Getting System Information
N1QL has a system catalog that stores metadata about a database. The system catalog is a namespace called system.
There is a keyspace for each type of artifact. The keyspace names are plural in order to avoid conflicting with N1QL keywords.
Logical Hierarchy
N1QL has the following artifacts:
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Datastores
Datastores are similar to sites. A datastore is a database deployment, for example, a server cluster, cloud service, or mobile installation. It is analogous to a relation database instance.
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Namespaces
Namespaces are similar to pools. A namespace is a unit of authorization, resource allocation, and tenancy. It is analogous to a relational database or schema.
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Keyspaces
Keyspaces map to buckets in Couchbase Server. A keyspace is a set of documents that may vary in structure. It is a unit of authorization and resource allocation. It is analogous to a relational database table.
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Indexes
An index on a keyspace. It is analogous to a relational database index. Types of indexes include b-tree (ForestDB or MOI) and view indexes.
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Dual
The dual keyspace has been added for evaluating constant expressions. It contains a single entry with no attributes.
Querying Datastores
You can query datastores using the SELECT statement as follows:
SELECT * FROM system:datastores
The query returns the following attributes:
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id: string (id for the datastore) -
url: string (URL for the datastore instance)
Querying Namespaces
You can query namespaces using the SELECT statement as follows:
SELECT * FROM system:namespaces
The query returns the following attributes:
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id: string (id for the namespace) -
name: string (name for the namespace) -
store_id: string (id for the datastore to which the namespace belongs)
Querying Keyspaces
You can query keyspaces using the SELECT statement as follows:
SELECT * FROM system:keyspaces
The query returns the following attributes:
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id: string (id for the keyspace) -
name: string (name for the keyspace) -
namespace_id: string (id for the namespace to which the keyspace belongs) -
store_id: string (id for the datastore to which the keyspace belongs)
Querying Indexes
You can query indexes using the SELECT statement as follows:
SELECT * FROM system:indexes
The query returns the following attributes:
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id: string (id for the index) -
name: string (name for the index) -
index_key: array of strings (list of index keys) -
index_type: string (type of index, for example, view index) -
keyspace_id: string (id for the keyspace to which the index belongs) -
namespace_id: string (id for the namespace to which the index belongs) -
store_id: string (id for the datastore to which the index belongs)