Connection Characters

Table 1 Connection strings

Character String	Description
host	Name of the host to connect to. If the host name starts with a slash (/), Unix-domain socket communications instead of TCP/IP communications are used. The value is the directory where the socket file is stored. If host is not specified, the default behavior is to connect to the Unix-domain socket in the /tmp directory (or the socket directory specified during MogDB installation). On a machine without a Unix-domain socket, the default behavior is to connect to localhost.
hostaddr	IP address of the host to connect to. The value is in standard IPv4 address format, for example, 172.28.40.9. If your machine supports IPv6, IPv6 address can also be used. If a non-null string is specified, TCP/IP communications are used. Replacing host with hostaddr can prevent applications from querying host names, which may be important for applications with time constraints. However, a host name is required for GSSAPI or SSPI authentication methods. Therefore, the following rules are used: 1. If host is specified but hostaddr is not, a query for the host name will be executed. 2. If hostaddr is specified but host is not, the value of hostaddr is the server network address. If the host name is required by authentication, the connection attempt fails. 3. If both host and hostaddr are specified, the value of hostaddr is the server network address. The value of host is ignored unless it is required by authentication, in which case it is used as the host name. NOTICE: - If host is not the server name in the network address specified by hostaddr, the authentication may fail. - If neither host nor hostaddr is specified, libpq will use a local Unix-domain socket for connection. If the machine does not have a Unix-domain socket, it will attempt to connect to localhost.
port	Port number of the host server, or the socket file name extension for Unix-domain connections.
user	Name of the user to connect as. By default, the username is the same as the operating system name of the user running the application.
dbname	Database name. The default value is the same as the username.
password	Password to be used if the server requires password authentication.
connect_timeout	Maximum timeout period of the connection, in seconds (in decimal integer string). The value 0 or null indicates infinity. You are not advised to set the connection timeout period to a value less than 2 seconds.
client_encoding	Client encoding for the connection. In addition to the values accepted by the corresponding server options, you can use auto to determine the correct encoding from the current environment in the client (the LC_CTYPE environment variable in the Unix system).
options	Adds command-line options to send to the server at runtime.
application_name	Current user identity.
keepalives	Whether TCP keepalive is enabled on the client side. The default value is 1, indicating that the function is enabled. The value 0 indicates that the function is disabled. Ignore this parameter for Unix-domain connections.
keepalives_idle	The number of seconds of inactivity after which TCP should send a keepalive message to the server. The value 0 indicates that the default value is used. Ignore this parameter for Unix-domain connections or if keep-alive is disabled.
keepalives_interval	The number of seconds after which a TCP keepalive message that is not acknowledged by the server should be retransmitted. The value 0 indicates that the default value is used. Ignore this parameter for Unix-domain connections or if keep-alive is disabled.
keepalives_count	Adds command-line options to send to the server at runtime. For example, adding -c comm_debug_mode=off to set the value of the GUC parameter comm_debug_mode to off.