Thanks for the extra information, Gerrit. I don't have any theories
about why the primary key and EVENT_LOG_ENTRY_TIME_CREATED_INDEX are
failing to compress. I don't have any better suggestion than the following:
1) Run SYSCS_DIAG.SPACE_TABLE() before and after
2) If you notice that Derby is failing to compress those two indexes
again, look in derby.log for errors or other diagnostics which may
provide some clues.
On 9/19/20 1:51 AM, Hohl, Gerrit wrote:
I'm sorry, I noticed that only replied to Rick. 😅
Von: Hohl, Gerrit
Gesendet: Mittwoch, 16. September 2020 09:21
An: Rick Hillegas <rick.hille...@gmail.com>
Betreff: AW: Indexes grow over time insanly big and can't be shrunk
thanks for your reply.
A1) SELECT * FROM TABLE(SYSCS_DIAG.SPACE_TABLE()) AS x WHERE (x.TABLEID =
CONGLOMERATENAME |ISIND&|NUMALLOCATEDPAGES |NUMFREEPAGES
|NUMUNFILLEDPAGES |PAGESIZE |ESTIMSPACESAVING |TABLEID
EVENT_LOG_ENTRY |0 |1186 |115
|1 |32768 |3768320
SQL190118123711680 |1 |1220394 |0
|1190424 |4096 |0
EVENT_LOG_ENTRY_LOG_NAME_INDEX |1 |245 |151
|115 |4096 |618496
EVENT_LOG_ENTRY_SOURCE_INDEX |1 |437 |177
|241 |4096 |724992
EVENT_LOG_ENTRY_TIME_CREATED_INDEX |1 |2032376 |0
|1965938 |4096 |0
EVENT_LOG_ENTRY_LOG_LEVEL_INDEX |1 |181 |134
|76 |4096 |548864
EVENT_LOG_ENTRY_USER_NAME_INDEX |1 |258 |208
|113 |4096 |851968
A2) CALL SYSCS_UTIL.SYSCS_COMPRESS_TABLE('app', 'event_log_entry', 1);
That command is only issued if the cumulated ESTIMSPACESAVING for the table and
its indexes is greater than 0.
But I'm not sure if Derby really reorganised the both problem indexes - namely
SQL190118123711680 (primary key) and EVENT_LOG_ENTRY_TIME_CREATED_INDEX -
because there was nothing to free.
At the point I got that information the compress command also may have failed
because there wasn't enough space left.
But I think it doesn't matter because before there was enough disk space and at
that time the index was already growing.
Means none of the previous executions was able to reorganize those 2 indexes
also there was enough space back then.
A3) Not sure what you mean with "pattern of activity", but we simply have a lot of
"INSERT INTO event_log_entry (...) VALUES (...)" statements.
At the start of the application there is also a "SELECT COUNT(*) FROM
event_log_entry" to get the current number of entries.
From the on the application keeps track of it internally.
If 10.000 entries are reached, for each entry which exceeds that number,
another entry is deleted (means the oldest). Those actions can also overlap.
Here the DDL of the table and its indexes:
CREATE TABLE event_log_entry (
id INTEGER NOT NULL PRIMARY KEY GENERATED ALWAYS AS IDENTITY (START WITH 1,
INCREMENT BY 1),
CREATE INDEX event_log_entry_log_name_index ON event_log_entry (log_name);
CREATE INDEX event_log_entry_source_index ON event_log_entry (source); CREATE
INDEX event_log_entry_time_created_index ON event_log_entry (time_created);
CREATE INDEX event_log_entry_log_level_index ON event_log_entry (log_level);
CREATE INDEX event_log_entry_user_name_index ON event_log_entry (user_name);
I already repaired it by dropping the indexes and recreating them (as I wrote
in my mail).
Now everything is working perfectly again.
But that doesn't mean that it won't happen again, of course. 😉
Von: Rick Hillegas <rick.hille...@gmail.com>
Gesendet: Dienstag, 15. September 2020 17:27
An: Derby Discussion <email@example.com>; Hohl, Gerrit <g.h...@aurenz.de>
Betreff: Re: Indexes grow over time insanly big and can't be shrunk
I don't have a theory about what caused this problem. Maybe
COMPRESS_TABLE() has a serious bug. A couple questions:
Q1) Do you have the results of SPACE_TABLE() for this situation?
Q2) What value did you specify for the SEQUENTIAL argument of COMPRESS_TABLE()?
Q3) Other than COMPRESS_TABLE(), what is the pattern of activity on this table?
If this happens again, take a look at the ALTER TABLE DROP PRIMARY KEY and
ALTER TABLE ADD CONSTRAINT commands. They may make it simpler to repair the
On 9/15/20 5:14 AM, Hohl, Gerrit wrote:
we use Apache Derby v10.14.2.0 in our software and now have a problem with an
Every night we perform a compact on all tables - at least the ones which can be
shrunk (SYSCS_DIAG.SPACE_TABLE() and SYSCS_UTIL.SYSCS_COMPRESS_TABLE(String,
Normally that constellation works fine.
But now faced an installation which ran out of free disk space without any
After some analysing we narrowed it down to one table which is meant for
Records are inserted and deleted often (the size of it is limited at 10.000
entries through the software).
The maximum - based on the structure - should be around 40 MB. Not really much.
So we were very surprised seeing that this thing took around 14 GB.
I realized that I accumulated the table and its indexes to get that value.
After splitting it up, I saw that the table itself really only took 40 MB.
But two of the 6 indexes - one was the primary key index - took more than 13 GB
Apache Derby also said no NUMFREEPAGES and no ESTIMSPACESAVING.
My solution then was shutting down the service (in-process database), connect
to the database, dropping the indexes, create a new column for temporarily
storing the primary key value, copying the values, also dropping that column,
recreating the primary key column, copying everything back, dropping the
temporary primary key column, creating all the indexes again.
Now everything is back to normal and the table *including* its indexes is 40 MB.
Any idea on this? Why did the index grow that big? What can I do preventing it?
Seems reorganising isn't an option as Apache Derby itself doesn't realize that
it can free space.