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Database Methods

Document

db._document(object)

The _document method finds a document given an object object containing the _id attribute. The method returns the document if it can be found.

An error is thrown if _rev is specified but the document found has a different revision already. An error is also thrown if no document exists with the given _id.

Please note that if the method is executed on the arangod server (e.g. from inside a Foxx application), an immutable document object will be returned for performance reasons. It is not possible to change attributes of this immutable object. To update or patch the returned document, it needs to be cloned/copied into a regular JavaScript object first. This is not necessary if the _document method is called from out of arangosh or from any other client.

db._document(document-handle)

As before. Instead of object a document-handle can be passed as first argument. No revision can be specified in this case.

Examples

Returns the document:

arangosh> db._document("example/12345");
show execution results

Exists

db._exists(object)

The _exists method determines whether a document exists given an object object containing the _id attribute.

An error is thrown if _rev is specified but the document found has a different revision already.

Instead of returning the found document or an error, this method will only return an object with the attributes _id, _key and _rev, or false if no document with the given _id or _key exists. It can thus be used for easy existence checks.

This method will throw an error if used improperly, e.g. when called with a non-document handle, a non-document, or when a cross-collection request is performed.

db._exists(document-handle)

As before. Instead of object a document-handle can be passed as first argument.

Changes in 3.0 from 2.8:

In the case of a revision mismatch _exists now throws an error instead of simply returning false. This is to make it possible to tell the difference between a revision mismatch and a non-existing document.

Replace

db._replace(selector, data)

Replaces an existing document described by the selector, which must be an object containing the _id attribute. There must be a document with that _id in the current database. This document is then replaced with the data given as second argument. Any attribute _id, _key or _rev in data is ignored.

The method returns a document with the attributes _id, _key, _rev and _oldRev. The attribute _id contains the document handle of the updated document, the attribute _rev contains the document revision of the updated document, the attribute _oldRev contains the revision of the old (now replaced) document.

If the selector contains a _rev attribute, the method first checks that the specified revision is the current revision of that document. If not, there is a conflict, and an error is thrown.

collection.replace(selector, data, options)

As before, but options must be an object that can contain the following boolean attributes:

  • waitForSync: One can force synchronization of the document creation operation to disk even in case that the waitForSync flag is been disabled for the entire collection. Thus, the waitForSync option can be used to force synchronization of just specific operations. To use this, set the waitForSync parameter to true. If the waitForSync parameter is not specified or set to false, then the collection's default waitForSync behavior is applied. The waitForSync parameter cannot be used to disable synchronization for collections that have a default waitForSync value of true.
  • overwrite: If this flag is set to true, a _rev attribute in the selector is ignored.
  • returnNew: If this flag is set to true, the complete new document is returned in the output under the attribute new.
  • returnOld: If this flag is set to true, the complete previous revision of the document is returned in the output under the attribute old.
  • silent: If this flag is set to true, no output is returned.

db._replace(document-handle, data)

db._replace(document-handle, data, options)

As before. Instead of selector a document-handle can be passed as first argument. No revision precondition is tested.

Examples

Create and replace a document:

arangosh> a1 = db.example.insert({ a : 1 });
arangosh> a2 = db._replace(a1, { a : 2 });
arangosh> a3 = db._replace(a1, { a : 3 });
show execution results

Changes in 3.0 from 2.8:

The options silent, returnNew and returnOld are new.

Update

db._update(selector, data)

Updates an existing document described by the selector, which must be an object containing the _id attribute. There must be a document with that _id in the current database. This document is then patched with the data given as second argument. Any attribute _id, _key or _rev in data is ignored.

The method returns a document with the attributes _id, _key, _rev and _oldRev. The attribute _id contains the document handle of the updated document, the attribute _rev contains the document revision of the updated document, the attribute _oldRev contains the revision of the old (now updated) document.

