Collection Methods

Collection Methods

Drop

drops a collection collection.drop(options)

Drops a collection and all its indexes and data. In order to drop a system collection, an options object with attribute isSystem set to true must be specified.

Dropping a collection in a cluster, which is prototype for sharing in other collections is prohibited. In order to be able to drop such a collection, all dependent collections must be dropped first.

Examples

arangosh> col = db.example;
arangosh> col.drop();
arangosh> col;

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[ArangoCollection 75587, "example" (type document, status loaded)]
[ArangoCollection 75587, "example" (type document, status deleted)]

arangosh> col = db._example;
arangosh> col.drop({ isSystem: true });
arangosh> col;

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[ArangoCollection 75594, "_example" (type document, status loaded)]
[ArangoCollection 75594, "_example" (type document, status deleted)]

Truncate

truncates a collection collection.truncate()

Truncates a collection, removing all documents but keeping all its indexes.

Examples

Truncates a collection:

arangosh> col = db.example;
arangosh> col.save({ "Hello" : "World" });
arangosh> col.count();
arangosh> col.truncate();
arangosh> col.count();

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[ArangoCollection 75748, "example" (type document, status loaded)]
{ 
  "_id" : "example/75753", 
  "_key" : "75753", 
  "_rev" : "_dAzP06a---" 
}
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Compact

Introduced in: v3.4.5

Compacts the data of a collection collection.compact()

Compacts the data of a collection in order to reclaim disk space. For the MMFiles storage engine, the operation will reset the collection’s last compaction timestamp, so it will become a candidate for compaction. For the RocksDB storage engine, the operation will compact the document and index data by rewriting the underlying .sst files and only keeping the relevant entries.

Under normal circumstances running a compact operation is not necessary, as the collection data will eventually get compacted anyway. However, in some situations, e.g. after running lots of update/replace or remove operations, the disk data for a collection may contain a lot of outdated data for which the space shall be reclaimed. In this case the compaction operation can be used.

Properties

gets or sets the properties of a collectioncollection.properties()

Returns an object containing all collection properties.

waitForSync: If true creating a document will only return after the data was synced to disk.
journalSize : The size of the journal in bytes. This option is meaningful for the MMFiles storage engine only.
isVolatile: If true then the collection data will be kept in memory only and ArangoDB will not write or sync the data to disk. This option is meaningful for the MMFiles storage engine only.
keyOptions (optional) additional options for key generation. This is a JSON array containing the following attributes (note: some of the attributes are optional):
- type: the type of the key generator used for the collection.
- allowUserKeys: if set to true, then it is allowed to supply own key values in the _key attribute of a document. If set to false, then the key generator will solely be responsible for generating keys and supplying own key values in the _key attribute of documents is considered an error.
- increment: increment value for autoincrement key generator. Not used for other key generator types.
- offset: initial offset value for autoincrement key generator. Not used for other key generator types.
schema (optional, default is null): Object that specifies the collection level document schema for documents. The attribute keys rule, level and message must follow the rules documented in Document Schema Validation

In a cluster setup, the result will also contain the following attributes:

numberOfShards: the number of shards of the collection.
shardKeys: contains the names of document attributes that are used to determine the target shard for documents.
replicationFactor: determines how many copies of each shard are kept on different DB-Servers. Has to be in the range of 1-10 or the string "satellite" for a SatelliteCollection (Enterprise Edition only). (cluster only)
writeConcern: determines how many copies of each shard are required to be in sync on the different DB-Servers. If there are less then these many copies in the cluster a shard will refuse to write. Writes to shards with enough up-to-date copies will succeed at the same time however. The value of writeConcern can not be larger than replicationFactor. (cluster only)
shardingStrategy: the sharding strategy selected for the collection. This attribute will only be populated in cluster mode and is not populated in single-server mode. (cluster only)

collection.properties(properties)

Changes the collection properties. properties must be an object with one or more of the following attribute(s):

waitForSync: If true creating a document will only return after the data was synced to disk.
journalSize: The size of the journal in bytes. This option is meaningful for the MMFiles storage engine only.
replicationFactor: Change the number of shard copies kept on different DB-Servers. Valid values are integer numbers in the range of 1-10 or the string "satellite" for a SatelliteCollection (Enterprise Edition only). (cluster only)
writeConcern: change how many copies of each shard are required to be in sync on the different DB-Servers. If there are less then these many copies in the cluster a shard will refuse to write. Writes to shards with enough up-to-date copies will succeed at the same time however. The value of writeConcern can not be larger than replicationFactor. (cluster only)

Note: some other collection properties, such as type, isVolatile, keyOptions, numberOfShards or shardingStrategy cannot be changed once the collection is created.

