mirror of https://gitee.com/bigwinds/arangodb
59 lines
2.3 KiB
Markdown
59 lines
2.3 KiB
Markdown
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@brief update a document
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`db._update(document, data, overwrite, keepNull, waitForSync)`
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Updates an existing *document*. The *document* must be a document in
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the current collection. This document is then patched with the
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*data* given as second argument. The optional *overwrite* parameter can
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be used to control the behavior in case of version conflicts (see below).
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The optional *keepNull* parameter can be used to modify the behavior when
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handling *null* values. Normally, *null* values are stored in the
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database. By setting the *keepNull* parameter to *false*, this behavior
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can be changed so that all attributes in *data* with *null* values will
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be removed from the target document.
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The optional *waitForSync* parameter can be used to force
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synchronization of the document update operation to disk even in case
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that the *waitForSync* flag had been disabled for the entire collection.
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Thus, the *waitForSync* parameter can be used to force synchronization
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of just specific operations. To use this, set the *waitForSync* parameter
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to *true*. If the *waitForSync* parameter is not specified or set to
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false*, then the collection's default *waitForSync* behavior is
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applied. The *waitForSync* parameter cannot be used to disable
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synchronization for collections that have a default *waitForSync* value
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of *true*.
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The method returns a document with the attributes *_id*, *_rev* and
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*_oldRev*. The attribute *_id* contains the document handle of the
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updated document, the attribute *_rev* contains the document revision of
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the updated document, the attribute *_oldRev* contains the revision of
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the old (now replaced) document.
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If there is a conflict, i. e. if the revision of the *document* does not
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match the revision in the collection, then an error is thrown.
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`db._update(document, data, true)`
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As before, but in case of a conflict, the conflict is ignored and the old
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document is overwritten.
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`db._update(document-handle, data)`
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As before. Instead of document a *document-handle* can be passed as
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first argument.
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@EXAMPLES
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Create and update a document:
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@EXAMPLE_ARANGOSH_OUTPUT{documentDocumentUpdate}
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~ db._create("example");
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a1 = db.example.insert({ a : 1 });
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a2 = db._update(a1, { b : 2 });
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a3 = db._update(a1, { c : 3 }); // xpError(ERROR_ARANGO_CONFLICT);
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~ db._drop("example");
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@END_EXAMPLE_ARANGOSH_OUTPUT
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