CREATE INDEX

  • reference
    +

    The CREATE INDEX statement allows you to create a secondary index. Secondary indexes contain a filtered or a full set of keys in a given keyspace. Secondary indexes are optional but increase query efficiency on a keyspace.

    Purpose

    In Couchbase Server 7.0 and later, CREATE INDEX allows you to make multiple concurrent index creation requests. The command starts a task to create the index definition in the background. If there is an index creation task already running, the Index Service queues the incoming index creation request. CREATE INDEX returns as soon as the index creation phase is complete.

    By default, when the index creation phase is complete, the Index Service triggers the index build phase. If you lose connectivity, the index build operation continues in the background. You can defer the index build phase using the defer_build clause. In deferred build mode, CREATE INDEX creates the index definition, but does not trigger the index build phase. You can then build the index using the BUILD INDEX command.

    You can create multiple identical secondary indexes on a keyspace and place them on separate nodes for better index availability. In Couchbase Server Enterprise Edition, the recommended way to do this is using the num_replica option. In Couchbase Server Community Edition, you need to create multiple identical indexes and place them using the nodes option. Refer to WITH Clause below for more details.

    Prerequisites

    RBAC Privileges

    User executing the CREATE INDEX statement must have the Query Manage Index privilege granted on the keyspace. For more details about user roles, see Authorization.

    Syntax

    create-index ::= 'CREATE' 'INDEX' index-name ( 'IF' 'NOT' 'EXISTS' )? 'ON' keyspace-ref
                     '(' index-key lead-key-attribs? ( ( ',' index-key key-attribs? )+ )? ')'
                     index-partition? where-clause? index-using? index-with?
    Syntax diagram: refer to source code listing
    index-name

    [Required] A unique name that identifies the index.

    Valid GSI index names can contain any of the following characters: A-Z a-z 0-9 # _, and must start with a letter, [A-Z a-z]. The minimum length of an index name is 1 character and there is no maximum length set for an index name. When querying, if the index name contains a # or _ character, you must enclose the index name within backticks.

    keyspace-ref

    [Required] Specifies the keyspace where the index is created. Refer to Keyspace Reference below.

    index-key

    [Required] Specifies an index key. Refer to Index Key below.

    lead-key-attribs

    [Optional] Specifies attributes for the leading index key. Refer to Index Key Attributes below.

    key-attribs

    [Optional] Specifies attributes for a non-leading index key. Refer to Index Key Attributes below.

    index-partition

    [Optional] Specifies index partitions. Refer to PARTITION BY HASH Clause below.

    where-clause

    [Optional] Specifies filters for a partial index. Refer to WHERE Clause below.

    index-using

    [Optional] Specifies the index type. Refer to USING Clause below.

    index-with

    [Optional] Specifies options for the index. Refer to WITH Clause below.

    IF NOT EXISTS Clause

    The optional IF NOT EXISTS clause enables the statement to complete successfully when the specified index already exists. If an index with the same name already exists within the specified keyspace, then:

    • If this clause is not present, an error is generated.

    • If this clause is present, the statement does nothing and completes without error.

    Keyspace Reference

    keyspace-ref ::= keyspace-path | keyspace-partial
    Syntax diagram: refer to source code listing

    Specifies the keyspace for which the index needs to be created. The keyspace reference may be a keyspace path or a keyspace partial.

    If there is a hyphen (-) inside any part of the keyspace reference, you must wrap that part of the keyspace reference in backticks (` `). Refer to the examples below.

    Keyspace Path

    keyspace-path ::= ( namespace ':' )? bucket ( '.' scope '.' collection )?
    Syntax diagram: refer to source code listing

    If the keyspace is a named collection, or the default collection in the default scope within a bucket, the keyspace reference may be a keyspace path. In this case, the query context should not be set.

    namespace

    (Optional) An identifier that refers to the namespace of the keyspace. Currently, only the default namespace is available. If the namespace name is omitted, the default namespace in the current session is used.

    bucket

    (Required) An identifier that refers to the bucket name of the keyspace.

    scope

    (Optional) An identifier that refers to the scope name of the keyspace. If omitted, the bucket’s default scope is used.

    collection

    (Optional) An identifier that refers to the collection name of the keyspace. If omitted, the default collection in the bucket’s default scope is used.

    For example, default:`travel-sample` indicates the default collection in the default scope in the travel-sample bucket in the default namespace.

    Similarly, default:`travel-sample`.inventory.airline indicates the airline collection in the inventory scope in the travel-sample bucket in the default namespace.

    Keyspace Partial

    keyspace-partial ::= collection
    Syntax diagram: refer to source code listing

    Alternatively, if the keyspace is a named collection, the keyspace reference may be just the collection name with no path. In this case, you must set the query context to indicate the required namespace, bucket, and scope.

    collection

    (Required) An identifier that refers to the collection name of the keyspace.