Examples

Read all properties

arangosh> db.example.properties();
{ 
  "isSystem" : false, 
  "waitForSync" : false, 
  "keyOptions" : { 
    "allowUserKeys" : true, 
    "type" : "traditional", 
    "lastValue" : 0 
  }, 
  "writeConcern" : 1, 
  "cacheEnabled" : false, 
  "schema" : null 
}

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arangosh> db.example.properties();

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Change a property

arangosh> db.example.properties({ waitForSync : true });
{ 
  "isSystem" : false, 
  "waitForSync" : true, 
  "keyOptions" : { 
    "allowUserKeys" : true, 
    "type" : "traditional", 
    "lastValue" : 0 
  }, 
  "writeConcern" : 1, 
  "cacheEnabled" : false, 
  "schema" : null 
}

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arangosh> db.example.properties({ waitForSync : true });

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Figures

returns the figures of a collection collection.figures(details)

Returns an object containing statistics about the collection.

Setting details to true will return extended storage engine-specific details to the figures (introduced in v3.7.3). The details are intended for debugging ArangoDB itself and their format is subject to change. By default, details is set to false, so no details are returned and the behavior is identical to previous versions of ArangoDB.

indexes.count: The total number of indexes defined for the collection, including the pre-defined indexes (e.g. primary index).
indexes.size: The total memory allocated for indexes in bytes.
documentsSize
cacheInUse
cacheSize
cacheUsage

Examples

arangosh> db.demo.figures()

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{ 
  "indexes" : { 
    "count" : 1, 
    "size" : 1781 
  }, 
  "documentsSize" : 16830, 
  "cacheInUse" : false, 
  "cacheSize" : 0, 
  "cacheUsage" : 0 
}

arangosh> db.demo.figures(true)

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{ 
  "indexes" : { 
    "count" : 1, 
    "size" : 1781 
  }, 
  "documentsSize" : 16830, 
  "cacheInUse" : false, 
  "cacheSize" : 0, 
  "cacheUsage" : 0, 
  "engine" : { 
    "documents" : 1, 
    "indexes" : [ 
      { 
        "type" : "primary", 
        "id" : 0, 
        "count" : 1 
      } 
    ] 
  } 
}

GetResponsibleShard

returns the responsible shard for the given document. collection.getResponsibleShard(document)

Returns a string with the responsible shard’s ID. Note that the returned shard ID is the ID of responsible shard for the document’s shard key values, and it will be returned even if no such document exists.

The getResponsibleShard() method can only be used on Coordinators in clusters.

Shards

returns the available shards for the collection. collection.shards(details)

If details is not set, or set to false, returns an array with the names of the available shards of the collection.

If details is set to true, returns an object with the shard names as object attribute keys, and the responsible servers as an array mapped to each shard attribute key.

The leader shards are always first in the arrays of responsible servers.

The shards() method can only be used on Coordinators in clusters.

Load

loads a collection collection.load()

Loads a collection into memory.

Cluster collections are loaded at all times.

Examples

arangosh> col = db.example;
arangosh> col.load();
arangosh> col;

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[ArangoCollection 75675, "example" (type document, status loaded)]
[ArangoCollection 75675, "example" (type document, status loaded)]

Revision

returns the revision id of a collection collection.revision()

Returns the revision id of the collection

The revision id is updated when the document data is modified, either by inserting, deleting, updating or replacing documents in it.

The revision id of a collection can be used by clients to check whether data in a collection has changed or if it is still unmodified since a previous fetch of the revision id.

The revision id returned is a string value. Clients should treat this value as an opaque string, and only use it for equality/non-equality comparisons.

Path

returns the physical path of the collection collection.path()

The path operation returns a string with the physical storage path for the collection data.

The path() method will return nothing meaningful in a cluster. In a single-server ArangoDB, this method will only return meaningful data for the MMFiles storage engine.

Checksum

calculates a checksum for the data in a collection collection.checksum(withRevisions, withData)

The checksum operation calculates an aggregate hash value for all document keys contained in collection collection.

If the optional argument withRevisions is set to true, then the revision ids of the documents are also included in the hash calculation.

If the optional argument withData is set to true, then all user-defined document attributes are also checksummed. Including the document data in checksumming will make the calculation slower, but is more accurate.

The checksum calculation algorithm changed in ArangoDB 3.0, so checksums from 3.0 and earlier versions for the same data will differ.

The checksum() method can not be used in clusters.

Unload

unloads a collection collection.unload()

Starts unloading a collection from memory. Note that unloading is deferred until all query have finished.

Cluster collections cannot be unloaded.

Examples

arangosh> col = db.example;
arangosh> col.unload();
arangosh> col;

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[ArangoCollection 65565, "example" (type document, status loaded)]
[ArangoCollection 65565, "example" (type document, status unloaded)]

Rename

renames a collection collection.rename(new-name)

Renames a collection using the new-name. The new-name must not already be used for a different collection. new-name must also be a valid collection name. For more information on valid collection names please refer to the naming conventions.

If renaming fails for any reason, an error is thrown. If renaming the collection succeeds, then the collection is also renamed in all graph definitions inside the _graphs collection in the current database.

The rename() method can not be used in clusters.

Examples

arangosh> c = db.example;
arangosh> c.rename("better-example");
arangosh> c;

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[ArangoCollection 75739, "example" (type document, status loaded)]
[ArangoCollection 75739, "better-example" (type document, status loaded)]