[jira] [Commented] (COUCHDB-3357) Improve the way the index is chosen

["Garren Smith (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/COUCHDB-3357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15955237#comment-15955237 ] 

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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