Argthtjtr

Basically I am querying a view, requesting an update_seq value to be returned. I then use this returned sequence number in a subsequent _changes feed request. My expectation (which may be wrong?) is that the returned changes should be empty; since I just queried the view, and asking for changes since that view.

Normally this works fine, except when I update a document without changing its content (i.e. only the document's _rev field changes). Now I can query the view and changes as above, but it will always give a change result pointing to this changed document. Maybe the code below explains better ...

const request = require("request-promise-native");



const _throw = e => { throw e };



// Given an 'empty' couchdb database 'test' with the following design document:

//

// _id: "_design/test",

// language: "javascript",

//   views: {

//     test: {

//       map: function(doc) {

//         if (doc.message) emit(null, doc.message);

//       }

//     }

//   }



const db = "http://localhost:5984/test";



const get = id =>

  request.get({

    url: `${db}/${id}`,

    json: true,

  })



const post = body =>

  request.post({

    url: `${db}`,

    json: true,

    body

  });



// Insert doc, or update existing doc if it already exists ...

const update = doc =>

  get(doc._id)

    .then(({ _rev }) => post({ ...doc, _rev }))

    .catch(e => e.statusCode === 404 

      ? post(doc) 

      : _throw(e))



// Query the view, make sure to get the update_seq value ...

const messages = () => request

  .get({

    url: `${db}/_design/test/_view/test`,

    qs: { update_seq: true },

    json: true

  })



// Query the _changes feed for any changes since the supplied seq number

const changes = (since = "now") =>

  request

    .get({

      url: `${db}/_changes`,

      qs: { filter: "_view", view: "test/test", since },

      json: true

    })



// Just update the document, query the view, and then pass the returned seq to the changes feed ...

const check = async message => {

  await update({ _id: "test", message });

  const msgs = await messages();

  console.log("messages:", msgs.rows);

  const chgs = await changes(msgs.update_seq);

  console.log("changes:", chgs.results, "nn");

}



// I would expect the changes results to always be empty, since I am tracking the 

// changes since the seq number returned from the view (and there are no changes

// to the database inbetween). However, this is only true for when the message field

// of the document changes. Updating the doc without changing this field (i.e. just

// triggering a _rev change) causes the changes result to be always non-empty



const run_checks = async () => {

  await check("1");

  await check("1");

  await check("2");

  await check("2");

  await check("2");

}



run_checks();

This gives the following results:

$ node changes.js 

messages: [ { id: 'test', key: null, value: '1' } ]

changes:  





messages: [ { id: 'test', key: null, value: '1' } ]

changes: [ { seq:

     '55-g1AAAAH3eJzLYWBg4MhgTmEQTM4vTc5ISXIwNDLXMwBCwxygFFMiQ5L8____szKYExlygQLs5mlmqZamZikMnKV5KalpmXmpKXi0JykAySR7kAmJjPjUOYDUxaPalJpkYpZkTKxNCSAT6lFMSEqxSDM1NSXShDwWIMnQAKSAhsxHmJKaZGFoQLSPIaYsgJiyH2FKskmyhbm5CUmmHICYch9kihnER6ZpxuYgt2DqI2jaA4hpwJhgyAIAz9mJKQ',

    id: 'test',

    changes: [ [Object] ] } ] 





messages: [ { id: 'test', key: null, value: '2' } ]

changes:  





messages: [ { id: 'test', key: null, value: '2' } ]

changes: [ { seq:

     '57-g1AAAAH3eJzLYWBg4MhgTmEQTM4vTc5ISXIwNDLXMwBCwxygFFMiQ5L8____szKYExlygQLs5mlmqZamZikMnKV5KalpmXmpKXi0JykAySR7kAmJjPjUOYDUxaPalJpkYpZkTKxNCSAT6lFMSEqxSDM1NSXShDwWIMnQAKSAhsxHmJKaZGFoQLSPIaYsgJiyH2FKskmyhbm5CUmmHICYch9kigXER6ZpxuYgt2DqI2jaA4hpwJhgyAIA0HWJKw',

    id: 'test',

    changes: [ [Object] ] } ] 





messages: [ { id: 'test', key: null, value: '2' } ]

changes: [ { seq:

     '58-g1AAAAIzeJyV0EsOgjAQBuBRTNSlJ9ATGKAtbVdyE6WvIEFcsdab6E30JnoTLNYESAyBNJkmbebLP5MDwCL1FKzkuZSpEnEQ0q1vT5Dbr2kCYl1VVZZ6CZzsw5yaSHMSKViWhdLmWGjV0y42tordT5h8hZAxpHDyr6dPimtp382iBY4EGprlUAuXjiAUM4SQgUIxsxWu9rLIrVG0YIE_eCdOuTvl0SgSS0YpHqU8nfKqFe4mIgbROsuo7Trt7bTWfphUiPOwnSn7AHWel-8',

    id: 'test',

    changes: [ [Object] ] } ]

The changes result is only empty when the actual value in the view changes ... What am I missing?