Обсуждение: Retrieve all the returned rows in one call

I am right now using the libpq interface and struggling with efficiently 
retrieve the result from a query.

Let's say I run a select statement with some where clauses and then retrieve 
the result into a PGresult. I want to know if there is an efficient way to 
retrieve all the rows at once? I am going to return a char*** from my 
function, i.e. a two-dimensional array of char pointers.
I have seen the COPY sql command, but up to v8.1 i cannot use a select 
statement with it, the only way to customize COPY is to choose which columns 
to return, but still, the only option is to return the whole table. 
Furthermore, when using PQgetCopyData I get the whole row at once, but I 
still have to loop through all rows.
I have also seen in the PGresult structure that it has a member called 
tuples, which is a two-dimensional array of the structure PGresAttValue. 
This is a way to recieve all the data at once, but it is in a format which 
is specific for PostgreSQL and I am developing a database interface 
including other databases two, so I want to use a general structure returned 
from the function, i.e. a char***. This means that I would have to loop 
through the tuples array to convert into the char array structure, and hence 
lose the whole meaning with recieving all the rows at once.

So my question is if it is possible in any way to retrieve the result in the 
form of char***?

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On Monday 09 October 2006 10:58, Andreas Gidlund wrote:
> I am right now using the libpq interface and struggling with efficiently
> retrieve the result from a query.
>
> Let's say I run a select statement with some where clauses and then
> retrieve the result into a PGresult. I want to know if there is an
> efficient way to retrieve all the rows at once? I am going to return a
> char*** from my function, i.e. a two-dimensional array of char pointers.
> I have seen the COPY sql command, but up to v8.1 i cannot use a select
> statement with it, the only way to customize COPY is to choose which
> columns to return, but still, the only option is to return the whole table.
> Furthermore, when using PQgetCopyData I get the whole row at once, but I
> still have to loop through all rows.
> I have also seen in the PGresult structure that it has a member called
> tuples, which is a two-dimensional array of the structure PGresAttValue.
> This is a way to recieve all the data at once, but it is in a format which
> is specific for PostgreSQL and I am developing a database interface
> including other databases two, so I want to use a general structure
> returned from the function, i.e. a char***. This means that I would have to
> loop through the tuples array to convert into the char array structure, and
> hence lose the whole meaning with recieving all the rows at once.
>
> So my question is if it is possible in any way to retrieve the result in
> the form of char***?

I think the answer is no.  

Sean