    For example, airline indicates the airline collection, assuming the query context is set.

    Index Key

    index-key ::= expr | array-expr
    Syntax diagram: refer to source code listing

    Refers to an attribute name or a scalar function or an ARRAY expression on the attribute. This constitutes an index-key for the index.

    expr

    A SQL++ expression over any fields in the document. This cannot use constant expressions, aggregate functions, or sub-queries.

    array-expr

    An array expression. Array indexing enables you to create global indexes on array elements and optimize the execution of queries involving array elements. For details, refer to Array Indexing.

    Index Key Attributes

    lead-key-attribs ::= index-order include-missing? | include-missing index-order?
    Syntax diagram: refer to source code listing
    key-attribs ::= index-order
    Syntax diagram: refer to source code listing

    Specifies attributes for the index key.

    index-order

    [Optional] All index keys may include an index order clause. Refer to Index Order below.

    include-missing

    [Optional] The leading index key may also include INCLUDE MISSING clause. Refer to INCLUDE MISSING Clause below.

    Index Order

    index-order ::= 'ASC' | 'DESC'
    Syntax diagram: refer to source code listing

    Specifies the sort order of the index key.

    ASC

    The index key is sorted in ascending order.

    DESC

    The index key is sorted in descending order.

    This clause is optional; if omitted, the default is ASC.

    INCLUDE MISSING Clause

    include-missing ::= 'INCLUDE' 'MISSING'
    Syntax diagram: refer to source code listing

    The optional INCLUDE MISSING clause ensures that documents which do not include the index key field are indexed regardless. If this clause is not present, then documents without the index key field are not indexed.

    The INCLUDE MISSING clause can only be applied to the leading index key. The INCLUDE MISSING clause may be included before or after the ASC or DESC keyword.

    PARTITION BY HASH Clause

    Used to partition the index. Index partitioning helps increase the query performance by dividing and spreading a large index of documents across multiple nodes, horizontally scaling out an index as needed. For details, refer to Index Partitioning.

    WHERE Clause

    where-clause ::= 'WHERE' cond
    Syntax diagram: refer to source code listing
    cond

    Specifies WHERE clause predicates to qualify the subset of documents to include in the index.

    USING Clause

    index-using ::= 'USING' 'GSI'
    Syntax diagram: refer to source code listing

    In Couchbase Server 6.5 and later, the index type for a secondary index must be Global Secondary Index (GSI). The USING GSI keywords are optional and may be omitted.

    WITH Clause

    index-with ::= 'WITH' expr
    Syntax diagram: refer to source code listing

    Use the WITH clause to specify additional options.

    expr

    An object with the following properties:

    nodes

    [Optional] An array of strings, each of which represents a node name.

    In Couchbase Server Community Edition, a single global secondary index can be placed on a single node that runs the indexing service. The nodes property allows you to specify the node that the index is placed on. If nodes is not specified, one of the nodes running the indexing service is randomly picked for the index.

    In Couchbase Server Enterprise Edition, you can specify multiple nodes to distribute replicas of an index across nodes running the indexing service: for example, WITH {"nodes": ["node1:8091", "node2:8091", "node3:8091"]}. For details and examples, refer to Index Replication.

    If specifying both nodes and num_replica, the number of nodes in the array must be one greater than the specified number of replicas otherwise the index creation will fail.

    If nodes is not specified, then the system chooses nodes on which to place the new index and any replicas, in order to achieve the best resource utilization across nodes running the indexing service. This is done by taking into account the current resource usage statistics of index nodes.

    A node name passed to the nodes property must include the cluster administration port, by default 8091. For example WITH {"nodes": ["192.0.2.0:8091"]} instead of WITH {"nodes": ["192.0.2.0"]}.
    defer_build

    [Optional] Boolean.

    true

    When set to true, the CREATE INDEX operation queues the task for building the index but immediately pauses the building of the index of type GSI. Index building requires an expensive scan operation. Deferring building of the index with multiple indexes can optimize the expensive scan operation. Admins can defer building multiple indexes and, using the BUILD INDEX statement, multiple indexes to be built efficiently with one efficient scan of bucket data.

    false

    When set to false, the CREATE INDEX operation queues the task for building the index and immediately kicks off the building of the index of type GSI.

    num_replica

    This property is only available in Couchbase Server Enterprise Edition.

    [Optional] Integer that specifies the number of replicas of the index to create.

    The indexer will automatically distribute these replicas amongst index nodes in the cluster for load-balancing and high availability purposes. The indexer will attempt to distribute the replicas based on the server groups in use in the cluster where possible.

    If the value of this property is not less than the number of index nodes in the cluster, then the index creation will fail.

    Usage

    It is not recommended to create (or drop) secondary indexes when any node with a secondary index role is down, as this may result in duplicate index names.

