[ http://issues.apache.org/jira/browse/DERBY-1002?page=all ]
Deepa Remesh updated DERBY-1002:
--------------------------------
Attachment: derby1002-patch1-draft1.diff
derby1002-patch1-draft1.status
Attaching a draft patch 'derby1002-patch1-draft1.diff'. This patch is only for
review.
Summary of patch:
* Adds reset() methods to DRDAStatement and DRDAResultSet objects. The purpose
of reset method is to reset the states of all variables so that the objects
can be re-used and will not have left-over states.
* In case of DRDAStatement, the following variables are not reset:
+ * 1. database - This variable gets initialized in the constructor and by
+ * call to setDatabase.
+ * 2. members which get initialized in setPkgnamcsn (pkgnamcsn, pkgcnstkn,
+ * pkgid, pkgsn, isolationLevel, cursorName). pkgnamcsn is the key used to
+ * find if the DRDAStatement can be re-used. Hence its value will not
change
+ * when the object is re-used.
* close() methods are changed to only close and dereference objects.
* DRDAStatement.rsClose() method is not used in close() or reset(). This method
has some checks which were causing the method to return without resetting
currentDrdaRs. Now, close() calls currentDrdaRs.close() and reset() calls
currentDrdaRs.reset().
* In Database.newDrdaStatement, close() method is called followed by reset()
when the server finds the statement can be re-used.
Initially, I was thinking reset should also call close methods for the jdbc
objects instead of just resetting them to null so that the jdbc objects get
cleaned up properly if just reset() is called. Any comments on how it is done
now? I was also thinking about calling reset at places where
DRDAStatement.initialize is currently called to re-use default statements. On
looking more into the code, I find default statements are different in the way
they get initialized and used. e.g: stmt variable used in default statement is
created only once in Database.makeConnection. I have to see the usage of
default statements to see what exactly it means to re-initialize them.
There are some TODO items identified in discussion with Knut and Kathey in the
following mail thread:
http://www.nabble.com/-DRDA-Question-about-DRDAStatement.initialize%28%29-method-t1177861.html
TODOs:
* Add the repro to test suite.
* pkgcnstkn, pkgid, pkgsn variables can be removed from DRDAStatement since
these are derived from pkgnamcsn object.
* Look into what is required by initialize() of default statement. Currently,
initialize just calls setTypDefValues().
I ran my repro with this patch. derbyall is not complete. I will update with
results of test run later. Please take a look at this patch. Thanks.
> Check that DRDAStatement and DRDAResultSet states are reset when they are
> re-used
> ---------------------------------------------------------------------------------
>
> Key: DERBY-1002
> URL: http://issues.apache.org/jira/browse/DERBY-1002
> Project: Derby
> Type: Bug
> Components: Network Server
> Reporter: Deepa Remesh
> Assignee: Deepa Remesh
> Fix For: 10.2.0.0
> Attachments: derby1002-patch1-draft1.diff, derby1002-patch1-draft1.status,
> derby1002.java
>
> Network server re-uses DRDAStatement and DRDAResultSet objects when client
> sends a request with same section number. When re-using DRDAStatement, it's
> close() method is called which inturn calls close() method of DRDAResultSet.
> For re-use to work properly, we have to ensure the states of these objects
> are reset. This is not a bug but it is an area for possible improvements like:
> * The reset of all states are not in the close() methods. The states get
> re-initialized at different places in the code. Fo example, in case of
> DRDAResultSet, they get initialized in some other DRDAStatement methods -
> like addResultSet, setRsDefaultOptions, setOPNQRYOptions, setQueryOptions
> etc. It will be good to have all resets in one method.
> * The method name "close" is confusing since it is also called when objects
> get re-used. For clarity, it may be good to have a method named reset(). And
> then have the close method call reset.
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