MarkLogic Node.js按“最后修改"排序 [英] MarkLogic Node.js Sort on "last-modified"

问题描述

我想按元数据属性"最后修改"对文档进行排序.我已经在"last-modified"上创建了element-range-index，并在管理面板中为数据库启用了选项"保持上次修改".但是，当我在Node.js中运行以下语句时，

I want to sort the documents by metadata property "last-modified". I have already created element-range-index on "last-modified" and also enabled option "maintain last modified" in Admin Panel for the database.But, when I run below statement in Node.js

return db.documents.query(
        qb.where().orderBy(qb.sort("last-modified")).slice(from, length)).result();

我遇到了错误.请帮忙吗?

I am getting below error. Please help?

 Error { [Error: query documents: response with invalid 400 status]
  message: 'query documents: response with invalid 400 status',
  statusCode: 400,
  body:
   { errorResponse:
      { statusCode: 400,
        status: 'Bad Request',
        messageCode: 'SEARCH-BADORDERBY',
        message: 'SEARCH-BADORDERBY: (err:FOER0000) Indexes are required to supp
ort element, element-attribute, json-property, or field sort specifications.' }
} }

推荐答案

更新:阐明了片段说明；固定示例

last-modified属性(由maintain last modified设置控制)不是存储在文档本身中，而是存储在文档属性，这是与每个文档关联的元数据片段.在MarkLogic Node.js API中，您可以使用 qb.documentFragment() 或 qb.propertiesFragment() .

The last-modified property (controlled by the maintain last modified setting) is not stored in the document itself, but in the document properties, which is a metadata fragment associated with each document. In the MarkLogic Node.js API, you can constrain queries to the document or the document properties with qb.documentFragment() or qb.propertiesFragment().

但是，您只能按返回数据的各个方面进行排序:默认情况下，文档本身.您可以使用 qb.fragmentScope() 来指定查询返回documents还是properties .

However, you can only sort by aspects of the data you are returning: by default, the document itself. You can specify that your query return either documents or properties using qb.fragmentScope().

注意:文档属性以XML格式存储在http://marklogic.com/xdmp/property命名空间中，因此您的element-range-index也必须使用该命名空间.

Note: Document properties are stored as XML in the http://marklogic.com/xdmp/property namespace, so your element-range-index must also use that namespace.

以下是获取10个最新文档属性的方法:

Here's how you would get the 10 most-recent document properties:

return db.documents.query(
  qb.where(
    qb.fragmentScope('properties')
  ).orderBy(
    qb.sort(
      qb.element(qb.qname('http://marklogic.com/xdmp/property', 'last-modified')),
      'descending'
    )
  ).slice(1, 10))
.result();

您可以通过将文档本身与qb.documentFragment()匹配的任何查询来进一步限制这些结果:

You could further restrict these results by any query matching the document itself with qb.documentFragment():

假定test上的int范围索引:

assuming an int range index on test:

return db.documents.query(
  qb.where(
    qb.fragmentScope('properties'),
    qb.documentFragment(
      qb.range( qb.element('test'), '<', 20 )
    )
  ).orderBy(
    qb.sort(
      qb.element(qb.qname('http://marklogic.com/xdmp/property', 'last-modified')),
      'descending'
    )
  ).slice(1, 10))
.result();

最后，如果要获取文档本身而不是其属性，则可以使用查询所检索的文档URI向db.documents.read()发出请求:

Finally, if you want to then get the documents themselves, and not their properties, you could make a request to db.documents.read(), with the document URIs retrieved by the query:

注意:以下示例使用lodash/下划线

return db.documents.query(
  qb.where(
    qb.fragmentScope('properties'),
    qb.documentFragment(
      qb.range( qb.element('test'), '<', 20 )
    )
  ).orderBy(
    qb.sort(
      qb.element(qb.qname('http://marklogic.com/xdmp/property', 'last-modified')),
      'descending'
    )
  ).slice(1, 10))
.result(function(documents) {
  db.documents.read(
    _.map(documents, 'uri')
  ).result(function(documents) {
    _.each(documents, function(doc) { console.log(doc.content); })
  });
});

或者，您的应用程序可以直接在文档中维护last-modified属性，在这种情况下，您的查询会简单得多:

Alternately, your application could maintain a last-modified property directly in your documents, in which case your query can be much simpler:

return db.documents.query(
  qb.where(
    qb.range( qb.element('test'), '<', 20 )
  ).orderBy(
    qb.sort( qb.element('last-modified'), 'descending' )
  ).slice(1, 10))
.result(function(documents) {
  _.each(documents, function(doc) { console.log(doc.content); })
});

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