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https://issues.apache.org/jira/browse/DERBY-1482?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mamta A. Satoor updated DERBY-1482:
-----------------------------------
Attachment: derby1482_patch5_stat.txt
derby1482_patch5_diff.txt
Attaching a new patch derby1482_patch5_diff.txt which takes care of the upgrade
problems which I ran into with the earlier draft patch.
During an upgrade(soft/hard), the trigger action SPSes get marked invalid and
hence when they fire next time, they will be regenerated and recompiled. The
issue with the earlier patch was that when in soft-upgrade mode, the patch was
using the new code to do the column read optimization while generating the
internal trigger action sql but when such a database goes back to it's original
version, the generated trigger action sql won't work anymore because previous
releases of Derby do not recognize this column read optimization. In order to
fix this, the code has to be smart to see if it is working with a pre-10.9
database(which in other words means that we are in soft-upgrade mode) and if
yes, then it should not use the column read optimization code during trigger
action SPS regeneration and during UPDATE execution when we read limited
columns from the trigger table based on what is required by the UPDATE sql and
the firing triggers I have made that change in the attached patch and now
the upgrade tests work fine. I have also run the complete junit suite and it
ranfine. derbyall is still running on my machine.
I will go ahead and commit this patch on Monday if there are no comments.
> Update triggers on tables with blob columns stream blobs into memory even
> when the blobs are not referenced/accessed.
> ---------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-1482
> URL: https://issues.apache.org/jira/browse/DERBY-1482
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.2.1.6
> Reporter: Daniel John Debrunner
> Assignee: Mamta A. Satoor
> Priority: Minor
> Labels: LOB
> Fix For: 10.7.1.1
>
> Attachments: DERBY_1482_patch4_diff.txt, DERBY_1482_patch4_stat.txt,
> TriggerTests_ver1_diff.txt, TriggerTests_ver1_stat.txt,
> derby1482DeepCopyAfterTriggerOnLobColumn.java, derby1482Repro.java,
> derby1482ReproVersion2.java, derby1482_patch1_diff.txt,
> derby1482_patch1_stat.txt, derby1482_patch2_diff.txt,
> derby1482_patch2_stat.txt, derby1482_patch3_diff.txt,
> derby1482_patch3_stat.txt, derby1482_patch5_diff.txt,
> derby1482_patch5_stat.txt, junitUpgradeTestFailureWithPatch1.out
>
>
> Suppose I have 1) a table "t1" with blob data in it, and 2) an UPDATE trigger
> "tr1" defined on that table, where the triggered-SQL-action for "tr1" does
> NOT reference any of the blob columns in the table. [ Note that this is
> different from DERBY-438 because DERBY-438 deals with triggers that _do_
> reference the blob column(s), whereas this issue deals with triggers that do
> _not_ reference the blob columns--but I think they're related, so I'm
> creating this as subtask to 438 ]. In such a case, if the trigger is fired,
> the blob data will be streamed into memory and thus consume JVM heap, even
> though it (the blob data) is never actually referenced/accessed by the
> trigger statement.
> For example, suppose we have the following DDL:
> create table t1 (id int, status smallint, bl blob(2G));
> create table t2 (id int, updated int default 0);
> create trigger tr1 after update of status on t1 referencing new as n_row
> for each row mode db2sql update t2 set updated = updated + 1 where t2.id =
> n_row.id;
> Then if t1 and t2 both have data and we make a call to:
> update t1 set status = 3;
> the trigger tr1 will fire, which will cause the blob column in t1 to be
> streamed into memory for each row affected by the trigger. The result is
> that, if the blob data is large, we end up using a lot of JVM memory when we
> really shouldn't have to (at least, in _theory_ we shouldn't have to...).
> Ideally, Derby could figure out whether or not the blob column is referenced,
> and avoid streaming the lob into memory whenever possible (hence this is
> probably more of an "enhancement" request than a bug)...
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