| Overview |  |
See also: epgsql_cmd_connect for network connection and authentication setup.
GenServer holding all the connection state (including socket).
See https://www.postgresql.org/docs/current/static/protocol-flow.html
Commands in PostgreSQL protocol are pipelined: you don't have to wait for reply to be able to send next command. Commands are processed (and responses to them are generated) in FIFO order. eg, if you execute 2 SimpleQuery: #1 and #2, first you get all response packets for #1 and then all for #2:> SQuery #1 > SQuery #2 < RowDescription #1 < DataRow #1.1 < ... < DataRow #1.N < CommandComplete #1 < RowDescription #2 < DataRow #2.1 < ... < DataRow #2.N < CommandComplete #2
epgsql_sock is capable of utilizing the pipelining feature - as soon as
it receives a new command, it sends it to the server immediately and then
it puts command's callbacks and state into internal queue of all the commands
which were sent to the server and waiting for response. So it knows in which
order it should call each pipelined command's handle_message callback.
But it can be easily broken if high-level command is poorly implemented or
some conflicting low-level commands (such as parse, bind, execute) are
executed in a wrong order. In this case server and epgsql states become out of
sync and epgsql_cmd_sync have to be executed in order to recover.
epgsql_cmd_copy_from_stdin and epgsql_cmd_start_replication switches the
"state machine" of connection process to a special "COPY mode" subprotocol.
See https://www.postgresql.org/docs/current/protocol-flow.html#PROTOCOL-COPY.
copy_state() = #copy{initiator = pid(), last_error = undefined | epgsql:query_error(), format = binary | text, binary_types = [epgsql:epgsql_type()] | undefined}
error() = {error, sync_required | closed | sock_closed | sock_error}
abstract datatype: pg_sock()
repl_state() = #repl{last_received_lsn = integer() | undefined, last_flushed_lsn = integer() | undefined, last_applied_lsn = integer() | undefined, feedback_required = boolean() | undefined, cbmodule = module() | undefined, cbstate = any() | undefined, receiver = pid() | undefined, align_lsn = boolean() | undefined}
tcp_socket() = port()
gen_tcp:socket() isn't exported prior to erl 18
transport() = {call, any()} | {cast, pid(), reference()} | {incremental, pid(), reference()}
async_command(C::epgsql:connection(), Transport::cast | incremental, Command::epgsql_command:command(), Args::any()) -> reference()
cancel(S) -> any()
close(C) -> any()
code_change(OldVsn, State, Extra) -> any()
copy_send_rows(C, Rows, Timeout) -> any()
format_status(X1, X2) -> any()
get_cmd_status(C) -> any()
get_codec(State::pg_sock()) -> epgsql_binary:codec()
get_parameter(C, Name) -> any()
get_parameter_internal(Name::binary(), State::pg_sock()) -> binary() | undefined
get_results(State::pg_sock()) -> [any()]
get_rows(State::pg_sock()) -> [tuple()]
get_subproto_state(State::pg_sock()) -> repl_state() | copy_state() | undefined
handle_call(X1, From, State) -> any()
handle_cast(X1, State) -> any()
handle_info(X1, State) -> any()
init(X1) -> any()
notify(State, Notice) -> any()
on_copy_from_stdin(M, Err, State) -> any()
Handle "copy subprotocol" for COPY .. FROM STDIN
Activated byepgsql_cmd_copy_from_stdin, deactivated by epgsql_cmd_copy_done or error
on_message(Msg, Bin, State) -> any()
on_replication(M, Err, State) -> any()
send(State::pg_sock(), Data::iodata()) -> ok | {error, any()}
send(State::pg_sock(), Type::epgsql_wire:packet_type(), Data::iodata()) -> ok | {error, any()}
send_multi(State::pg_sock(), List::[{epgsql_wire:packet_type(), iodata()}]) -> ok | {error, any()}
set_net_socket(Mod::gen_tcp | ssl, Socket::tcp_socket() | ssl:sslsocket(), State::pg_sock()) -> pg_sock()
set_notice_receiver(C, PidOrName) -> any()
standby_status_update(C, FlushedLSN, AppliedLSN) -> any()
start_link() -> any()
sync_command(C::epgsql:connection(), Command::epgsql_command:command(), Args::any()) -> any()
terminate(Reason, State) -> any()
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