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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4826) Query against INFORMATION_SCHEMA.TABLES degrades as the number of views increases
Date Thu, 13 Oct 2016 22:33:20 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15573420#comment-15573420
] 

ASF GitHub Bot commented on DRILL-4826:
---------------------------------------

Github user ppadma commented on a diff in the pull request:

    https://github.com/apache/drill/pull/592#discussion_r83324461
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/ischema/InfoSchemaRecordGenerator.java
---
    @@ -290,28 +290,30 @@ public Tables(OptionManager optionManager) {
           return new PojoRecordReader<>(Records.Table.class, records.iterator());
         }
     
    -    @Override
    -    public void visitTables(String schemaPath, SchemaPlus schema) {
    +    @Override public void visitTables(String schemaPath, SchemaPlus schema) {
    --- End diff --
    
    why this change ?


> Query against INFORMATION_SCHEMA.TABLES degrades as the number of views increases
> ---------------------------------------------------------------------------------
>
>                 Key: DRILL-4826
>                 URL: https://issues.apache.org/jira/browse/DRILL-4826
>             Project: Apache Drill
>          Issue Type: Bug
>            Reporter: Parth Chandra
>            Assignee: Padma Penumarthy
>
> Queries against INFORMATION_SCHEMA.TABLES and INFORMATION_SCHEMA.VIEWS slow down as the
number of views increases. 
> BI tools like Tableau issue a query like the following at connection time:
> {code}
> select TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE from INFORMATION_SCHEMA.`TABLES`
WHERE TABLE_CATALOG LIKE 'DRILL' ESCAPE '\' AND TABLE_SCHEMA <> 'sys' AND TABLE_SCHEMA
<> 'INFORMATION_SCHEMA'ORDER BY TABLE_TYPE, TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME
> {code}
> The time to query the information schema tables degrades as the number of views increases.
On a test system:
> || Views || Time(secs) ||
> |500 | 6 |
> |1000 | 19 |
> |1500 | 33 |
> This can result in a single connection taking more than a minute to establish.
> The problem occurs because we read the view file for every view and this appears to take
most of the time.
> Querying information_schema.tables does not, in fact, need to open the view file at all,
it merely needs to get a listing of the view files. Eliminating the view file read will speed
up the query tremendously.



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