[I] Unwanted Change Emission After `GET` Request during `changesAsStream() [couchdb-nano]

["kuncevic (via GitHub)" <gi...@apache.org>]

kuncevic opened a new issue, #350:
URL: https://github.com/apache/couchdb-nano/issues/350

   I’m using **Nano v10.1.4** with **CouchDB 3.5.0** and observed unexpected behavior with [nano.db.changesAsStream()](https://github.com/apache/couchdb-nano?tab=readme-ov-file#nanodbchangesasstreamname-params)
   
   ## Steps to Reproduce:
   1. Subscribe to `changesAsStream()` with `doc_ids: ['xyz']`.
   2. Update document `xyz` via `POST`.
   3. Perform a `GET` on document `xyz`.
   4. The stream emits a change for `xyz` (expected).
   5. Immediately after, the stream emits `xyz` again — with the same `_rev` and content as you get with the `GET` in step 3 (a side effect here).
   
   ## Observations:
   - The **GET request** caused the document to be emitted again, even though the `_rev` did not change.
   - The second emission appears to be a side effect of the `GET` request.
   - If **step 3** (GET) is skipped, only the expected change is emitted.
     
   ## Expected Behavior:
   According to the [CouchDB _changes API](https://docs.couchdb.org/en/stable/api/database/changes.html), only **write operations** (`PUT`, `POST`, `DELETE`) should trigger events — not reads like `GET`.
   
   ## Connection Options:
   
   ```js
   const options: any = {
         since: 'now',
         feed: 'continuous',
         include_docs: true,
   };
   ```
   
   For example, with `feed: 'longpoll'`, the side effect does not occur, which is expected as longpoll closes the connection after the first event. I haven't tested other feed options yet.
   
   Just trying to get to the bottom of it. Any thoughts?


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Re: [I] Unwanted Change Emission After `GET` Request during changesAsStream() [couchdb-nano]

["glynnbird (via GitHub)" <gi...@apache.org>]

glynnbird commented on issue #350:
URL: https://github.com/apache/couchdb-nano/issues/350#issuecomment-2915686775

   I tried this with the latest CouchDB 3.5 and the latest Nano 10.1.4:
   
   ```js
   const Nano = require('nano')
   const nano = Nano(process.env.COUCH_URL)
   
   async function main() {
   
     const test = nano.db.use('test')
     const opts = {
       since: 'now',
       feed: 'continuous',
       include_docs: true
     }
     test.changesAsStream(opts).pipe(process.stdout)
   
   }
   main()
   ```
   
   Adding data:
   
   ```sh
   ccurl -X POST -d'{"a":1}' /test             
   {
     "ok": true,
     "id": "c77906581adaefba3eb6190c260025f3",
     "rev": "1-23202479633c2b380f79507a776743d5"
   }
   ```
   
   Edit data:
   
   ```sh
   ccurl -X POST -d'{"_id":"c77906581adaefba3eb6190c260025f3","_rev":"1-23202479633c2b380f79507a776743d5","a":2}' /test
   {
     "ok": true,
     "id": "c77906581adaefba3eb6190c260025f3",
     "rev": "2-71173597778497e0a6aa176963f222db"
   }
   ```
   
   Fetch data:
   
   ```sh
   ccurl /test/c77906581adaefba3eb6190c260025f3
   {
     "_id": "c77906581adaefba3eb6190c260025f3",
     "_rev": "2-71173597778497e0a6aa176963f222db",
     "a": 2
   }
   ```
   
   and I got two events:
   
   ```js
   {"seq":"15-g1AAAACbeJzLYWBgYMpgTmEQTM4vTc5ISXLIyU9OzMnILy7JAUklMiTV____PyuDOZEjFyjAnmJobmFslIpNAx5j8liAJEMDkPoPNY0dbJqRgaFpiqURNn1ZAF68MEo","id":"c77906581adaefba3eb6190c260025f3","changes":[{"rev":"1-23202479633c2b380f79507a776743d5"}],"doc":{"_id":"c77906581adaefba3eb6190c260025f3","_rev":"1-23202479633c2b380f79507a776743d5","a":1}}
   
   {"seq":"16-g1AAAACbeJzLYWBgYMpgTmEQTM4vTc5ISXLIyU9OzMnILy7JAUklMiTV____PyuDOZEjFyjAnmJobmFslIpNAx5j8liAJEMDkPqPYpqRgaFpiqURNn1ZAF7eMEs","id":"c77906581adaefba3eb6190c260025f3","changes":[{"rev":"2-71173597778497e0a6aa176963f222db"}],"doc":{"_id":"c77906581adaefba3eb6190c260025f3","_rev":"2-71173597778497e0a6aa176963f222db","a":2}}
   ```
   
   one for the insert, and one for the update. 
   
   Fetching a document does not trigger a changes feed event in CouchDB, and Nano is simply doing a CouchDB changes feed request without any magic.
   
   I should point out that the CouchDB promises to deliver each change _at least once_ not _only once_. 


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Re: [I] Unwanted Change Emission After `GET` Request during changesAsStream() [couchdb-nano]

["glynnbird (via GitHub)" <gi...@apache.org>]

glynnbird closed issue #350: Unwanted Change Emission After `GET` Request during changesAsStream()
URL: https://github.com/apache/couchdb-nano/issues/350


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