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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-5089) Skip initializing all enabled storage plugins for every query
Date Sun, 26 Mar 2017 05:46:43 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5089?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15942154#comment-15942154
] 

ASF GitHub Bot commented on DRILL-5089:
---------------------------------------

Github user paul-rogers commented on a diff in the pull request:

    https://github.com/apache/drill/pull/795#discussion_r108051696
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/AbstractSchema.java
---
    @@ -198,6 +200,10 @@ public Expression getExpression(SchemaPlus parentSchema, String name)
{
     
       @Override
       public boolean contentsHaveChangedSince(long lastCheck, long now) {
    +    //use cached schema for 1 second, it will be helpful if it is highly concurrent scenario
    +    if( abs(now - lastCheck) < 1000 ) {
    --- End diff --
    
    You want to check if either now is one second in the future -- or one second in the past?
Under what conditions would lastCheck - now be negative and so would need an abs?


> Skip initializing all enabled storage plugins for every query
> -------------------------------------------------------------
>
>                 Key: DRILL-5089
>                 URL: https://issues.apache.org/jira/browse/DRILL-5089
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Query Planning & Optimization
>    Affects Versions: 1.9.0
>            Reporter: Abhishek Girish
>            Assignee: Chunhui Shi
>            Priority: Critical
>
> In a query's lifecycle, at attempt is made to initialize each enabled storage plugin,
while building the schema tree. This is done regardless of the actual plugins involved within
a query. 
> Sometimes, when one or more of the enabled storage plugins have issues - either due to
misconfiguration or the underlying datasource being slow or being down, the overall query
time taken increases drastically. Most likely due the attempt being made to register schemas
from a faulty plugin.
> For example, when a jdbc plugin is configured with SQL Server, and at one point the underlying
SQL Server db goes down, any Drill query starting to execute at that point and beyond begin
to slow down drastically. 
> We must skip registering unrelated schemas (& workspaces) for a query. 



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