[DERBY-4710] Upgrade from 10.2 to 10.6 fails if existing database contains a large number of tables with similar names.

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 10.5.1.1, 10.5.2.0, 10.5.3.0, 10.6.1.0
• Component/s: SQL, Store
• Labels: derby_triage10_5_2 derby_triage10_9
• Environment: Windows XP SP3, or Windows Server 2003 R2 32-bit. Not tested on any other platform.
• Urgency: Normal
• Issue & fix info: Repro attached
• Bug behavior facts: Performance, Seen in production
• Assignee: Unassigned
• Reporter: Ray Gala
• Created: 23/Jun/10 00:14
• Updated: 22/Feb/12 02:49

Description

Upgrade fails because of quick degradation in performance when trying to upgrade our existing Derby DB from version 10.2.2 to the latest build 10.6. Problem is that our database contains thousands of tables with the names starting from "SURVEY_xxxxx" where xxxxx can be any integer from 1 to 99999. Upgrade fails on this tables to the point that one cannot access any of them, because apparently it takes a very long time to open them.

We staged a test in order to see how database handles creation of thousands of similarly named tables.

Below we will try to describe how the test was conducted.

Process

• Create a new blank database in 10.6

In a loop from 1 to 10000

{ although I only managed to get to 1510 over night}

• Created a program that creates a table called SURVEY_X

• Inserts 1/2 hour interval data from the range 2006-08-03 15:00:00 to 2009-01-15 00:00:00. 40,000 records.

And this process repeats.

Results

• At the start (10:00 pm) a single cycle of create and insert was taking 2 seconds i.e Creation of SURVEY_1

• Run overnight

• In the morning 7:00am it had only got to 1510 table and insert creations, and was taking 2 minutes for every new table - i.e Creation of SURVEY_1510

If I change the program (and use it on this database with the current 1510 tables in it) to create a table called T_SURVEY_X then it goes back to 2 seconds, although I suspect that if I left it running and we had 1500 tables called T_SURVEY_X we would have the same problem.

The symptom is also present in SQLWorkbench/J where it takes 2 seconds to see table T_SURVEY_0 but 45 seconds to see SURVEY_1510 and even after it presents the data it still seems to lock up etc.

So this explains why with 6000 tables that we seem to get no response at all. As you can see from the enclosed log performance starts really degrading after a 1000 tables.