Re: [GENERAL] libpq confusion

[Thomas Delrue]

On Wednesday, September 20, 2017 1:47:05 PM EDT Igor Korot wrote:
>Thx.
>So it is referring to the command not a "command returning no data". ;-)

assuming
create table t (c int);

select c from t;
- PQresultStatus(result) == PGRES_TUPLES_OK
- PQntuples(result) == number or rows returned (int)
insert into t(c)values(1);
- PQresultStatus(result) ==PGRES_COMMAND_OK
- PQcmdTuples(result) == "1" (note: char*)
insert into t(c)values(1) returning c;
- PQresultStatus(result) ==PGRES_TUPLES_OK
- PQntuples(result) == 1 (int)

>On Wed, Sep 20, 2017 at 1:42 PM, John R Pierce  wrote:
>> On 9/20/2017 10:34 AM, Igor Korot wrote:
>> >From the documentation:
>> https://www.postgresql.org/docs/9.1/static/libpq-exec.html
>> 
>> [quote]
>> PGRES_COMMAND_OK
>> 
>> Successful completion of a command returning no data.
>> [/quote]
>> 
>> No data = no rows, right?
>> 
>> from that same page, a bit farther down, clarifying the potentially
>> confusing wording.
>> 
>> If the result status is PGRES_TUPLES_OK, then the functions described below
>> can be used to retrieve the rows returned by the query. Note that a SELECT
>> command that happens to retrieve zero rows still shows PGRES_TUPLES_OK.
>> PGRES_COMMAND_OK is for commands that can never return rows (INSERT,
>> UPDATE,
>> etc.). A response of PGRES_EMPTY_QUERY might indicate a bug in the client
>> software.


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Re: [GENERAL] libpq confusion

[Igor Korot]

Thx.
So it is referring to the command not a "command returning no data". ;-)

On Wed, Sep 20, 2017 at 1:42 PM, John R Pierce  wrote:
> On 9/20/2017 10:34 AM, Igor Korot wrote:
>
> >From the documentation:
> https://www.postgresql.org/docs/9.1/static/libpq-exec.html
>
> [quote]
> PGRES_COMMAND_OK
>
> Successful completion of a command returning no data.
> [/quote]
>
> No data = no rows, right?
>
> from that same page, a bit farther down, clarifying the potentially
> confusing wording.
>
> If the result status is PGRES_TUPLES_OK, then the functions described below
> can be used to retrieve the rows returned by the query. Note that a SELECT
> command that happens to retrieve zero rows still shows PGRES_TUPLES_OK.
> PGRES_COMMAND_OK is for commands that can never return rows (INSERT, UPDATE,
> etc.). A response of PGRES_EMPTY_QUERY might indicate a bug in the client
> software.
>
>
> --
> john r pierce, recycling bits in santa cruz


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Re: [GENERAL] libpq confusion

[John R Pierce]

On 9/20/2017 10:34 AM, Igor Korot wrote:

>From the documentation:
https://www.postgresql.org/docs/9.1/static/libpq-exec.html

[quote]
PGRES_COMMAND_OK

Successful completion of a command returning no data.
[/quote]

No data = no rows, right?


from that same page, a bit farther down, clarifying the potentially 
confusing wording.


   If the result status isPGRES_TUPLES_OK, then the functions described
   below can be used to retrieve the rows returned by the query. Note
   that aSELECTcommand that happens to retrieve zero rows still
   showsPGRES_TUPLES_OK.PGRES_COMMAND_OKis for commands that can never
   return rows (INSERT,UPDATE, etc.). A response
   ofPGRES_EMPTY_QUERYmight indicate a bug in the client software.


--
john r pierce, recycling bits in santa cruz

Re: [GENERAL] libpq confusion

[Igor Korot]

Hi, John,

On Wed, Sep 20, 2017 at 12:02 PM, John R Pierce  wrote:
> On 9/20/2017 6:30 AM, Igor Korot wrote:
>
> Hi, guys,
>
> On Wed, Sep 20, 2017 at 12:20 AM, Allan Harvey
>  wrote:
>
> How do I properly check if the record exists from libpq?
>
> Igor,
> I use PQntuples() to check the number of ... tuples, for > 0
>
> I was actually curious - isn't it what "PGRES_COMMAND_OK" for?
> IIUC, this constant indicates successful query run, but no records was
> generated.
>
> Or am I missing something and I will have to check PQntuples()?
>
>
> a query that returns zero rows is still successful.

>From the documentation:
https://www.postgresql.org/docs/9.1/static/libpq-exec.html

[quote]
PGRES_COMMAND_OK

Successful completion of a command returning no data.
[/quote]

No data = no rows, right?

Thank you.


>
> --
> john r pierce, recycling bits in santa cruz


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Re: [GENERAL] libpq confusion

[John R Pierce]

On 9/20/2017 6:30 AM, Igor Korot wrote:

Hi, guys,

On Wed, Sep 20, 2017 at 12:20 AM, Allan Harvey
  wrote:

How do I properly check if the record exists from libpq?

Igor,
I use PQntuples() to check the number of ... tuples, for > 0

I was actually curious - isn't it what "PGRES_COMMAND_OK" for?
IIUC, this constant indicates successful query run, but no records was
generated.

Or am I missing something and I will have to check PQntuples()?



a query that returns zero rows is still successful.

--
john r pierce, recycling bits in santa cruz

Re: [GENERAL] libpq confusion

[Allan Harvey]

>How do I properly check if the record exists from libpq?

Igor,
I use PQntuples() to check the number of ... tuples, for > 0

Allan

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Re: [GENERAL] libpq confusion

[Igor Korot]

Hi, guys,

On Wed, Sep 20, 2017 at 12:20 AM, Allan Harvey
 wrote:
>
>>How do I properly check if the record exists from libpq?
>
> Igor,
> I use PQntuples() to check the number of ... tuples, for > 0

I was actually curious - isn't it what "PGRES_COMMAND_OK" for?
IIUC, this constant indicates successful query run, but no records was
generated.

Or am I missing something and I will have to check PQntuples()?

Thank you.

>
> Allan
>
> __
> This e-mail message may contain confidential or legally privileged 
> information and is only for the use of the intended recipient(s). Any 
> unauthorized disclosure, dissemination, distribution, copying or the taking 
> of any action in reliance on the information herein is prohibited. E-mails 
> are not secure and cannot be guaranteed to be error free as they can be 
> intercepted, amended, or contain viruses. Anyone who communicates with us by 
> e-mail is deemed to have accepted these risks. GFG Alliance Australia and its 
> related bodies corporate and the sender are not responsible for errors or 
> omissions in this message and deny any responsibility for any damage arising 
> from the use of this e-mail. Any opinion and other statement contained in 
> this message and any attachment are solely those of the author and do not 
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Re: [GENERAL] libpq confusion

[Pavel Stehule]

2017-09-20 5:36 GMT+02:00 Igor Korot :

> Hi, ALL,
>
> draft=# SELECT 1 FROM abcattbl WHERE abt_tnam = 'leagues';
>  ?column?
> --
> (0 rows)
>
>
> However running it thru the PQexecParam() I am getting "PGRES_TUPLES_OK"
> which means that the such record exist.
>

That means so this command doesn't fail  - not so there  are some record.

you can use different query, that returns true, false

SELECT EXISTS(SELECT * FROM abcattbl WHERE abt_tnam = 'leagues');

Regards

Pavel


> How do I properly check if the record exists from libpq?
>
>
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