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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4526) A query (bug1) or a view (bug2) from a smaller db is at least order of magnitude slower than from a larger db despite indexes; the smalller db stores a subset of data stored in the larger db; the databases were created using the same script.
Date Wed, 27 Jan 2010 16:42:34 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12805565#action_12805565
] 

Knut Anders Hatlen commented on DERBY-4526:
-------------------------------------------

It looks like there are some files missing in the zip files:

1) The BugDemo class refers to a DerbyDb class that's not included, so it doesn't compile.

2) When I try to boot the databases in ij, I get this error message: ERROR XBM04: Collator
support not available from the JVM for the database's locale 'en_US_caseinsensitive'.

> A query (bug1) or a view (bug2) from a smaller db is at least order of magnitude slower
than from a larger db despite indexes; the smalller db stores a subset of data stored in the
larger db; the databases were created using the same script.
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-4526
>                 URL: https://issues.apache.org/jira/browse/DERBY-4526
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.5.3.0
>         Environment: see sysinfo.txt in the attachment
>            Reporter: Phil Michnik
>         Attachments: DERBY-4526 Bug Attachment.z01, DERBY-4526 Bug Attachment.z02, DERBY-4526
Bug Attachment.z03, DERBY-4526 Bug Attachment.z04, DERBY-4526 Bug Attachment.z05, DERBY-4526
Bug Attachment.z06, DERBY-4526 Bug Attachment.z07, DERBY-4526 Bug Attachment.z08, DERBY-4526
Bug Attachment.z09, DERBY-4526 Bug Attachment.z10, DERBY-4526 Bug Attachment.zip
>
>
> See BugDemo.java in the attachment. Below is a code snippet. 
> 	public BugDemo()
> 	{
> 		/*
> 		 * BUG 1: Although Derby uses indexes, "Hash table size = 31416" (see small_derby1.log)
is the suspect in case of small_db
> 		 */
> 		String sql = "select f.file_id, f.name, f.is_directory from Files f, FileRestorePoints
p where p.file_id=f.file_id"
> 					+" and p.restore_point_id=1 and f.parent_folder_id=?";
> 		demo("Bug1", large_db, sql); //no problem, 96547 rows, 8312 milliseconds on my PC
> 		demo("Bug1", small_db, sql); //too slow, 31416 rows, 504703 milliseconds on my PC,
see small_derby1.log in the attachment
> 		
> 		/*
> 		 * BUG 2: Derby ignores indexes on table FileRestorePoints or rpTable when selecting
from view 'rpView' of small_db on tables
> 		 * ('Files', 'FileRestorePoints', and 'rpTable') although indexes were created on each
of the tables;
> 		 * 
> 		 *  but, in case of large_db, indexes are used properly (both databases were created
from the same script)
> 		 */
> 		sql = "select file_id, name, length, is_directory from rpView where parent_folder_id=?";
> 		demo("Bug2", large_db, sql); //no problem, 96547 rows, 13718 milliseconds on my PC
> 		demo("Bug2", small_db, sql); //too slow, 31416 rows, 204110 milliseconds on my PC,
see small_derby2.log in the attachment
> 	}

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