Обсуждение: ODBC SQLSetPos Delete problem
Hi,
some weeks I have asked about a possible bug in pSQLODBC driver.
Now I have downloaded the driver source to get a debug version
of the driver.
The problem occurs at the following code line (973) in statement.c:
Code area:
mylog("type = %d and valuepointer here is %p\n", type, value);
if (self->manual_result) {
value = QR_get_value_manual(res, self->currTuple, lf);
mylog("manual_result\n");
} else if (SC_is_fetchcursor(self))
value = QR_get_value_backend(res, lf);
else {
int curt = GIdx2ResultIdx(self->currTuple, self, res);
value = QR_get_value_backend_row(res, curt, lf);
}
mylog("value = '%s'\n", (value == NULL) ? "<NULL>" : value); // CRASH
The pointer value is 0xdddddddd
As for the log messages now I see , that I have forgotten a reload
after the deletion and the driver may not save this state to avoid
such a crash.
I do not know where the pointer comes from, but see this as a hint:
Could this be used for buffer overruns ?
Hope to hear from you :-)
Lothar
---- My home: www.lollisoft.de -----------------------------
Lothar Behrens | Independent: lothar.behrens@gmx.de
Rosmarinstr 3 | My public project:
40235 Düsseldorf | http://sourceforge.net/projects/lbdmf
| -> Need comments, please visit :-)
Hi, it seems that I did not get any help. Now I also like to say, that If I test a Sybase Power++ Developer application with simple db form, I get a crash in the Postgres ODBC driver. The form is created with the wizard and uses cursors. The driver seems to delete the record, but moving to next/prev record fails. Who can help me ? Do you like to have the source ? You can dounload it. I can try to debug the ODBC library, but I do not understand the full source, so I need a little help. Thanks Lothar ---- My home: www.lollisoft.de ----------------------------- Lothar Behrens | Independent: lothar.behrens@gmx.de Rosmarinstr 3 | My public project: 40235 Düsseldorf | http://sourceforge.net/projects/lbdmf | -> Need comments, please visit :-)
-----Original Message----- From: pgsql-odbc-owner@postgresql.org on behalf of Lothar Behrens Sent: Tue 9/14/2004 6:07 PM To: pgsql-odbc@postgresql.org Subject: Re: [ODBC] ODBC SQLSetPos Delete problem > I can try to debug the ODBC library, but I do not understand the full > source, so I need a little help. Unfortunately that is the problem - there isn't anyone left on the project who really understands the source code, and infact the cursor code is very experimental and was one of the last features worked on by the last guy that did know whathe was doing :-( I have (very) limited time right now, but if you let me have some more details of the problem I'll see if I can help at all(no promises though). Regards, Dave
Lothar Behrens wrote: > I can try to debug the ODBC library, but I do not understand the full > source, so I need a little help. If there is a crash, you should get a stack backtrace from the core file and examine the local state to find out what caused it to crash. -- Peter Eisentraut http://developer.postgresql.org/~petere/
> Lothar Behrens wrote: > > I can try to debug the ODBC library, but I do not understand the full > > source, so I need a little help. > > If there is a crash, you should get a stack backtrace from the core file > and examine the local state to find out what caused it to crash. In my first posting for this thread, I gave the exact position in the sourcecode of the driver. As other postings say, the pointer 0xdddddddd is a deleted memory area. The pointer in use is a local variable in the function mentioned. The crash surprisingly happens while debuging is switched on in ODBC configuration. If I have no debug informations, it crashes later. I would have a deeper look at the driver code to find out more and understand the code. PS. I mainly develop on windows 2000 and using Open Watcom. Is the stack backtrace based on linux or on windows using MSVC ? Thanks > > -- > Peter Eisentraut > http://developer.postgresql.org/~petere/ > > > ---------------------------(end of broadcast)--------------------------- > TIP 9: the planner will ignore your desire to choose an index scan if your > joining column's datatypes do not match > ---- My home: www.lollisoft.de ----------------------------- Lothar Behrens | Independent: lothar.behrens@gmx.de Rosmarinstr 3 | My public project: 40235 Düsseldorf | http://sourceforge.net/projects/lbdmf | -> Need comments, please visit :-)
