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https://issues.apache.org/jira/browse/DRILL-5089?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15942161#comment-15942161
]
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_r108051710
--- 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 ) {
+ return false;
--- End diff --
Clearer would be:
```
return (now - lastCheck) < 1000;
```
And, the 1000 should be made into a constant:
```
public static int CACHED_SCHEMA_REFRESH_MS = 1000;
```
> 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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