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* Copy command hangs in poll() function
@ 2018-10-04 05:35 Akshay Joshi <[email protected]>
2018-10-04 10:26 ` Re: Copy command hangs in poll() function Daniele Varrazzo <[email protected]>
0 siblings, 1 reply; 4+ messages in thread
From: Akshay Joshi @ 2018-10-04 05:35 UTC (permalink / raw)
To: psycopg
Hello
As per documentation http://initd.org/psycopg/docs/advanced.html Copy
commands are not supported in asynchronous mode, but this will be probably
implemented in a future release. In pgAdmin4 (open source) we have used
async connection to run the SQL query on PostgreSQL database and uses
poll() function to poll the results. When user runs any *COPY *command
application hangs at poll() function.
If copy command not supported then at least it should not hang the
application. poll() function should return the proper error message.
Can you please provide that fix until support for copy command won't come.
--
*Akshay Joshi*
*Sr. Software Architect *
*Phone: +91 20-3058-9517Mobile: +91 976-788-8246*
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Copy command hangs in poll() function
2018-10-04 05:35 Copy command hangs in poll() function Akshay Joshi <[email protected]>
@ 2018-10-04 10:26 ` Daniele Varrazzo <[email protected]>
2018-10-04 10:29 ` Re: Copy command hangs in poll() function Daniele Varrazzo <[email protected]>
2018-10-04 10:33 ` Re: Copy command hangs in poll() function Federico Di Gregorio <[email protected]>
0 siblings, 2 replies; 4+ messages in thread
From: Daniele Varrazzo @ 2018-10-04 10:26 UTC (permalink / raw)
To: [email protected]; +Cc: psycopg
On Thu, Oct 4, 2018 at 6:35 AM Akshay Joshi <[email protected]>
wrote:
> Hello
>
> As per documentation http://initd.org/psycopg/docs/advanced.html Copy
> commands are not supported in asynchronous mode, but this will be probably
> implemented in a future release. In pgAdmin4 (open source) we have used
> async connection to run the SQL query on PostgreSQL database and uses
> poll() function to poll the results. When user runs any *COPY *command
> application hangs at poll() function.
>
> If copy command not supported then at least it should not hang the
> application. poll() function should return the proper error message.
>
> Can you please provide that fix until support for copy command won't come.
>
Uhm, I see:
In [2]: cnn = psycopg2.connect("")
In [3]: cur = cnn.cursor()
In [4]: cur.execute("copy (select 1 as x) to stdout")
---------------------------------------------------------------------------
ProgrammingError Traceback (most recent call
last)
<ipython-input-4-62e3af3d121e> in <module>()
----> 1 cur.execute("copy (select 1 as x) to stdout")
ProgrammingError: can't execute COPY TO: use the copy_to() method
instead
but:
In [6]: cnn = psycopg2.connect("", async=True)
In [7]: cnn.poll()
Out[7]: 2
In [8]: cnn.poll()
Out[8]: 1
In [9]: cnn.poll()
Out[9]: 0
In [12]: cur.execute("copy (select 1 as x) to stdout")
In [14]: cnn.poll()
^C -- hung
So yes, I'll take a look if there is a way to detect we get in this state.
But I'm not sure it's possible, because we might not have received a result
yet that tells we are in a state not allowed (in a COPY).
Observation: maybe EnterpriseDB has resources enough to help us debugging
and fixing this issue, or maybe even implement async copy?
-- Daniele
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Copy command hangs in poll() function
2018-10-04 05:35 Copy command hangs in poll() function Akshay Joshi <[email protected]>
2018-10-04 10:26 ` Re: Copy command hangs in poll() function Daniele Varrazzo <[email protected]>
@ 2018-10-04 10:29 ` Daniele Varrazzo <[email protected]>
1 sibling, 0 replies; 4+ messages in thread
From: Daniele Varrazzo @ 2018-10-04 10:29 UTC (permalink / raw)
To: [email protected]; +Cc: psycopg
On Thu, Oct 4, 2018 at 11:26 AM Daniele Varrazzo
<[email protected]> wrote:
> Uhm, I see:
Issue https://github.com/psycopg/psycopg2/issues/781 opened.
-- Daniele
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Copy command hangs in poll() function
2018-10-04 05:35 Copy command hangs in poll() function Akshay Joshi <[email protected]>
2018-10-04 10:26 ` Re: Copy command hangs in poll() function Daniele Varrazzo <[email protected]>
@ 2018-10-04 10:33 ` Federico Di Gregorio <[email protected]>
1 sibling, 0 replies; 4+ messages in thread
From: Federico Di Gregorio @ 2018-10-04 10:33 UTC (permalink / raw)
To: Daniele Varrazzo <[email protected]>; [email protected]; +Cc: psycopg
On 10/04/2018 12:26 PM, Daniele Varrazzo wrote:
> On Thu, Oct 4, 2018 at 6:35 AM Akshay Joshi
> <[email protected] <mailto:[email protected]>>
> wrote:
>
> Hello
>
> As per documentation http://initd.org/psycopg/docs/advanced.html
> <http://initd.org/psycopg/docs/advanced.html> Copy commands are not
> supported in asynchronous mode, but this will be probably
> implemented in a future release. In pgAdmin4 (open source) we have
> used async connection to run the SQL query on PostgreSQL database
> and uses poll() function to poll the results. When user runs any
> *COPY *command application hangs at poll() function.
>
>
> If copy command not supported then at least it should not hang the
> application. poll() function should return the proper error message.
>
> Can you please provide that fix until support for copy command won't
> come.
>
>
> Uhm, I see:
>
> In [2]: cnn = psycopg2.connect("")
> In [3]: cur = cnn.cursor()
> In [4]: cur.execute("copy (select 1 as x) to stdout")
>
> ---------------------------------------------------------------------------
> ProgrammingError Traceback (most recent
> call last)
> <ipython-input-4-62e3af3d121e> in <module>()
> ----> 1 cur.execute("copy (select 1 as x) to stdout")
> ProgrammingError: can't execute COPY TO: use the copy_to() method
> instead
>
> but:
>
> In [6]: cnn = psycopg2.connect("", async=True)
> In [7]: cnn.poll()
> Out[7]: 2
> In [8]: cnn.poll()
> Out[8]: 1
> In [9]: cnn.poll()
> Out[9]: 0
>
> In [12]: cur.execute("copy (select 1 as x) to stdout")
> In [14]: cnn.poll()
> ^C -- hung
>
> So yes, I'll take a look if there is a way to detect we get in this
> state. But I'm not sure it's possible, because we might not have
> received a result yet that tells we are in a state not allowed (in a COPY).
>
> Observation: maybe EnterpriseDB has resources enough to help us
> debugging and fixing this issue, or maybe even implement async copy?
Also, let me add that if the only way to detect the situation is by
analyzing the query, we'll never do that.
Also, IMHO, it is perfectly fine that a sequence of operations that is
documented as "not working" hangs - it is not something you can do by
error: you're ignoring the documentation.
federico
--
Federico Di Gregorio [email protected]
DNDG srl http://dndg.it
I filosofi son come i sociologi: il mondo non lo capiscono. -- A.R.M.
^ permalink raw reply [nested|flat] 4+ messages in thread
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2018-10-04 05:35 Copy command hangs in poll() function Akshay Joshi <[email protected]>
2018-10-04 10:26 ` Daniele Varrazzo <[email protected]>
2018-10-04 10:29 ` Daniele Varrazzo <[email protected]>
2018-10-04 10:33 ` Federico Di Gregorio <[email protected]>
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