    Monitoring Indexes

    Index metadata provides a state field. This state field and other index metadata can be queried using system:indexes. The index state may be scheduled for creation, deferred, building, pending, online, offline, or abridged. You can also monitor the index state using the Couchbase Web Console.

    If you kick off multiple index creation operations concurrently, you may sometimes see transient errors similar to the following. If this error occurs, the Index Service tries to run the failed operation again in the background until it succeeds, up to a maximum of 1000 retries.

    [
      {
        "code": 5000,
        "msg": "GSI CreateIndex() - cause: Encountered transient error.  Index creation will be retried in background.  Error: Index ... will retry building in the background for reason: Build Already In Progress. Keyspace ...",
        "query": "..."
      }
    ]

    If the Index Service still cannot create the index after the maximum number of retries, the index state is marked as offline. You must drop the failed index using the DROP INDEX command.

    Using the meta().id Function

    You can create indexes on metadata information. For details, refer to Indexing Meta Info.

    Using Indexes for Aggregates

    If you have an index on a simple expression, such as geo.alt, you can use that index to satisfy a query on an aggregate of that expression, such as MIN(geo.alt) or MAX(geo.alt). For details and examples, refer to Operator Pushdowns.

    Index Replicas

    In the Indexes screen in the Couchbase Web Console, index replicas are marked with their replica ID.

    The Indexes screen showing an index and index replica with replica ID

    If you select view by server node from the drop-down menu, you can see the server node where each index and index replica is placed.

    You can also query the system:indexes catalog to find the ID of an index replica and see which node it is placed on.

    By default, index replicas are used to serve index scans. The system automatically load-balances an index scan across the index and all its replicas. Adding index replicas enables you to scale scan throughput, in addition to providing high availability.

    Examples

    To try the examples in this section, you must set the query context as described in each example.

    Example 1. Create an index in the default scope and collection

    For this example, unset the query context. For more information, see Query Context.

    Create a secondary index that contains airports with an alt value greater than 1000 on the node 127.0.0.1.

    CREATE INDEX idx_default_over1000
      ON `travel-sample`(geo.alt)
      WHERE geo.alt > 1000
      USING GSI
      WITH {"nodes": ["127.0.0.1:8091"]};
    Example 2. Create an index in a named scope and collection

    For this example, the path to the required keyspace is specified by the query, so you do not need to set the query context.

    Create a secondary index that contains airports with an alt value greater than 1000 on the node 127.0.0.1.

    CREATE INDEX idx_airport_over1000
      ON `travel-sample`.inventory.airport(geo.alt)
      WHERE geo.alt > 1000
      USING GSI
      WITH {"nodes": ["127.0.0.1:8091"]};
    Example 3. Create a deferred index

    For this example, set the query context to the inventory scope in the travel sample dataset. For more information, see Query Context.

    Create a secondary index with the defer_build option.

    CREATE INDEX idx_landmark_country
      ON landmark(country)
      USING GSI
      WITH {"defer_build":true};

    Query system:indexes for the status of the index.

    SELECT * FROM system:indexes WHERE name="idx_landmark_country";
    Results
    [
      {
        "indexes": {
          "bucket_id": "travel-sample",
          "datastore_id": "http://127.0.0.1:8091",
          "id": "d079aec40eb0c6cc",
          "index_key": [
            "`country`"
          ],
          "keyspace_id": "landmark",
          "name": "idx_landmark_country",
          "namespace_id": "default",
          "scope_id": "inventory",
          "state": "deferred", (1)
          "using": "gsi"
        }
      }
    ]
    1 Note that the index is in the deferred state.
    Example 4. Build a deferred index

    For this example, set the query context to the inventory scope in the travel sample dataset. For more information, see Query Context.

    Kick off a deferred build using the index name.

    BUILD INDEX ON landmark(idx_landmark_country) USING GSI;

    Query system:indexes for the status of the index.

    SELECT * FROM system:indexes WHERE name="idx_landmark_country";
    Results
    [
      {
        "indexes": {
          "bucket_id": "travel-sample",
          "datastore_id": "http://127.0.0.1:8091",
          "id": "d079aec40eb0c6cc",
          "index_key": [
            "`country`"
          ],
          "keyspace_id": "landmark",
          "name": "idx_landmark_country",
          "namespace_id": "default",
          "scope_id": "inventory",
          "state": "online", (1)
          "using": "gsi"
        }
      }
    ]
    1 Note that the index has now been created.
    Example 5. Create index with missing leading key

    For this example, set the query context to the inventory scope in the travel sample dataset. For more information, see Query Context.

    The following statement will not index airports where the district field is missing.

    CREATE INDEX idx_airport_missing
    ON airport(district, name);

    The following statement will index all airports, even if the district field is not included in the document.

    CREATE INDEX idx_airport_include
    ON airport(district INCLUDE MISSING, name);

    For more examples of indexes where the leading key may be missing, see Index Selection.