pg_get_prepared?

Hi,

On 7/15/05, Christopher Kings-Lynne <chriskl@familyhealth.com.au> wrote:

Would it be useful to have a pg_get_prepared(name) function that returns
true or false depending on whether or not there is a prepared query of
that name?

(You're mentioning about PHP PostgreSQL API, right?) I couldn't see
any proper usage area for this. Can you give some examples?

Furthermore, I wondered the steps you'll follow to achieve this. How
will you check if a prepared stmt exists or not?

Regards.

Volkan YAZICI wrote:

Hi,

On 7/15/05, Christopher Kings-Lynne <chriskl@familyhealth.com.au> wrote:

Would it be useful to have a pg_get_prepared(name) function that returns
true or false depending on whether or not there is a prepared query of
that name?

(You're mentioning about PHP PostgreSQL API, right?) I couldn't see
any proper usage area for this. Can you give some examples?

No, I'm talking about a PostgreSQL backend function.

The use case is when you want to prepare a query, but only if it's not
already prepared on that connection.

Furthermore, I wondered the steps you'll follow to achieve this. How
will you check if a prepared stmt exists or not?

Same way that the EXECUTE command checks...

Chris

Christopher Kings-Lynne wrote:

Would it be useful to have a pg_get_prepared(name) function that returns
true or false depending on whether or not there is a prepared query of
that name?

From the TODO:

* Allow pooled connections to list all prepared queries

So this has been raised before.

-Neil

On 7/15/05, Christopher Kings-Lynne <chriskl@familyhealth.com.au> wrote:

You're mentioning about PHP PostgreSQL API, right?

No, I'm talking about a PostgreSQL backend function.

Sorry, when you give a name like pg_get_prepared() (which is used in
PHP PostgreSQL API functions), I thought it's for PHP too.

The use case is when you want to prepare a query, but only if it's not
already prepared on that connection.

As Neil Conway explained on IRC - this feature can be useful for
connection pools. E.g. avoid re-preparing a stmt. if a previous client
using the conn. already prepared it.

Same way that the EXECUTE command checks.

If it'll be done from backend, then there's no problem. I wondered the
PHP side of it. Anyway, it wasn't a PHP function.

Regards.

Christopher Kings-Lynne <chriskl@familyhealth.com.au> writes:

Would it be useful to have a pg_get_prepared(name) function that returns
true or false depending on whether or not there is a prepared query of
that name?

This has been discussed as something needed at the protocol level, not
a SQL function.

Perhaps we could have a way of checking the parameter types of it as well?

That's called Describe Statement.

regards, tom lane

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The use case is when you want to prepare a query, but only if it's not
already prepared on that connection.

This has been covered before, but to reiterate: why would you need this?
Any application worth its salt should be tracking which statements it
has already prepared (after all, they cannot span connections). Seems
a waste of resources to make a separate call to the database for
information you should already know.

- --
Greg Sabino Mullane greg@turnstep.com
PGP Key: 0x14964AC8 200507151017
https://www.biglumber.com/x/web?pk=2529DF6AB8F79407E94445B4BC9B906714964AC8

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This has been covered before, but to reiterate: why would you need this?
Any application worth its salt should be tracking which statements it
has already prepared (after all, they cannot span connections). Seems
a waste of resources to make a separate call to the database for
information you should already know.

Erm, websites...use persistent connections...you have no idea if you're
dealing with a new connection or a reused one, and if the statement is
prepared or not.

Chris

Am Freitag, 15. Juli 2005 14:19 schrieb Greg Sabino Mullane:

The use case is when you want to prepare a query, but only if it's not
already prepared on that connection.

This has been covered before, but to reiterate: why would you need this?
Any application worth its salt should be tracking which statements it
has already prepared (after all, they cannot span connections). Seems
a waste of resources to make a separate call to the database for
information you should already know.

Does not apply to mod_php/apache, you simply do not know if a connection made
my pg_pconnect is a new connection or a reused one. That has nothing to do
with the application itself.

On Sat, 16 Jul 2005, Christopher Kings-Lynne wrote:

This has been covered before, but to reiterate: why would you need this?
Any application worth its salt should be tracking which statements it
has already prepared (after all, they cannot span connections). Seems
a waste of resources to make a separate call to the database for
information you should already know.

Erm, websites...use persistent connections...you have no idea if you're
dealing with a new connection or a reused one, and if the statement is
prepared or not.

I think the point is that this is the driver's problem, not the
applications. If you are using SQL level PREPARE/EXECUTE in your code
that's your problem, but if you are using an api like:

$stmt = $conn->prepare("SELECT * FROM tab WHERE x = ?");
$result = $stmt->execute(71);

Then the driver itself should know if the above query has been prepared
previously and further what type it has been prepared for so that it can
cast the 71 or prepare a new statement.

Kris Jurka