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2.15 Contents of RWDBSystemHandle
The RWDBConnection::systemHandle() method returns a pointer to a base class from which a family of implementation-specific classes is derived. To use the database API directly, an application can downcast this pointer to the appropriate type, and use its implementation-specific features. Naturally, this usage reduces an application's portability.
For a PostgreSQL connection, the implementation-specific system handle has the data type RWDBPGSSystemHandle. It contains the PGconn* used by the RWDBConnection. The following method may be used to retrieve this component:
PGconn* dbc()const;
2.15.1 Rows per Cursor Fetch
To improve the performance of cursor result sets, the PostgreSQL Access Module fetches n number of rows from the server in a single call and buffers them internally. The default value of n is 10.
The number of rows fetched for cursor result sets can be altered through the following methods:
RWDBStatus rowsPerCursorFetch(unsigned long value); unsigned long rowsPerCursorFetch() const;
2.15.2 Using RWDBSystemHandle
If it is necessary for your application to make calls directly to the PostgreSQL libpq API, proceed as in the following example:
Example 7: Calling the PostgreSQL libpq API directly
#include <rw/db/pgssrc/pgsdefs.h>
#include <rw/db/pgssrc/pgssysh.h>
RWDBConnection connect = myDbase.connection();
RWDBPGSSystemHandle* handle = (RWDBPGSSystemHandle *)
connect.systemHandle();
PGconn* dbc = handle->dbc();
// Use dbc for PostgreSQL libpq API calls.
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