Re: Explain [Analyze] produces parallel scan for select Into table statements.
| От | Mithun Cy |
|---|---|
| Тема | Re: Explain [Analyze] produces parallel scan for select Into table statements. |
| Дата | |
| Msg-id | CAD__OuiFZWwohrfceu6SEdZ3Y4M7UbLFsT_KhFLJc5DARDNVnQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Explain [Analyze] produces parallel scan for select Into table statements. (Amit Kapila <amit.kapila16@gmail.com>) |
| Ответы |
Re: Explain [Analyze] produces parallel scan for select
Into table statements.
|
| Список | pgsql-hackers |
On Sat, Mar 12, 2016 at 12:28 PM, Amit Kapila <amit.kapila16@gmail.com> wrote
>I don't see how this test will fail with force_parallel_mode=regress and max_parallel_degree > 0 even without the patch proposed to fix the issue in >hand. In short, I don't think this test would have caught the issue, so I don't see much advantage in adding such a test. Even if we want to add such a >test case, I think as proposed this will substantially increase the timing for "Select Into" test which might not be an acceptable test case addition >especially for testing one corner case.
>I don't see how this test will fail with force_parallel_mode=regress and max_parallel_degree > 0 even without the patch proposed to fix the issue in >hand. In short, I don't think this test would have caught the issue, so I don't see much advantage in adding such a test. Even if we want to add such a >test case, I think as proposed this will substantially increase the timing for "Select Into" test which might not be an acceptable test case addition >especially for testing one corner case.
Without above patch the make installcheck fails for select_into.sql with below diff
when
force_parallel_mode = on
max_parallel_degree = 3
when
force_parallel_mode = on
max_parallel_degree = 3
diff results/select_into.out expected/select_into.out
104,110c104,107
< QUERY PLAN
< ------------------------
< Gather
< Number of Workers: 1
< Single Copy: true
< -> Seq Scan on mt1
< (4 rows)
---
> QUERY PLAN
> -----------------
> Seq Scan on mt1
> (1 row)
Again with postgresql.conf non default settings.
force_parallel_mode = on
max_parallel_degree = 3
parallel_tuple_cost = 0
[mithun@localhost regress]$ diff results/select_into.out expected/select_into.out
104,109c104,107
< QUERY PLAN
< --------------------------------
< Gather
< Number of Workers: 3
< -> Parallel Seq Scan on mt1
< (3 rows)
---
> QUERY PLAN
> -----------------
> Seq Scan on mt1
> (1 row)
To reduce the time of execution I can set the generate_series parameter to 500, which is fast in my machine and also fails with above diff but this time only one worker is assigned as per plan.
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