I think you and we need details. You say the form uses cursors. This suggest to me that maybe you are trying to update a connected recordset, versus using a disconnected recordset. I hope this is not talking down to anyone, but a disconnected recordset is one where you get the records, then the server can forget about you. A connected recordset is keeping the connection alive until you are done with your recordset, that is close your form. I have always avoided connected recordsets for client-server applications. I use disconnected recordset when I want to read data. I use INSERT, UPDATE, AND DELETE statements (against primary keys and indexes) when I wish to modify data. My understanding is not perfectly clear on this, but I think that the PostgreSQL driver does not do connected recordsets. But the ODBC driver may fake it under certain conditions. It is suggested that there be OIDS on the server table. It is suggested that the server table have a primary key. It is suggested that row versioning be turned on in the ODBC driver. There are conditions where table row uniqueness is forced by the adding of a timestamp field that defaults to Now(). So while it may appear to a user that a database table is attached,... the behind the scenes is a sequence of row fetches, and discrete insert, update, delete statements that need to find the records to work on. To this end, and back to those details Does your table have OIDS? Does your table have a primary key? Have you turned on all the logging you can, client and server to see what is going on at lower levels? Are there options in your application wizard regarding connections? (I doubt we can help you with) Could you build the application in a different way to separate data reading transaction from data updating transactions? I hope that 1. I am not completely off the mark 2. that I have given you something to think about that you did not already have. Good Luck. Lothar Behrens wrote: >Hi, > >it seems that I did not get any help. Now I also like to say, that >If I test a Sybase Power++ Developer application with simple db form, >I get a crash in the Postgres ODBC driver. > >The form is created with the wizard and uses cursors. > >The driver seems to delete the record, but moving to next/prev record >fails. > >Who can help me ? > >Do you like to have the source ? >You can dounload it. > >I can try to debug the ODBC library, but I do not understand the full >source, so I need a little help. > >Thanks > >Lothar >---- My home: www.lollisoft.de ----------------------------- >Lothar Behrens | Independent: lothar.behrens@gmx.de >Rosmarinstr 3 | My public project: >40235 Düsseldorf | http://sourceforge.net/projects/lbdmf > | -> Need comments, please visit :-) > > >---------------------------(end of broadcast)--------------------------- >TIP 8: explain analyze is your friend > >
Вложения
I forgot to mention what may or may not be obvious. A connected recordset is more technically known as a server side cursor. A disconnect recordset is more correctly known as a client side cursor. The client side cursor brings all the records back to the client and establishes a pointer to them. The server side cursor is like an open pointer to a set of records on the server. So not all cursors are equal. Some applications use server side cursors -- probably poorly supported by PostgreSQL. Some applications use client-side cursors with updates not done in against a remote pointer,... but done on with behind the scene SQL statement against rows. So checking for row versioning on the driver set-up can be important. Perhaps you could remind us -- what platform is the application on? What driver are you using to make the connection? What is the server platform? Greg Campbell wrote: > I think you and we need details. > You say the form uses cursors. This suggest to me that maybe you are > trying to update a connected recordset, versus using a disconnected > recordset. I hope this is not talking down to anyone, but a > disconnected recordset is one where you get the records, then the > server can forget about you. A connected recordset is keeping the > connection alive until you are done with your recordset, that is close > your form. > > I have always avoided connected recordsets for client-server > applications. I use disconnected recordset when I want to read data. I > use INSERT, UPDATE, AND DELETE statements (against primary keys and > indexes) when I wish to modify data. > > My understanding is not perfectly clear on this, but I think that the > PostgreSQL driver does not do connected recordsets. But the ODBC > driver may fake it under certain conditions. > It is suggested that there be OIDS on the server table. > It is suggested that the server table have a primary key. > It is suggested that row versioning be turned on in the ODBC driver. > There are conditions where table row uniqueness is forced by the > adding of a timestamp field that defaults to Now(). > So while it may appear to a user that a database table is attached,... > the behind the scenes is a sequence of row fetches, and discrete > insert, update, delete statements that need to find the records to > work on. > > > To this end, and back to those details > > Does your table have OIDS? > Does your table have a primary key? > Have you turned on all the logging you can, client and server to see > what is going on at lower levels? > Are there options in your application wizard regarding connections? (I > doubt we can help you with) > Could you build the application in a different way to separate data > reading transaction from data updating transactions? > > I hope that > 1. I am not completely off the mark > 2. that I have given you something to think about that you did not > already