libpq confusion

2017-09-20 5:36 GMT+02:00 Igor Korot <ikorot01@gmail.com>:

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?

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

Allan

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Hi, guys,

On Wed, Sep 20, 2017 at 12:20 AM, Allan Harvey
<allan.harvey@libertyonesteel.com> 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

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

Hi, guys,

On Wed, Sep 20, 2017 at 12:20 AM, Allan Harvey
<allan.harvey@libertyonesteel.com> 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.

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john r pierce, recycling bits in santa cruz

Hi, John,

On Wed, Sep 20, 2017 at 12:02 PM, John R Pierce <pierce@hogranch.com> wrote:

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

Hi, guys,

On Wed, Sep 20, 2017 at 12:20 AM, Allan Harvey
<allan.harvey@libertyonesteel.com> 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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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

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 <pierce@hogranch.com> 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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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)