# oushu_locks

The `oushu_locks` view provides access to information about the distributed locks held by all main node within OushuDB.The `oushu_locks` view is similar to [pg_locks](./pg_locks.md). `pg_locks` can only privide information about lock held by the node which execute `pg_locks` query.



Table 1. `pg_catalog.oushu_locks`

| column          | type     | references      | description                                                  |
| :-------------- | :------- | :-------------- | :----------------------------------------------------------- |
| `locktype`      | text     |                 | Type of the lockable object: `relation`, `extend`, `page`, `tuple`, `transactionid`, `object`, `userlock`, `resource queue`, or `advisory` |
| `database`      | oid      | pg_database.oid | OID of the database in which the object exists, zero if the object is a shared object, or NULL if the object is a transaction ID |
| `relation`      | oid      | pg_class_internal.oid    | OID of the relation, or NULL if the object is not a relation or part of a relation |
| `page`          | integer  |                 | Page number within the relation, or NULL if the object is not a tuple or relation page |
| `tuple`         | smallint |                 | Tuple number within the page, or NULL if the object is not a tuple |
| `virtualxid`    | text      |                 | Virtual ID of a transaction, or NULL if the object is not a virtual transaction ID |
| `transactionid` | xid      |                 | ID of a transaction, or NULL if the object is not a transaction ID |
| `classid`       | oid      | pg_class_internal.oid    | OID of the system catalog containing the object, or NULL if the object is not a general database object |
| `objid`         | oid      | any OID column  | OID of the object within its system catalog, or NULL if the object is not a general database object |
| `objsubid`      | smallint |                 | For a table column, this is the column number (the `classid` and `objid` refer to the table itself). For all other object types, this column is zero. NULL if the object is not a general database object |
| `virtualtransaction`   | text      |                 | Virtual ID of the transaction that is holding or awaiting this lock  |
| `ip`           | text  |                 | The IP address of main node |
| `pid`           | integer  |                 | Process ID of the server process holding or awaiting this lock. NULL if the lock is held by a prepared transaction |
| `mode`          | text     |                 | Name of the lock mode held or desired by this process        |
| `granted`       | boolean  |                 | True if lock is held, false if lock is awaited.              |
| `fastpath`       | boolean  |                 | 	True if lock was taken via fastpath, false if lock is taken via main lock table. |
| `mppsessionid`  | integer  |                 | The id of the client session associated with this lock.      |
| `mppiswriter`   | boolean  |                 | Specifies whether the lock is held by a writer process.      |
| `gp_segment_id` | integer  |                 | The OushuDB segment id (`dbid`) where the lock is held.         |