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https://issues.apache.org/jira/browse/DERBY-4314?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lily Wei updated DERBY-4314:
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Attachment: DERBY-4314-7-withoutpiggybacking.diff
This is the version I intent to submit for this fix.
This fix avoid assertion like DERBY-4343 by short-circuiting
setTransactionIsolation.
For case as users obtaining the pooled connection for the third time, the
variable
isolation_ is reset Connection.completeReset. If users call
setTransactionIsolation and executed, the server does not send any piggybacking
update because the isolation level has not changed.
Isolation_ remain as UNKNOWN until getTransactionIsolation is called
or a different statement causing a change of the isolation level
is executed. As mention before, we should think about change this to
READ_UNCOMMITTED.
With introducing getTransactionIsolationX and assertion is never reach.
Therefore, no assertion.
The client driver acts as embedded as without commit action when
setTransactionIsolation is called.
Performance concern: This fix does not improve performance, it will just move
the server round-trip. In some cases performance will be worse for the initial
setTransactionIsolation call, depending on
whether isolation_ value being set to READ_COMMITTED or not. If it is, one
round-trip (check + short-circuit). If it is not, two round-trip (check +
change).
I don't fully understand piggybacking. Any suggestion is welcome. I simply
think this is a good place to address this bug and DERBY-4343. I will
suggestion to open a new JIRA for the performance concern.
I run suits.all and derbyall.
> With derby client setTransactionIsolation executes and commits even if
> isolation has not changed
> -------------------------------------------------------------------------------------------------
>
> Key: DERBY-4314
> URL: https://issues.apache.org/jira/browse/DERBY-4314
> Project: Derby
> Issue Type: Improvement
> Components: JDBC, Network Client
> Affects Versions: 10.1.3.1, 10.2.2.0, 10.3.3.0, 10.4.2.0, 10.5.1.1,
> 10.6.1.0
> Reporter: Kathey Marsden
> Priority: Minor
> Attachments: DERBY-4314-2.diff, DERBY-4314-3.diff, DERBY-4314-5.diff,
> derby-4314-6a-initial_piggybacking.diff,
> derby-4314-6a-initial_piggybacking.stat,
> DERBY-4314-6b-combinepiggybacking.diff, DERBY-4314-6c-combineaftermerge.diff,
> derby-4314-6d-handle_xa.diff, DERBY-4314-7-withoutpiggybacking.diff,
> DERBY-4314.diff, ReproIsoLost.java, TestConnReuse.java, utilXid.java
>
>
> With in EmbedConnection.setIsolation() we have a check to see if the
> isolation level is the same and if so just return without doing a commit:
> public void setTransactionIsolation(int level) throws SQLException {
> if (level == getTransactionIsolation())
> return;
> with org.apache.derby.client.am.Connection we have no such check. It would be
> good if the client driver acted like embedded.
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