mirror of https://gitee.com/bigwinds/arangodb
68 lines
2.7 KiB
Plaintext
68 lines
2.7 KiB
Plaintext
!CHAPTER Data modification queries
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As of ArangoDB version 2.2, AQL supports the following
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data-modification operations:
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- INSERT: insert new documents into a collection
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- UPDATE: partially update existing documents in a collection
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- REPLACE: completely replace existing documents in a collection
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- REMOVE: remove existing documents from a collection
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Data-modification operations are normally combined with *FOR* loops to
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iterate over a given list of documents. They can optionally be combined with
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*FILTER* statements and the like.
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Let's start with an example that modifies existing documents in a collection
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*users* that match some condition:
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FOR u IN users
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FILTER u.status == 'not active'
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UPDATE u WITH { status: 'inactive' } IN users
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Note there is no need to combine a data-modification query with other
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AQL operations such as *FOR* and *FILTER*. For example, the following
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stripped-down *update* query will work, too. It will *update* one document
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(with key *foo*) in collection *users*:
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UPDATE "foo" WITH { status: 'inactive' } IN users
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Now, let's copy the contents of the collection *users* into the collection
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*backup*:
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FOR u IN users
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INSERT u IN backup
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As a final example, let's find some documents in collection *users* and
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remove them from collection *backup*. The link between the documents in both
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collections is establish via the documents' keys:
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FOR u IN users
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FILTER u.status == 'deleted'
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REMOVE u IN backup
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!SUBSECTION Restrictions
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The name of the modified collection (*users* and *backup* in the above cases)
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must be known to the AQL executor at query-compile time and cannot change at
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runtime. Using a bind parameter to specify the [collection name](../Glossary/README.html#collection_name) is allowed.
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Data-modification queries are restricted to modifying data in a single
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collection per query. That means a data-modification query cannot modify
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data in multiple collections with a single query. It is still possible (and
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was shown above) to read from one or many collections and modify data in another
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with one query.
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!SUBSECTION Transactional Execution
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On a single server, data-modification operations are executed transactionally.
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If a data-modification operation fails, any changes made by it will be rolled
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back automatically as if they never happened.
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In a cluster, AQL data-modification queries are currently not executed transactionally.
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Additionally, *update*, *replace* and *remove* AQL queries currently require the
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*_key* attribute to be specified for all documents that should be modified or
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removed, even if a shared key attribute other than *_key* was chosen for the
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collection. This restriction may be overcome in a future release of ArangoDB.
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