have. > > Good Luck. > > Lothar Behrens wrote: > >> Hi, >> >> it seems that I did not get any help. Now I also like to say, that >> If I test a Sybase Power++ Developer application with simple db form, >> I get a crash in the Postgres ODBC driver. >> >> The form is created with the wizard and uses cursors. >> >> The driver seems to delete the record, but moving to next/prev record >> fails. >> >> Who can help me ? >> >> Do you like to have the source ? >> You can dounload it. >> >> I can try to debug the ODBC library, but I do not understand the full >> source, so I need a little help. >> >> Thanks >> >> Lothar >> ---- My home: www.lollisoft.de ----------------------------- >> Lothar Behrens | Independent: lothar.behrens@gmx.de >> Rosmarinstr 3 | My public project: >> 40235 Düsseldorf | http://sourceforge.net/projects/lbdmf >> | -> Need comments, please visit :-) >> >> >> ---------------------------(end of broadcast)--------------------------- >> TIP 8: explain analyze is your friend >> >> >---------------------------(end of broadcast)--------------------------- >TIP 3: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly > >
Вложения
Lothar, As a workaround, what about writing your code in plpgsql, and call the function from your Power++ Developer application?With this technique, your app will be faster, and you'll be protected from possible bugs in the driver. (AnywayI cannot say if what you experiment is a bug...) I'm working like this with a MS Access front-end, and it works really fine. Code is centralized, so when you need updatingit, it's easier... Hope this helps, Philippe -----Message d'origine----- De : pgsql-odbc-owner@postgresql.org [mailto:pgsql-odbc-owner@postgresql.org] De la part de Lothar Behrens Envoyé : mardi, 14. septembre 2004 19:07 À : pgsql-odbc@postgresql.org Objet : Re: [ODBC] ODBC SQLSetPos Delete problem Hi, it seems that I did not get any help. Now I also like to say, that If I test a Sybase Power++ Developer application withsimple db form, I get a crash in the Postgres ODBC driver. The form is created with the wizard and uses cursors. The driver seems to delete the record, but moving to next/prev record fails. Who can help me ? Do you like to have the source ? You can dounload it. I can try to debug the ODBC library, but I do not understand the full source, so I need a little help. Thanks Lothar ---- My home: www.lollisoft.de ----------------------------- Lothar Behrens | Independent: lothar.behrens@gmx.de Rosmarinstr 3 | My public project: 40235 Düsseldorf | http://sourceforge.net/projects/lbdmf | -> Need comments, please visit :-) ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
Hi, I've used various versions of the PostgreSQL odbc driver on Windows and Unix. I found that versions 7.2.1 to 7.2.2 will not crash but will give an error when subsequently fetching a row after having deleted a row even though the delete works OK. With versions 7.2.3 to 7.3.3 the program will crash but this is not consistent depending on the table involved and what platform the driver is on. I think you're best bet is to either use a different version of the driver although I don't know if this can work in your app, or better yet, do what Philippe has suggested. Good luck! -- Janet > -----Original Message----- > From: Philippe Lang [mailto:philippe.lang@attiksystem.ch] > Sent: Wednesday, September 15, 2004 12:05 AM > To: pgsql-odbc@postgresql.org > Cc: Lothar Behrens > Subject: Re: [ODBC] ODBC SQLSetPos Delete problem > > > Lothar, > > As a workaround, what about writing your code in plpgsql, and > call the function from your Power++ Developer application? > With this technique, your app will be faster, and you'll be > protected from possible bugs in the driver. (Anyway I cannot > say if what you experiment is a bug...) > > I'm working like this with a MS Access front-end, and it > works really fine. Code is centralized, so when you need > updating it, it's easier... > > Hope this helps, > > Philippe > > -----Message d'origine----- > De : pgsql-odbc-owner@postgresql.org > [mailto:pgsql-odbc-owner@postgresql.org] De la part > de Lothar > Behrens Envoyé : mardi, 14. septembre 2004 19:07 À : > pgsql-odbc@postgresql.org Objet : Re: [ODBC] ODBC SQLSetPos > Delete problem > > Hi, > > it seems that I did not get any help. Now I also like to say, > that If I test a Sybase Power++ Developer application with > simple db form, I get a crash in the Postgres ODBC driver. > > The form is created with the wizard and uses cursors. > > The driver seems to delete the record, but moving to > next/prev record fails. > > Who can help me ? > > Do you like to have the source ? > You can dounload it. > > I can try to debug the ODBC library, but I do not understand > the full source, so I need a little help. > > Thanks > > Lothar > ---- My home: www.lollisoft.de ----------------------------- > Lothar Behrens | Independent: lothar.behrens@gmx.de > Rosmarinstr 3 | My public project: > 40235 Düsseldorf | http://sourceforge.net/projects/lbdmf > | -> Need comments, please visit :-) > > > ---------------------------(end of > broadcast)--------------------------- > TIP 8: explain analyze is your friend > > > > ---------------------------(end of > broadcast)--------------------------- > TIP 3: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so > that your > message can get through to the mailing list cleanly >
