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Posted to issues@drill.apache.org by "Joel Bondurant (JIRA)" <ji...@apache.org> on 2016/09/14 17:49:20 UTC
[jira] [Commented] (DRILL-4826) Query against
INFORMATION_SCHEMA.TABLES degrades as the number of views increases
[ https://issues.apache.org/jira/browse/DRILL-4826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15491044#comment-15491044 ]
Joel Bondurant commented on DRILL-4826:
---------------------------------------
0: jdbc:drill:> 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;
+----------------+---------------+-------------+-------------+
| TABLE_CATALOG | TABLE_SCHEMA | TABLE_NAME | TABLE_TYPE |
+----------------+---------------+-------------+-------------+
+----------------+---------------+-------------+-------------+
No rows selected (534.714 seconds)
<facepalm/>
> 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: Parth Chandra
>
> 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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