Database Connection Control Functions

There are database connection control functions for controlling the connections to database servers. An application can connect to multiple servers at a time. For example, a client connects to multiple databases. Each connection is represented by a PGconn object, which is obtained from the function PQconnectdb, PQconnectdbParams, or PQsetdbLogin. You can also obtain a connection object by using the PQconnectStart API together with the asynchronous PQconnectPoll polling method. Note that these functions will always return a non-null object pointer, unless memory allocation fails. The API for establishing a connection is stored in the PGconn object. The PQstatus function can be called to check the return value for a successful connection. The PGconn object stores the SSL context in a local thread. Therefore, the PGconn released thread must be the same as the allocated thread.