If the selector contains a _rev attribute, the method first checks that the specified revision is the current revision of that document. If not, there is a conflict, and an error is thrown.

db._update(selector, data, options)

As before, but options must be an object that can contain the following boolean attributes:

  • waitForSync: One can force synchronization of the document creation operation to disk even in case that the waitForSync flag is been disabled for the entire collection. Thus, the waitForSync option can be used to force synchronization of just specific operations. To use this, set the waitForSync parameter to true. If the waitForSync parameter is not specified or set to false, then the collection's default waitForSync behavior is applied. The waitForSync parameter cannot be used to disable synchronization for collections that have a default waitForSync value of true.
  • overwrite: If this flag is set to true, a _rev attribute in the selector is ignored.
  • returnNew: If this flag is set to true, the complete new document is returned in the output under the attribute new.
  • returnOld: If this flag is set to true, the complete previous revision of the document is returned in the output under the attribute old.
  • silent: If this flag is set to true, no output is returned.
  • keepNull: The optional keepNull parameter can be used to modify the behavior when handling null values. Normally, null values are stored in the database. By setting the keepNull parameter to false, this behavior can be changed so that all attributes in data with null values will be removed from the target document.
  • mergeObjects: Controls whether objects (not arrays) will be merged if present in both the existing and the patch document. If set to false, the value in the patch document will overwrite the existing document's value. If set to true, objects will be merged. The default is true.

db._update(document-handle, data)

db._update(document-handle, data, options)

As before. Instead of selector a document-handle can be passed as first argument. No revision precondition is tested.

Examples

Create and update a document:

arangosh> a1 = db.example.insert({ a : 1 });
arangosh> a2 = db._update(a1, { b : 2 });
arangosh> a3 = db._update(a1, { c : 3 });
show execution results

Changes in 3.0 from 2.8:

The options silent, returnNew and returnOld are new.

Remove

db._remove(selector)

Removes a document described by the selector, which must be an object containing the _id attribute. There must be a document with that _id in the current database. This document is then removed.

The method returns a document with the attributes _id, _key and _rev. The attribute _id contains the document handle of the removed document, the attribute _rev contains the document revision of the removed eocument.

If the selector contains a _rev attribute, the method first checks that the specified revision is the current revision of that document. If not, there is a conflict, and an error is thrown.

db._remove(selector, options)

As before, but options must be an object that can contain the following boolean attributes:

  • waitForSync: One can force synchronization of the document creation operation to disk even in case that the waitForSync flag is been disabled for the entire collection. Thus, the waitForSync option can be used to force synchronization of just specific operations. To use this, set the waitForSync parameter to true. If the waitForSync parameter is not specified or set to false, then the collection's default waitForSync behavior is applied. The waitForSync parameter cannot be used to disable synchronization for collections that have a default waitForSync value of true.
  • overwrite: If this flag is set to true, a _rev attribute in the selector is ignored.
  • returnOld: If this flag is set to true, the complete previous revision of the document is returned in the output under the attribute old.
  • silent: If this flag is set to true, no output is returned.

db._remove(document-handle)

db._remove(document-handle, options)

As before. Instead of selector a document-handle can be passed as first argument. No revision check is performed.

Examples

Remove a document:

arangosh> a1 = db.example.insert({ a : 1 });
arangosh> db._remove(a1);
arangosh> db._remove(a1);
arangosh> db._remove(a1, {overwrite: true});
show execution results

Remove the document in the revision a1 with a conflict:

arangosh> a1 = db.example.insert({ a : 1 });
arangosh> a2 = db._replace(a1, { a : 2 });
arangosh> db._remove(a1);
arangosh> db._remove(a1, {overwrite: true} );
arangosh> db._document(a1);
show execution results

Remove a document using new signature:

arangosh> db.example.insert({ _key: "11265325374", a:  1 } );
arangosh> db.example.remove("example/11265325374",
........> { overwrite: true, waitForSync: false})
show execution results

Changes in 3.0 from 2.8:

The method now returns not only true but information about the removed document(s). The options silent and returnOld are new.