Hello.
I could reproduce DERBY-318.
[EMAIL PROTECTED] :
-------
com.ibm.db2.jcc.c.DisconnectException: A communication error has been
detected.
Communication protocol being used: Reply.fill(). Communication API being
used: I
nputStream.read(). Location where the error was detected: insufficient data.
Com
munication function detecting the error: *. Protocol specific error codes(s)
TCP
/IP SOCKETS
at com.ibm.db2.jcc.a.a.a(a.java:426)
at com.ibm.db2.jcc.a.bb.b(bb.java:202)
com.ibm.db2.jcc.c.DisconnectException: A communication error has been
detected.
Communication protocol being used: Reply.fill(). Communication API being
used: I
nputStream.read(). Location where the error was detected: insufficient data.
Com
munication function detecting the error: *. Protocol specific error codes(s)
TCP
/IP SOCKETS
at com.ibm.db2.jcc.a.a.a(a.java:426)
at com.ibm.db2.jcc.a.bb.b(bb.java:202)
at com.ibm.db2.jcc.a.bb.c(bb.java:222)
at com.ibm.db2.jcc.a.bb.d(bb.java:236)
at com.ibm.db2.jcc.a.eb.a(eb.java:1911)
at com.ibm.db2.jcc.a.fb.a(fb.java:134)
at com.ibm.db2.jcc.a.fb.a(fb.java:34)
at com.ibm.db2.jcc.a.s.a(s.java:30)
at com.ibm.db2.jcc.a.h.Gb(h.java:325)
at com.ibm.db2.jcc.c.rc.R(rc.java:3028)
at com.ibm.db2.jcc.a.d.f(d.java:1070)
at com.ibm.db2.jcc.c.r.a(r.java:191)
at com.ibm.db2.jcc.c.rc.c(rc.java:302)
at com.ibm.db2.jcc.c.rc.next(rc.java:277)
at
org.apache.derby.impl.tools.dblook.DB_Table.createColumn(DB_Table.jav
a:143)
at
org.apache.derby.impl.tools.dblook.DB_Table.doTables(DB_Table.java:10
1)
at org.apache.derby.tools.dblook.go(dblook.java:529)
[EMAIL PROTECTED]:
-----------------
null
java.lang.NullPointerException
at
org.apache.derby.impl.drda.DRDAConnThread.writeFdocaVal(DRDAConnThread.java:6550)
at
org.apache.derby.impl.drda.DRDAConnThread.writeFDODTA(DRDAConnThread.java:5973)
at
org.apache.derby.impl.drda.DRDAConnThread.writeQRYDTA(DRDAConnThread.java:5796)
at
org.apache.derby.impl.drda.DRDAConnThread.processCommands(DRDAConnThread.java:595)
at
org.apache.derby.impl.drda.DRDAConnThread.run(DRDAConnThread.java:226)
agentThread[DRDAConnThread_2,5,main]
null
java.lang.NullPointerException
at
org.apache.derby.impl.drda.DRDAConnThread.writeFdocaVal(DRDAConnThread.java:6550)
at
org.apache.derby.impl.drda.DRDAConnThread.writeFDODTA(DRDAConnThread.java:5973)
at
org.apache.derby.impl.drda.DRDAConnThread.writeQRYDTA(DRDAConnThread.java:5796)
at
org.apache.derby.impl.drda.DRDAConnThread.processCommands(DRDAConnThread.java:595)
at
org.apache.derby.impl.drda.DRDAConnThread.run(DRDAConnThread.java:226)
------------------
I will start to consider how to fix the contradiction ....
Best regards.
/*
Tomohito Nakayama
[EMAIL PROTECTED]
[EMAIL PROTECTED]
Naka
http://www5.ocn.ne.jp/~tomohito/TopPage.html
*/
----- Original Message -----
From: "TomohitoNakayama" <[EMAIL PROTECTED]>
To: "Derby Development" <[email protected]>
Sent: Saturday, May 28, 2005 1:51 PM
Subject: about DERBY-318 (Re: DERBY-308 just be done and .... (Re: [jira]
Updated: (DERBY-308) Modify dblook to support "GENERATED BY DEFAULT AS
IDENTITY"))
Hello.
First of all, thank you for your kindness !
I understood the problem is that
there exists contradiction between rs.getString() and rs.wasNull()
for SYSCOLUMNS.COLUMNDEFAULT of column defined as GENERATED BY DEFAULT AS
IDENTITY.
I will start to see pheonemanas in my environment.
I think we need to consider way to solve DERBY-318 .
page 321 at next document says..
http://publibfp.boulder.ibm.com/epubs/pdf/cs51rm.pdf
for tables, describes default value of the column.
The toString() method on the object stored in the table returns the text
of the default value as specified in the
CREATE TABLE or ALTER TABLE statement.
for publication parameters, defines the default value of the parameter at
the source,
and the actual value of the parameter at the target
for stored prepared statements, defines a sample value for the parameter
used in a
CREATE STATEMENTor ALTER STATEMENT RECOMPILE statement
for optimization purposes
This is issue about table , so it is the matter how to interpret "text of
the default value as specified in the
CREATE TABLE or ALTER TABLE statement"
//BTW, what is publication parameters ...?
// I took somethink like table ....
Best regards.
