On Thu, 2019-10-17 at 11:16 +0000, M Tarkeshwar Rao wrote:
> [EXTERNAL SOURCE]
>
>
>
> Hi all,
>
> How to fetch certain number of tuples from a postgres table.
>
> Same I am doing in oracle using following lines by setting prefetch attribute.
>
> For oracle
> // Prepare query
> if( OCIStmtPrepare( myOciStatement, myOciError, (text *)aSqlStatement,
> // Get statement type
> OCIAttrGet( (void *)myOciStatement, OCI_HTYPE_STMT, &statement_type, 0, OCI_ATTR_STMT_TYPE, myOciError );
> // Set prefetch count
> OCIAttrSet( myOciStatement, OCI_HTYPE_STMT, &prefetch, 0, OCI_ATTR_PREFETCH_ROWS, myOciError );
> // Execute query
> status = OCIStmtExecute( myOciServerCtx, myOciStatement, myOciError, iters, 0, NULL, NULL, OCI_DEFAULT );
>
>
> For Postgres
>
> Can you please tell us how set this prefetch attribute in following lines. Is PQexec returns all the rows from the table?
>
> mySqlResultsPG = PQexec(connection, aSqlStatement);
> if((PQresultStatus(mySqlResultsPG) == PGRES_FATAL_ERROR ) || (PQstatus(connection) != CONNECTION_OK)){}
> if ((PQresultStatus(mySqlResultsPG) == PGRES_COMMAND_OK) || (PQresultStatus(mySqlResultsPG) == PGRES_TUPLES_OK))
> {
> myNumColumns = PQnfields(mySqlResultsPG);
> myTotalNumberOfRowsInQueryResult = PQntuples(mySqlResultsPG);
> myCurrentRowNum = 0 ;
> }
>
>
> Regards
> Tarkeshwar
>
declare a cursor and fetch
https://books.google.com/books?id=Nc5ZT2X5mOcC&pg=PA405&lpg=PA405&dq=pqexec+fetch&source=bl&ots=8P8w5JemcL&sig=ACfU3U0POGGSP0tYTrs5oxykJdOeffaspA&hl=en&sa=X&ved=2ahUKEwjevbmA2KPlAhXukOAKHaBIBcoQ6AEwCnoECDEQAQ#v=onepage&q=pqexec%20fetch&f=false