Re: Problems with MemoryContextSwitchTo ()

pá 18. 9. 2020 v 6:35 odesílatel Yessica Brinkmann <
brinkmann(dot)yessica(at)gmail(dot)com> napsal:

> I already discovered the problem, it was only a counter initialization
> issue, it had nothing to do with memory contexts, that part was fine. Thank
> God I could already understand the problem and solve it.
> Anyway thank you very much.
> Best regards,
> Yessica Brinkmann
>

Great! These problems forward us :). It is very common so the problem is
somewhere else than we are finding.

Pavel

> El jue., 17 sept. 2020 a las 22:26, Yessica Brinkmann (<
> brinkmann(dot)yessica(at)gmail(dot)com>) escribió:
>
>> Thank you very much for the answers, and for the advice given. I will
>> try to put them into practice.
>> Best regards,
>> Yessica Brinkmann
>>
>>
>> El jue., 17 sept. 2020 a las 6:46, Yessica Brinkmann (<
>> brinkmann(dot)yessica(at)gmail(dot)com>) escribió:
>>
>>>
>>>
>>> Good Morning. Thank you so much for the answers. Now I have to go to
>>> work, but when I come back I will be looking at the answers in detail, and
>>> I will answer. Unfortunately I have to work and study as well, so right now
>>> I can't see the answers in detail.
>>> Best regards,
>>> Yessica Brinkmann.
>>>
>>>
>>> -------- Mensaje original --------
>>> Asunto: Re: Problems with MemoryContextSwitchTo ()
>>> De: Pavel Stehule
>>> Para: Yessica Brinkmann
>>> CC: pgsql-general
>>>
>>>
>>>
>>>
>>> čt 17. 9. 2020 v 6:09 odesílatel Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
>>> napsal:
>>>
>>>>
>>>>
>>>> čt 17. 9. 2020 v 3:16 odesílatel Yessica Brinkmann <
>>>> brinkmann(dot)yessica(at)gmail(dot)com> napsal:
>>>>
>>>>> Good night,
>>>>> Thank you very much for the answer.
>>>>> Excuse me please just answered, I was at my job.
>>>>> And yes, I get the results of the list with SPI_exec.
>>>>> And I am also using SPI_finish (). But I save the results of the
>>>>> previous query in the array idxcd-> varattnnames.
>>>>> And in the second foreach it should print me the values that I got in
>>>>> the query, since I print the values of idxcd-> varattnnames, but it is
>>>>> printing null.
>>>>> And I think the memory context switch is fine too, so I really don't
>>>>> know why it prints null to me.
>>>>> I will greatly appreciate a help please. I can't really understand
>>>>> why it prints null in the second foreach, even though I already tried
>>>>> various changes.
>>>>>
>>>>
>>>> do you use Postgres with active assertions ?
>>>>
>>>> postgres=# show debug_assertions ;
>>>> ┌──────────────────┐
>>>> │ debug_assertions │
>>>> ╞══════════════════╡
>>>> │ on │
>>>> └──────────────────┘
>>>> (1 row)
>>>>
>>>> maybe you somewhere allocate less memory then it is necessary and some
>>>> memset rewrites memory with your data. When you have a problem with memory,
>>>> then you should to very carefully check a) if memory is allocated in good
>>>> context, b) if memory was allocated enough (sometimes I just allocated x +
>>>> 100000 for testing).
>>>>
>>>> Can you write a reproducer ? code that I can check at my home. Postgres
>>>> is pretty complex system, and it is hard to fix some issue without access
>>>> to code
>>>>
>>>>
>>> This is some messy in your code
>>>
>>> MemoryContext oldContext = MemoryContextSwitchTo( outerContext );
>>> MemoryContextSwitchTo( oldContext );
>>>
>>> Unfortunately, your code is not well structured - it is hard to read it.
>>> One hint - if you find an issue - try to reduce lines of your code which is
>>> possible until you reproduce this issue or until you understand this issue.
>>>
>>> The sequence of statements is a little bit obscure :)
>>>
>>> initStringInfo( &query );
>>>
>>> */
>>> if( cols.len > 0 )
>>> {
>>> initStringInfo(&cols);
>>> } /*IF col.len>0*/
>>>
>>> Instead
>>>
>>> foreach( cell, candidates ) /* foreach cell in candidates */
>>> {
>>>
>>> int i;
>>>
>>>
>>>
>>> /*elog (INFO, "Ingresando a foreach");*/
>>> idxcd = (IndexCandidate*)lfirst( cell );
>>>
>>> if (idxcd == NULL) {
>>> elog( INFO, "idxcd IS NULL" );
>>> continue; /* Or is that fatal enough to break instead? */
>>> }
>>>
>>>
>>> you can write
>>>
>>> idxcd = (IndexCandidate *) linitial(candidates);
>>>
>>> The problem in your example is fact so it is a mix of copy/paste
>>> fragments. I wrote similar code, and almost everyone I know (when I
