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postgresql.pl
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postgresql.pl
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:- module(postgresql, [connect/6, query/3, query/4, sql/3]).
:- use_module(library(lists)).
:- use_module(library(charsio)).
:- use_module(library(sockets)).
:- use_module('messages').
:- use_module('sql_query').
:- use_module('types').
connect(User, Password, Host, Port, Database, postgresql(Stream)) :-
socket_client_open(Host:Port, Stream, [type(binary)]),
startup_message(User, Database, BytesStartup),
put_bytes(Stream, BytesStartup),
get_bytes(Stream, BytesAuth),
auth_message(password, BytesAuth),
password_message(Password, BytesPassword),
put_bytes(Stream, BytesPassword),
get_bytes(Stream, BytesOk),
auth_ok_message(BytesOk),
flush_bytes(Stream).
flush_bytes(Stream) :-
get_bytes(Stream, Bytes),
(
Bytes = [90|_] ->
true
; flush_bytes(Stream)
).
query(postgresql(Stream), Query, Result) :-
query_message(Query, BytesQuery),
put_bytes(Stream, BytesQuery),
get_bytes(Stream, BytesResponse),
try_query_response(Stream, BytesResponse, Result).
% after a query message, the following messages can be received
% - CommandComplete
% - RowDescription -> N DataRow
% - EmptyQueryResponse
% - ErrorResponse
% - NoticeResponse
% and then a ReadyForQuery message
try_query_response(Stream, BytesResponse, Result) :-
command_complete_message(BytesResponse),!,
Result = ok,
get_bytes(Stream, BytesEnd),
ready_for_query_message(BytesEnd).
try_query_response(Stream, BytesResponse, Result) :-
row_description_message(ColumnsDescription, BytesResponse),!,
% then zero or more data rows
get_bytes(Stream, BytesData),
get_data_rows(Stream, ColumnsData, BytesData),
Result = data(ColumnsDescription, ColumnsData).
% until we get a command complete message
try_query_response(Stream, BytesResponse, Result) :-
empty_query_message(BytesResponse),!,
Result = [],
get_bytes(Stream, BytesEnd),
ready_for_query_message(BytesEnd).
try_query_response(Stream, BytesResponse, Result) :-
error_message(Error, BytesResponse),!,
Result = error(Error),
get_bytes(Stream, BytesEnd),
ready_for_query_message(BytesEnd).
try_query_response(Stream, BytesResponse, Result) :-
notice_message(BytesResponse),!,
get_bytes(Stream, BytesResponse0),
try_query_response(Stream, BytesResponse0, Result).
get_data_rows(Stream, [], BytesData) :-
command_complete_message(BytesData),!,
get_bytes(Stream, BytesData0),
ready_for_query_message(BytesData0).
get_data_rows(Stream, [Column|Columns], BytesData) :-
data_row_message(Column, BytesData),!,
get_bytes(Stream, BytesData0),
get_data_rows(Stream, Columns, BytesData0).
% Extended Query. Safer
query(postgresql(Stream), Query, Params, Result) :-
length(Params, NumberParams),
parse_message(Query, NumberParams, QueryBytes),
put_bytes(Stream, QueryBytes),
flush_message(FlushBytes),
put_bytes(Stream, FlushBytes),
get_bytes(Stream, ResponseBytes),
try_parse_response(Stream, ResponseBytes, Params, Result).
try_parse_response(Stream, BytesData, Params, Result) :-
parse_complete_message(BytesData),!,
bind_message(Params, BindBytes),
put_bytes(Stream, BindBytes),
flush_message(FlushBytes),
put_bytes(Stream, FlushBytes),
get_bytes(Stream, ResponseBytes),
try_bind_response(Stream, ResponseBytes, Result).
try_parse_response(Stream, BytesResponse, _, Result) :-
error_message(Error, BytesResponse),!,
Result = error(Error),
sync_message(SyncBytes),
put_bytes(Stream, SyncBytes),
get_bytes(Stream, BytesEnd),
ready_for_query_message(BytesEnd).
try_bind_response(Stream, BytesData, Result) :-
bind_complete_message(BytesData),!,
execute_message(ExecuteBytes),
put_bytes(Stream, ExecuteBytes),
flush_message(FlushBytes),
put_bytes(Stream, FlushBytes),
get_bytes(Stream, ResponseBytes),
try_execute_response(Stream, ResponseBytes, Result).
try_bind_response(Stream, BytesResponse, _, Result) :-
error_message(Error, BytesResponse),!,
Result = error(Error),
sync_message(SyncBytes),
put_bytes(Stream, SyncBytes),
get_bytes(Stream, BytesEnd),
ready_for_query_message(BytesEnd).
try_execute_response(Stream, BytesResponse, Result) :-
ext_get_data_rows(Stream, ColumnsData, BytesResponse),
Result = data(ColumnsData).
try_execute_response(Stream, BytesResponse, Result) :-
empty_query_message(BytesResponse),!,
Result = [],
get_bytes(Stream, BytesEnd),
ready_for_query_message(BytesEnd).
try_execute_response(Stream, BytesResponse, Result) :-
error_message(Error, BytesResponse),!,
Result = error(Error),
get_bytes(Stream, BytesEnd),
ready_for_query_message(BytesEnd).
ext_get_data_rows(Stream, [], BytesData) :-
command_complete_message(BytesData),!,
sync_message(SyncBytes),
put_bytes(Stream, SyncBytes),
get_bytes(Stream, BytesData0),
ready_for_query_message(BytesData0).
ext_get_data_rows(Stream, [Column|Columns], BytesData) :-
data_row_message(Column, BytesData),!,
get_bytes(Stream, BytesData0),
ext_get_data_rows(Stream, Columns, BytesData0).
% https://www.postgresql.org/docs/current/protocol-flow.html#id-1.10.5.7.3
get_bytes(Stream, Bytes) :-
get_byte(Stream, BType),
get_byte(Stream, B3),
get_byte(Stream, B2),
get_byte(Stream, B1),
get_byte(Stream, B0),
int32(Length, [B3, B2, B1, B0]),
RemainingBytes is Length - 4,
get_bytes(Stream, RemainingBytes, Bytes0),
append([BType, B3, B2, B1, B0], Bytes0, Bytes),
!.
get_bytes(_, 0, []).
get_bytes(Stream, RemainingBytes, [B|Bytes]) :-
get_byte(Stream, B),
RemainingBytes1 is RemainingBytes - 1,
get_bytes(Stream, RemainingBytes1, Bytes).
put_bytes(_, []).
put_bytes(Stream, [Byte|Bytes]) :-
put_byte(Stream, Byte),
put_bytes(Stream, Bytes),
!.
sql(Connection, Query, Result) :-
sql_query(Query, TextQuery, Vars),
keysort(Vars, SortedVars),
maplist(pair_value, SortedVars, QueryVars),
query(Connection, TextQuery, QueryVars, Result).
pair_value(_-B, B).