/*
Tomohito Nakayama
[EMAIL PROTECTED]
[EMAIL PROTECTED]
Naka
http://www5.ocn.ne.jp/~tomohito/TopPage.html
*/
----- Original Message -----
From: "Army" <[EMAIL PROTECTED]>
To: "Derby Development" <[email protected]>
Sent: Saturday, May 28, 2005 10:03 AM
Subject: Re: DERBY-308 just be done and .... (Re: [jira] Updated:
(DERBY-308) Modify dblook to support "GENERATED BY DEFAULT AS IDENTITY")
TomohitoNakayama wrote:
If possible , I want to work for DERBY-318 before DERBY-308 ....
Tomohito,
I hope you don't mind, but when I filed DERBY-318, I wasn't sure whether
the problem was with the DERBY-167 patch or with the server. So, in
order to keep you from spending your time trying to track down a problem
that wasn't your fault, I started looking at this issue from the server
side of things--and I think I've found the problem.
To make a long story short, the NPE in the server happens because of the
"toString()" method defined in DefaultNodeImpl.
Why? Well, I try to explain it below. Excuse the formality of it all,
but I had to do it this way in order to keep it clear in my own head ;)
There are several pieces that make up the puzzle. Let me start by saying
what they are, and then I'll try to tie them together.
---------------
-- The pieces.
---------------
1) For a column that is GENERATED BY DEFAULT, the 'defaultText' variable
in the corresponding DefaultNodeImpl is null. Since
DefaultNodeImpl.toString() just returns defaultText, the result of
toString() on a DefaultNodeImpl that is GENERATED BY DEFAULT is null.
2) The underlying DataTypeDescriptor for all default columns is
"org.apache.derby.iapi.types.UserType". In that class, the "isNull()"
method is simply written to return "(value == null)", while the
"getString()" method is as follows:
public String getString()
{
if (! isNull())
{
return value.toString();
}
else
{
return null;
}
}
3) For a column that is GENERATED BY DEFAULT, the 'value' variable in
UserType is a non-null instance of DefaultNodeImpl.
---------------
-- The problem.
---------------
In Network Server, we take the result set from the query "SELECT
COLUMNDEFAULT FROM SYS.SYSCOLUMNS" and we do two things. First, we call
rs.getString(<columnNum>), and then we call rs.wasNull().
[ ** rs.getString() ** ]
* The call to rs.getString(...) on the "COLUMNDEFAULT" column ultimately
makes a call to UserType.getString() (Piece #2).
* That method in turn calls UserType.isNull().
* UserType.isNull() looks at 'value', which is a non-null instance of
DefaultNodeImpl(Piece #3 above), and since it's NOT null, it returns
"false" (Piece #2).
* UserType.getString() looks at the result from UserType.isNull(), which
is "false". It then calls "value.toString()" (Piece #2).
* Since 'value' is an instance of DefaultNodeImpl (Piece #3), this ends
up being a call to DefaultNodeImpl.toString().
* DefaultNodeImpl.toString() just returns 'defaultText', which is null
for columns that are GENERATED BY DEFAULT (Piece #1).
* UserType.getString() returns the null value that it got from
DefaultNodeImpl.toString().
* End result: the server call to "rs.getString()" returns null.
[ ** rs.wasNull() ** ]
* The server call to rs.wasNull() on the "COLUMNDEFAULT" column
ultimately makes a call to UserType.isNull().
* UserType.isNull() looks at 'value', which is a non-null instance of
DefaultNodeImpl(Piece #3 above), and since it's NOT null, it returns
"false" (Piece #2).
* End result: the server call to "rs.wasNull()" returns FALSE.
THEREFORE, the server calls rs.getString() and gets NULL back, but then
when it calls rs.wasNull(), it's told that the value it got back was NOT
null. So it tries to use the value (which IS null) and ends up with a
Null Pointer Exception.
---------------
Possible fix:
---------------
Just to verify that this is in the fact the problem, I changed the
"toString()" method in DefaultNodeImpl to the following:
public String toString()
{
if (isDefaultValueAutoinc())
return "GENERATED BY DEFAULT";
return defaultText;
}
What this means is that the server call to rs.getString() will now return
"GENERATED BY DEFAULT" instead of null. This in turn means that the
result of rs.wasNull() will be correct, and the result of the query
"SELECT COLUMNDEFAULT FROM SYS.SYSCOLUMNS" will be the string "GENERATED
BY DEFAULT".
I then ran the repro described in DERBY-318, and it ran correctly,
listing "GENERATED BY DEFAULT" as the default value for the column in
question.
That said, I think returning any non-null value in
DefaultNodeImpl.toString() will solve the problem The question then
becomes what value should we return? Is "GENERATED BY DEFAULT" an
acceptable result? To me, that seems like it should be okay--it says
that the default value isn't known, but that it's generated at insertion
time, if needed. But that's just me--it's quite possible other people
out there have a different opinion...
---------------
Conclusion:
---------------
1) This is NOT a Network Server problem (which is what I wanted to find
out, and that's why I started looking at it).
2) This problem can be fixed with two lines :) But I leave it up to the
others on this list to decide if this is the _best_ fix, and to decide on
what the non-null string value should be...
I hope that helps, and I hope you don't feel cheated because I took the
time to look into this. As I said, I wanted to make sure you weren't
chasing a problem that had its origins in Network Server...
Army
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