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https://issues.apache.org/jira/browse/COUCHDB-3357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15955237#comment-15955237
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Garren Smith commented on COUCHDB-3357:
---------------------------------------
A very basic first attempt at a solution
https://github.com/apache/couchdb/pull/469
> Improve the way the index is chosen
> -----------------------------------
>
> Key: COUCHDB-3357
> URL: https://issues.apache.org/jira/browse/COUCHDB-3357
> Project: CouchDB
> Issue Type: Improvement
> Components: Mango
> Reporter: Garren Smith
>
> Currently if two or more indexes are able to be used for a query the
> choose_best_index can get in a position where it will chose the index based
> based on sort order of its dbname, ddocid. This isn't ideal.
> If we have two docs like this:
> doc1 = {
> name: "Mary"
> };
> doc2 = {
> name: "Mary",
> role: "Ceo"
> };
> If we create two indexes:
> Index 1 = fields: ['name', 'role']
> Index 2 = fields: ['name']
> And if we create a query like this:
> selector: {
> name: 'Mary'
> };
> If index 1 has a ddocId higher in the alphabet e.g A and Index 2 has a lower
> ddocId like Z. Then Index will be selected which means that doc 1 will be
> excluded.
> An example of a test case can be found here
> https://github.com/apache/couchdb/blob/7951c8ae498e372d0db19887c6e39a91885df4e1/src/mango/test/12-use-correct-index.py
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