Packet types : optional. If specified, a comma-separated list of packet types for which this filter should be called, for instance: Parse,Bind,Close. Spaces are ignored.
log : the log object
context : contains all the variables you'll commonly use:
packet : the packet being filtered
result : the result object, used to cancel the current packet if desired
filterContext: an object containing variables attached to this filter. Any changes to this object will be visible to all invocations of this filter.
connectionContext: an object containing variables attached to the connection. Any changes to this object will be visible to all filters defined on this connection.
When connecting, it's common for a database client to issue the command set extra_float_digits = n (Postgres documentation). We could force it to a different value with the following filter defined for Parse packets: