MIME-Version: 1.0
In-Reply-To: 
 <CAM5-9D8EB1vjrCPBU0ygOYzxahq-y1pVa6AheFaCG91y4M0hdA@mail.gmail.com>
References: 
 <CAM5-9D-ZEfmyouAYrrM8V00AccPup0Uu_6vw48GQaDvWk_jW8Q@mail.gmail.com>
 <CA+OCxoyUdxLTM-X8+wVjTngOR5X+RL4o+WK8DF=M3EOa3Md=ag@mail.gmail.com>
 <CAM5-9D_CmhAW3ePLK90hifKKzvqrPBVfa3+BG0H1=1_D16jFQA@mail.gmail.com>
 <CAM5-9D8EB1vjrCPBU0ygOYzxahq-y1pVa6AheFaCG91y4M0hdA@mail.gmail.com>
From: Dave Page <dpage@pgadmin.org>
Date: Tue, 20 Sep 2016 10:03:14 +0100
Message-ID: 
 <CA+OCxowDBRdcC318VnyvHmkZ_2OGjdOvdSMUsJ5x-96aarXwgQ@mail.gmail.com>
Subject: Re: [pgAdmin4][Patch]: RM1592 - Download as CSV
 should be supported for DDL
To: Surinder Kumar <surinder.kumar@enterprisedb.com>
Cc: pgadmin-hackers <pgadmin-hackers@postgresql.org>
Content-Type: text/plain; charset=UTF-8
Precedence: bulk
Sender: pgadmin-hackers-owner@postgresql.org

On Tue, Sep 20, 2016 at 6:43 AM, Surinder Kumar
<surinder.kumar@enterprisedb.com> wrote:
>
> On Mon, Sep 19, 2016 at 8:59 PM, Surinder Kumar
> <surinder.kumar@enterprisedb.com> wrote:
>>
>> On Mon, Sep 19, 2016 at 8:48 PM, Dave Page <dpage@pgadmin.org> wrote:
>>>
>>> Hi
>>>
>>> On Mon, Sep 19, 2016 at 3:03 PM, Surinder Kumar
>>> <surinder.kumar@enterprisedb.com> wrote:
>>> > Hi
>>> >
>>> > Please find attached patch with fix.
>>> >>
>>> >> Download as CSV
>>> >>  button should be enabled only for SELECT queries.
>>>
>>> I'm not sure there's a way to do this without parsing the query.
>>> Simply matching on ^select certainly won't work reliably - for
>>> example, there could be multiple statements in the script, or it could
>>> be PERFORM ...  or UPDATE ... RETURNING ...
>>
>> I wasn't aware of such cases.
>>>
>>>
>>> I think we need to leave the button enabled, but give the user a
>>> message if no data is returned, e.g.
>>
>> ok. sure.
>
> I discussed the issue with Harshal and this is how download csv works:
> We just hit the url to download csv, and let the browser handle the response
> from the server side. we don't have access to response data to check if no
> data is returned.

Hmm, yeah that's true.

> The other approach is to hit the same query twice. First time an ajax query
> to check if data is returned or not. if returned, fire another query to
> download csv otherwise set message in message panel.
> But the limitation with this approach is that we are just increasing load
> over server by hitting same query twice, incase returned data rows in
> billions.
> Thoughts ?

Yeah, we can't do that.

The only thing I can think of right now is to simply write the error
message to the CSV file, e.g.

"The query executed did not return any data."

(with the quotes, so it's valid CSV). That way at least the user will
always get a file downloaded, and will see the error when they open
it.

-- 
Dave Page
Blog: http://pgsnake.blogspot.com
Twitter: @pgsnake

EnterpriseDB UK: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


-- 
Sent via pgadmin-hackers mailing list (pgadmin-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgadmin-hackers