latest mutation executed by replica

/replicas/replica_name/log_pointer

Pointer to the latest task from replication_queue executed by replica

/replicas/replica_name/max_processed_insert_time

/replica/replica_name/metadata

Table schema of specific replica

/replica/replica_name/columns

Columns list of specific replica.

/quorum

Used for quorum inserts.