[GitHub] alxndrsn opened a new pull request #541: Allow configuration of max doc IDs for optimised code path in changes filter

[gi...@git.apache.org]

alxndrsn opened a new pull request #541: Allow configuration of max doc IDs for optimised code path in changes filter
URL: https://github.com/apache/couchdb/pull/541
 
 
   ## Overview
   
   With certain data sets, performance of the `_changes` feed with the `doc_ids` filter falls off a cliff when the number of supplied `doc_ids` exceeds 100.
   
   This change allows configuration of the poor performance threshold:
   
   ### Previous default
   ```
   [changes]
   max_doc_ids = 100
   ```
   
   ### Always perform poorly
   ```
   [changes]
   max_doc_ids = 0
   ```
   
   ### Perform poorly when more than 10000 doc IDs are supplied
   ```
   [changes]
   max_doc_ids = 10000
   ```
   
   ## Testing recommendations
   
   Get a big dataset, and compare the performance of `_changes` requests with the `doc_ids` filter when:
   ```
   [changes]
   max_doc_ids = 0
   ```
   and
   ```
   [changes]
   max_doc_ids = 100
   ```
   with 100 or less doc_ids.
   
   ## Jira issue number
   
   Fixes https://issues.apache.org/jira/browse/COUCHDB-3425
   
   ## Related Pull Requests
   
   Just this one.
   
   ## Checklist
   
   - [ ] Code is written and works correctly;
   - [ ] Changes are covered by tests;
   - [ ] Documentation reflects the changes;
   
 
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