Re: Columns correlation and adaptive query optimization
| От | Zhihong Yu |
|---|---|
| Тема | Re: Columns correlation and adaptive query optimization |
| Дата | |
| Msg-id | CALNJ-vRh-53giL4cfz4cCEHnqMKdevOws7trdwHJigS1918q-A@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Columns correlation and adaptive query optimization (Konstantin Knizhnik <k.knizhnik@postgrespro.ru>) |
| Ответы |
Re: Columns correlation and adaptive query optimization
|
| Список | pgsql-hackers |
Hi,
In AddMultiColumnStatisticsForQual(),
+ /* Loop until we considered all vars */
+ while (vars != NULL)
+ while (vars != NULL)
...
+ /* Contruct list of unique vars */
+ foreach (cell, vars)
+ foreach (cell, vars)
What if some cell / node, gets into the else block:
+ else
+ {
+ continue;
+ {
+ continue;
and being left in vars. Is there a chance for infinite loop ?
It seems there should be a bool variable indicating whether any cell gets to the following:
+ vars = foreach_delete_current(vars, cell);
If no cell gets removed in the current iteration, the outer while loop should exit.
Cheers
On Fri, Mar 19, 2021 at 9:58 AM Konstantin Knizhnik <k.knizhnik@postgrespro.ru> wrote:
On 19.03.2021 12:17, Yugo NAGATA wrote:
> On Wed, 10 Mar 2021 03:00:25 +0100
> Tomas Vondra <tomas.vondra@enterprisedb.com> wrote:
>
>> What is being proposed here - an extension suggesting which statistics
>> to create (and possibly creating them automatically) is certainly
>> useful, but I'm not sure I'd call it "adaptive query optimization". I
>> think "adaptive" means the extension directly modifies the estimates
>> based on past executions. So I propose calling it maybe "statistics
>> advisor" or something like that.
> I am also agree with the idea to implement this feature as a new
> extension for statistics advisor.
>
>> BTW Why is "qual" in
>>
>> static void
>> AddMultiColumnStatisticsForQual(void* qual, ExplainState *es)
>>
>> declared as "void *"? Shouldn't that be "List *"?
> When I tested this extension using TPC-H queries, it raised segmentation
> fault in this function. I think the cause would be around this argument.
>
> Regards,
> Yugo Nagata
>
Attached please find new version of the patch with
AddMultiColumnStatisticsForQual parameter type fix and one more fix
related with handling synthetic attributes.
I can not reproduce the crash on TPC-H queries, so if the problem
persists, can you please send me stack trace and may be some other
information helping to understand the reason of SIGSEGV?
Thanks in advance,
Konstantin
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