> Hi, > I've used various versions of the PostgreSQL odbc driver on Windows and > Unix. I found that versions 7.2.1 to 7.2.2 will not crash but will give an > error when subsequently fetching a row after having deleted a row even > though the delete works OK. With versions 7.2.3 to 7.3.3 the program will > crash but this is not consistent depending on the table involved and what > platform the driver is on. > Thanks, I will try this version. I also have a new idea: As for a financial system, a customer with invoices must not be allowed to be deleted. In germany this is a must law. On the other hand, if I like to enable a deletion, I would do this with a delete flag and explicid cleanup code at the connection or at disconnetion from the database. Updating of rows works fine in my code and adding too, so wy not updating a delete flag internally in my ODBC wrapper ? Thanks Lothar > I think you're best bet is to either use a different version of the driver > although I don't know if this can work in your app, or better yet, do what > Philippe has suggested. > > Good luck! > > -- Janet > > > > -----Original Message----- > > From: Philippe Lang [mailto:philippe.lang@attiksystem.ch] > > Sent: Wednesday, September 15, 2004 12:05 AM > > To: pgsql-odbc@postgresql.org > > Cc: Lothar Behrens > > Subject: Re: [ODBC] ODBC SQLSetPos Delete problem > > > > > > Lothar, > > > > As a workaround, what about writing your code in plpgsql, and > > call the function from your Power++ Developer application? > > With this technique, your app will be faster, and you'll be > > protected from possible bugs in the driver. (Anyway I cannot > > say if what you experiment is a bug...) > > > > I'm working like this with a MS Access front-end, and it > > works really fine. Code is centralized, so when you need > > updating it, it's easier... > > > > Hope this helps, > > > > Philippe > > > > -----Message d'origine----- > > De : pgsql-odbc-owner@postgresql.org > > [mailto:pgsql-odbc-owner@postgresql.org] De la part > de Lothar > > Behrens Envoyé : mardi, 14. septembre 2004 19:07 À : > > pgsql-odbc@postgresql.org Objet : Re: [ODBC] ODBC SQLSetPos > > Delete problem > > > > Hi, > > > > it seems that I did not get any help. Now I also like to say, > > that If I test a Sybase Power++ Developer application with > > simple db form, I get a crash in the Postgres ODBC driver. > > > > The form is created with the wizard and uses cursors. > > > > The driver seems to delete the record, but moving to > > next/prev record fails. > > > > Who can help me ? > > > > Do you like to have the source ? > > You can dounload it. > > > > I can try to debug the ODBC library, but I do not understand > > the full source, so I need a little help. > > > > Thanks > > > > Lothar > > ---- My home: www.lollisoft.de ----------------------------- > > Lothar Behrens | Independent: lothar.behrens@gmx.de > > Rosmarinstr 3 | My public project: > > 40235 Düsseldorf | http://sourceforge.net/projects/lbdmf > > | -> Need comments, please visit :-) > > > > > > ---------------------------(end of > > broadcast)--------------------------- > > TIP 8: explain analyze is your friend > > > > > > > > ---------------------------(end of > > broadcast)--------------------------- > > TIP 3: if posting/reading through Usenet, please send an appropriate > > subscribe-nomail command to majordomo@postgresql.org so > > that your > > message can get through to the mailing list cleanly > > > > ---------------------------(end of broadcast)--------------------------- > TIP 3: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly > ---- My home: www.lollisoft.de ----------------------------- Lothar Behrens | Independent: lothar.behrens@gmx.de Rosmarinstr 3 | My public project: 40235 Düsseldorf | http://sourceforge.net/projects/lbdmf | -> Need comments, please visit :-)
> -----Original Message----- > From: pgsql-odbc-owner@postgresql.org > [mailto:pgsql-odbc-owner@postgresql.org] On Behalf Of Janet Borschowa > Sent: 15 September 2004 17:14 > To: pgsql-odbc@postgresql.org > Cc: Lothar Behrens > Subject: Re: [ODBC] ODBC SQLSetPos Delete problem > > Hi, > I've used various versions of the PostgreSQL odbc driver on > Windows and Unix. I found that versions 7.2.1 to 7.2.2 will > not crash but will give an error when subsequently fetching a > row after having deleted a row even though the delete works > OK. With versions 7.2.3 to 7.3.3 the program will crash but > this is not consistent depending on the table involved and > what platform the driver is on. > > I think you're best bet is to either use a different version > of the driver although I don't know if this can work in your > app, or better yet, do what Philippe has suggested. Out of interest, does it still crash if you turn off the updateable cursors option? Regards, Dave.