>>> started). But it is not possible to fix this code - start from scratch. The
>>> code must be readable (every time). And when I write code inside some
>>> complex environment (like Postgres is), I write code in very small
>>> fragments, in very small steps, and every time I try to compile, restart
>>> and check the result. Then I know what line, or what statement is the
>>> problem.
>>>
>>> Regards
>>>
>>> Pavel
>>>
>>>
>>>
>>>
>>>
>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Best regards,
>>>>> Yessica Brinkmann
>>>>>
>>>>> El mié., 16 sept. 2020 a las 9:16, Pavel Stehule (<
>>>>> pavel(dot)stehule(at)gmail(dot)com>) escribió:
>>>>>
>>>>>>
>>>>>>
>>>>>> st 16. 9. 2020 v 15:09 odesílatel Yessica Brinkmann <
>>>>>> brinkmann(dot)yessica(at)gmail(dot)com> napsal:
>>>>>>
>>>>>>> Well, the fact is that I have a function called get_columnnames,
>>>>>>> which in the second foreach, is printing the values of idxcd-> varattnnames
>>>>>>> [i] the null value. This is the error.
>>>>>>
>>>>>>
>>>>>> How you get this list? It is result of SPI_exec*** ?
>>>>>>
>>>>>> There is SPI_finish(), that cleaning a memory used by SPI interface,
>>>>>> and theoretically it can clean result of previous query.
>>>>>>
>>>>>> Regards
>>>>>>
>>>>>> Pavel
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> -------- Mensaje original --------
>>>>>>> Asunto: Re: Problems with MemoryContextSwitchTo ()
>>>>>>> De: Pavel Stehule
>>>>>>> Para: Yessica Brinkmann
>>>>>>> CC: pgsql-general
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> st 16. 9. 2020 v 13:32 odesílatel Yessica Brinkmann <
>>>>>>> brinkmann(dot)yessica(at)gmail(dot)com> napsal:
>>>>>>>
>>>>>>>> Good Morning.
>>>>>>>> I will greatly appreciate a help please on this subject. I
>>>>>>>> actually did several tests already and tried a lot to fix it myself. But
>>>>>>>> I am not able to. And I really need to know this in order to
>>>>>>>> finish my university thesis. If someone can help me please.
>>>>>>>> Best regards,
>>>>>>>> Yessica Brinkmann
>>>>>>>>
>>>>>>>
>>>>>>> please, can you attach your code, and can you show the error
>>>>>>> message?
>>>>>>>
>>>>>>> It is hard to say what is the problem from your mail?
>>>>>>>
>>>>>>> Regards
>>>>>>>
>>>>>>> Pavel
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>> El mié., 16 sept. 2020 a las 0:42, Yessica Brinkmann (<
>>>>>>>> brinkmann(dot)yessica(at)gmail(dot)com>) escribió:
>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Hello.
>>>>>>>>> I think several of you will already remember me. I'm the one with
>>>>>>>>> the IndexAdviser topic. Only that I changed my email address.
>>>>>>>>> As you may recall, I am doing my thesis on the subject of
>>>>>>>>> IndexAdviser modifications.
>>>>>>>>> I really appreciate the help they have given me in various
>>>>>>>>> Postgresql groups.
>>>>>>>>> Well, I was really nearing the end of the programming part of the
>>>>>>>>> thesis, when I had a problem to be able to compile my program in a moment,
>>>>>>>>> and by accident some lines of source code were moved.
>>>>>>>>> And for this reason, I think I have problems again with the
>>>>>>>>> context switch issue, since at some point my context switch stopped working
>>>>>>>>> for me, I think because of the issue that some lines of source code were
>>>>>>>>> moved.
>>>>>>>>> Well, the fact is that I have a function called get_columnnames,
>>>>>>>>> which in the second foreach, is printing the values of idxcd-> varattnnames
>>>>>>>>> [i] the null value.
>>>>>>>>> This second foreach, I only do it to test if the data is really
>>>>>>>>> saved well and if I can recover it properly.
>>>>>>>>> And since the data is not retrieved properly, or is not saved
>>>>>>>>> properly, in the following functions of my program, the value of idxcd->
>>>>>>>>> varattnnames [i] continues to appear as null.
>>>>>>>>> I will appreciate a lot please help, if you can tell me please why
>>>>>>>>> the function prints null in the values of idxcd-> varattnnames [i], in the
>>>>>>>>> second foreach, if it is due to an error in the context switch, or why it
>>>>>>>>> could be .
>>>>>>>>>
>>>>>>>>> I send my function as an attachment.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Best regards,
>>>>>>>>> Yessica Brinkmann.
>>>>>>>>>
>>>>>>>>