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Posted to derby-dev@db.apache.org by "Holger Rehn (Jira)" <ji...@apache.org> on 2021/03/20 21:18:00 UTC
[jira] [Updated] (DERBY-7109)
SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE doesn't work as expected
[ https://issues.apache.org/jira/browse/DERBY-7109?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Holger Rehn updated DERBY-7109:
-------------------------------
Description:
The SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE procedure seems to be unable to reclaim any disk space under almost all circumstances. I have a number of existing DBs that I tried to reorganize to reclaim disk space using the mentioned procedure. Because that didn't even free the smallest amount of space, I started a number of tests and it looks like inplace compression simply doesn't work, at all.
Example:
One of the DBs uses ~37 GB of disk space and the exact same amount after running SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE. After using SYSCS_UTIL.SYSCS_COMPRESS_TABLE to reorganize the DB it only uses 20,4 GB of disk space. This might be correct, if I correctly understand how inplace compression should work - but is not really what I expected. But even after I completely deleted a number of tables and removed more than 90% of the rows from all other tables of the original DB, SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE was unable to reclaim any disk space. In contrast, SYSCS_UTIL.SYSCS_COMPRESS_TABLE now reduced the DB size to ~ 130MB. To carry this to the extreme, I completely removed any data from all tables. As expected, procedure SYSCS_UTIL.SYSCS_COMPRESS_TABLE now results in an empty DB only taking up ~4 MB of disk space, while SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE was still unable to reclaim a relevant amount of disk space (only ~ 4,6GB), leaving a completely empty DB still occupying more than 32 GB of disk space.
was:
The SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE procedure seems to be unable to reclaim any disk space under almost all circumstances. I have a number of existing DBs that I tried to reorganize to reclaim disk space using the mentioned procedure. Because that didn't even free the smallest amount of space, I started a number of tests and it looks like inplace compression simply doesn't work, at all.
Example:
One of the DBs uses ~37 GB of disk space and the exact same amount after running SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE. After using SYSCS_UTIL.SYSCS_COMPRESS_TABLE to reorganize the DB it only uses 20,4 GB of disk space. This might be correct, if I correctly understand how inplace compression should work - but is not really what I expected. But even after I completely deleted a number of tables and removed more than 90% of the rows from all other tables of the original DB, SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE was unable to reclaim any disk space. In contrast, SYSCS_UTIL.SYSCS_COMPRESS_TABLE now reduced the DB size to ~ 130MB. To carry this to the extreme, I completely removed any data from all tables. As expected, procedure SYSCS_UTIL.SYSCS_COMPRESS_TABLE now results in an empty DB only taking up ~4 MB of disk space, while SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE was still unable to reclaim a relevant amount of disk space (only ~ 600MB), leaving a completely empty DB still occupying more than 30 GB of disk space.
> SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE doesn't work as expected
> ----------------------------------------------------------------
>
> Key: DERBY-7109
> URL: https://issues.apache.org/jira/browse/DERBY-7109
> Project: Derby
> Issue Type: Bug
> Components: Store
> Affects Versions: 10.14.2.0, 10.15.2.0
> Reporter: Holger Rehn
> Priority: Critical
>
> The SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE procedure seems to be unable to reclaim any disk space under almost all circumstances. I have a number of existing DBs that I tried to reorganize to reclaim disk space using the mentioned procedure. Because that didn't even free the smallest amount of space, I started a number of tests and it looks like inplace compression simply doesn't work, at all.
> Example:
> One of the DBs uses ~37 GB of disk space and the exact same amount after running SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE. After using SYSCS_UTIL.SYSCS_COMPRESS_TABLE to reorganize the DB it only uses 20,4 GB of disk space. This might be correct, if I correctly understand how inplace compression should work - but is not really what I expected. But even after I completely deleted a number of tables and removed more than 90% of the rows from all other tables of the original DB, SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE was unable to reclaim any disk space. In contrast, SYSCS_UTIL.SYSCS_COMPRESS_TABLE now reduced the DB size to ~ 130MB. To carry this to the extreme, I completely removed any data from all tables. As expected, procedure SYSCS_UTIL.SYSCS_COMPRESS_TABLE now results in an empty DB only taking up ~4 MB of disk space, while SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE was still unable to reclaim a relevant amount of disk space (only ~ 4,6GB), leaving a completely empty DB still occupying more than 32 GB of disk space.
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