2.2 KiB
@brief ensures that a unique skiplist index exists
collection.ensureIndex({ type: "skiplist", fields: [ "field1", ..., "fieldn" ], unique: true })
Creates a unique skiplist index on all documents using field1, ... fieldn as attribute paths. At least one attribute path has to be given. The index will be non-sparse by default.
All documents in the collection must differ in terms of the indexed attributes. Creating a new document or updating an existing document will will fail if the attribute uniqueness is violated.
To create a sparse unique index, set the sparse attribute to true:
collection.ensureIndex({ type: "skiplist", fields: [ "field1", ..., "fieldn" ], unique: true, sparse: true })
In a sparse index all documents will be excluded from the index that do not
contain at least one of the specified index attributes or that have a value
of null in any of the specified index attributes. Such documents will
not be indexed, and not be taken into account for uniqueness checks.
In a non-sparse index, these documents will be indexed (for non-present
indexed attributes, a value of null will be used) and will be taken into
account for uniqueness checks.
In case that the index was successfully created, an object with the index details, including the index-identifier, is returned.
@EXAMPLE_ARANGOSH_OUTPUT{ensureUniqueSkiplist} ~db._create("ids"); db.ids.ensureIndex({ type: "skiplist", fields: [ "myId" ], unique: true }); db.ids.save({ "myId": 123 }); db.ids.save({ "myId": 456 }); db.ids.save({ "myId": 789 }); db.ids.save({ "myId": 123 }); // xpError(ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED) ~db._drop("ids"); @END_EXAMPLE_ARANGOSH_OUTPUT
@EXAMPLE_ARANGOSH_OUTPUT{ensureUniqueSkiplistMultiColmun} ~db._create("ids"); db.ids.ensureIndex({ type: "skiplist", fields: [ "name.first", "name.last" ], unique: true }); db.ids.save({ "name" : { "first" : "hans", "last": "hansen" }}); db.ids.save({ "name" : { "first" : "jens", "last": "jensen" }}); db.ids.save({ "name" : { "first" : "hans", "last": "jensen" }}); | db.ids.save({ "name" : { "first" : "hans", "last": "hansen" }}); ~ // xpError(ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED) ~db._drop("ids"); @END_EXAMPLE_ARANGOSH_OUTPUT