Hi Dave, Its been awhile since I did this testing (about a year) but the only crashes I remember seeing, and the only ones in my notes, were involving writable cursors to update/delete rows. When my writable cursor tests were disabled I didn't see any crashes. Since writable cursors had to be supported I never did much, if any, testing without the UpdatableCursors option. Since then, I've been developing with libpq so I don't think I'll get the time to go back and try this out. :-( -- Janet > -----Original Message----- > From: Dave Page [mailto:dpage@vale-housing.co.uk] > Sent: Wednesday, September 15, 2004 12:53 PM > To: Janet Borschowa; pgsql-odbc@postgresql.org > Cc: Lothar Behrens > Subject: RE: [ODBC] ODBC SQLSetPos Delete problem > > > > > > -----Original Message----- > > From: pgsql-odbc-owner@postgresql.org > > [mailto:pgsql-odbc-owner@postgresql.org] On Behalf Of Janet > Borschowa > > Sent: 15 September 2004 17:14 > > To: pgsql-odbc@postgresql.org > > Cc: Lothar Behrens > > Subject: Re: [ODBC] ODBC SQLSetPos Delete problem > > > > Hi, > > I've used various versions of the PostgreSQL odbc driver on > > Windows and Unix. I found that versions 7.2.1 to 7.2.2 will > > not crash but will give an error when subsequently fetching a > > row after having deleted a row even though the delete works > > OK. With versions 7.2.3 to 7.3.3 the program will crash but > > this is not consistent depending on the table involved and > > what platform the driver is on. > > > > I think you're best bet is to either use a different version > > of the driver although I don't know if this can work in your > > app, or better yet, do what Philippe has suggested. > > Out of interest, does it still crash if you turn off the > updateable cursors option? > > Regards, Dave. >
> > Out of interest, does it still crash if you turn off the updateable > cursors option? I must use updateable cursors, because my classes do not automatically build update statements. It would be creat, if one could help me with such a variant. OT: Wy you all mail me a copy directly ? I get it from the list. :-) Lothar > > Regards, Dave. > > ---------------------------(end of broadcast)--------------------------- > TIP 6: Have you searched our list archives? > > http://archives.postgresql.org > ---- My home: www.lollisoft.de ----------------------------- Lothar Behrens | Independent: lothar.behrens@gmx.de Rosmarinstr 3 | My public project: 40235 Düsseldorf | http://sourceforge.net/projects/lbdmf | -> Need comments, please visit :-)
Hi, I have another question: As seen, there is a libpqxx library. This is a C++ library following the STL and it also supports 'cursors' in another way. Would it be a good idea to write a wrapper around it to support my class interfaces ? Lothar ---- My home: www.lollisoft.de ----------------------------- Lothar Behrens | Independent: lothar.behrens@gmx.de Rosmarinstr 3 | My public project: 40235 Düsseldorf | http://sourceforge.net/projects/lbdmf | -> Need comments, please visit :-)
Hi Lothar, I don't have any experience using the libpqxx API but I have used the libpq API and I have found that writable cursors can be implemented in it without too much trouble. The PostgreSQL server does not support writable cursors (see the SQL statement 'declare') so you will need to implement those yourself. I would choose to use libpq rather than some other API that is not distributed with the server. The reason is that it is more likely to remain supported/stable than some other API (such as psqlodbc). If you haven't seen it already, there is an object-oriented interface based on the libpq API, SourcePro(TM) DB PostgreSQL Access Module, which supports writable cursors (and most everything else). It is available from Rogue Wave Software at: http://www.roguewave.com/products/sourcepro/db/ ======================== Janet Borschowa Software Engineer, Database Products Rogue Wave Software, a QUOVADX(tm) Division http://www.roguewave.com > -----Original Message----- > From: Lothar Behrens [mailto:lothar.behrens@lollisoft.de] > Sent: Thursday, September 16, 2004 11:03 AM > To: pgsql-odbc@postgresql.org > Subject: Re: [ODBC] ODBC SQLSetPos Delete problem > > > Hi, > > I have another question: > > As seen, there is a libpqxx library. This is a C++ library > following the STL and it also supports 'cursors' in another way. > > Would it be a good idea to write a wrapper around it to > support my class interfaces ? > > Lothar > ---- My home: www.lollisoft.de ----------------------------- > Lothar Behrens | Independent: lothar.behrens@gmx.de > Rosmarinstr 3 | My public project: > 40235 Düsseldorf | http://sourceforge.net/projects/lbdmf > | -> Need comments, please visit :-) > > > ---------------------------(end of > broadcast)--------------------------- > TIP 6: Have you searched our list archives? > http://archives.postgresql.org