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Indexes: Indexing Attachments
Syntax
Using AttachmentsFor()
The AttachmentsFor method returns information about each attachment that extends
a specified document, including their names, sizes, and content type. write index definition as string.
IEnumerable<AttachmentName> AttachmentsFor(object doc);private String name;
private String hash;
private String contentType;
private long size;The AttachmentsFor method is available in AbstractIndexCreationTask.
Using LoadAttachment()/LoadAttachments()
LoadAttachment() loads an attachment to the index by document and attachment name.
LoadAttachments() loads all the attachments of a given document.
public IAttachmentObject LoadAttachment(object doc, string name);
public IEnumerable<IAttachmentObject> LoadAttachments(object doc);| Parameter | Type | Description |
|---|---|---|
| doc | A server-side document, an entity | The document whose attachments you want to load |
| name | String |
The name of the attachment you want to load |
GetContentAs Methods
To access the attachment content itself, use GetContentAsStream(). To
convert the content into a string, use GetContentAsString() with
the desired character encoding.
public Stream GetContentAsStream();
public string GetContentAsString(Encoding encoding);
public string GetContentAsString(); // Default: UTF-8Applications for Attachment Content: Machine Learning
Access to the attachment content opens the door to many different applications, including many that can be integrated directly into RavenDB.
In this blog post,
Oren Eini demonstrates how machine learning image recognition can be
added to an index using the additional sources
feature. The resulting index allows filtering and querying based on
image content.
Examples
Indexes with AttachmentsFor()
public static class Employees_ByAttachmentNames extends AbstractIndexCreationTask {
public Employees_ByAttachmentNames() {
map = "from e in docs.Employees\n" +
"let attachments = AttachmentsFor(e)\n" +
"select new {\n" +
" attachmentNames = attachments.Select(x => x.Name).ToArray()\n" +
"}";
}
}Indexes with LoadAttachment()
private class Companies_With_Attachments_JavaScript extends AbstractJavaScriptIndexCreationTask {
public Companies_With_Attachments_JavaScript() {
setMaps(Collections.singleton(
"map('Companies', function (company) {\n" +
" var attachment = LoadAttachment(company, company.ExternalId);\n" +
" return {\n" +
" CompanyName: company.Name,\n" +
" AttachmentName: attachment.Name,\n" +
" AttachmentContentType: attachment.ContentType,\n" +
" AttachmentHash: attachment.Hash,\n" +
" AttachmentSize: attachment.Size,\n" +
" AttachmentContent: attachment.getContentAsString('utf8')\n" +
" }\n"+
"});"
)
);
}
}Indexes with LoadAttachments()
private class Companies_With_All_Attachments_JS extends AbstractJavaScriptIndexCreationTask {
public Companies_With_All_Attachments_JS() {
setMaps(Collections.singleton(
"map('Companies', function (company) {\n" +
" var attachments = LoadAttachments(company);\n" +
" return attachments.map(attachment => ({\n" +
" AttachmentName: attachment.Name,\n" +
" AttachmentContent: attachment.getContentAsString('utf8')\n" +
" }));\n" +
"})"
)
);
}
}Querying the Index
//return all employees that have an attachment called "cv.pdf"
List<Employee> employees = session.query(Employees_ByAttachmentNames.class)
.containsAny("attachmentNames", Arrays.asList("employees_cv.pdf"))
.selectFields(Company.class, "cv.pdf").ofType(Employee.class)
.toList();
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