[jira] [Commented] (COUCHDB-3307) Limit calls to maybe_add_sys_db_callbacks to once per db open

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    [ https://issues.apache.org/jira/browse/COUCHDB-3307?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15890517#comment-15890517 ] 

ASF subversion and git services commented on COUCHDB-3307:
----------------------------------------------------------

Commit 8fc85c8653dcec640717d8a51ea29a28194cbe4a in couchdb-couch's branch refs/heads/2971-count-distinct from brkolla
[ https://git-wip-us.apache.org/repos/asf?p=couchdb-couch.git;h=8fc85c8 ]

Add sys db callbacks only once per db open

Currently we are adding the sys db callbacks for every request instead of
once while opening the db. This fix will ensure that we will only add the
sys db call backs once while opening the db.

COUCHDB-3307


> Limit calls to maybe_add_sys_db_callbacks to once per db open
> -------------------------------------------------------------
>
>                 Key: COUCHDB-3307
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-3307
>             Project: CouchDB
>          Issue Type: Bug
>          Components: Database Core
>            Reporter: Bala Kolla
>
> As part of performance regression testing we found out that there was a code change in 
>             {{couch_server:open/2,}}
>             {{Options = maybe_add_sys_db_callbacks(DbName, Options0)}}
> and as a result of that change, we are basically calling {{maybe_add_sys_db_callbacks}} for each request instead of once per db open.
> We have tested a fix to ensure that we call {{maybe_add_sys_db_callbacks}} only once per db open. And executed a GET performance benchmark and found the following improvements.
> * Throughput: Up to ~5% improvement.
> * Up to ~22% improvement in p90 and p99 latencies



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