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Merged
tsloughter merged 5 commits into from
Apr 7, 2025
Merged

Support UTC offset in pg_timestampz::encode/2 #10

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330d9a2
Add UTC offset to timestampz encoder
tsloughter Nov 12, 2024
ee0a639
Update type_spec to reflect possible inputs
chiroptical Mar 31, 2025
548904a
Minute offset must be positive
chiroptical Mar 31, 2025
2f1f617
Add unit tests and fix offset bug
chiroptical Apr 2, 2025
6445cd9
Add some documentation pointing the unit tests for examples
chiroptical Apr 2, 2025
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3 changes: 3 additions & 0 deletions .github/workflows/ci.yml
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Expand Up @@ -37,6 +37,9 @@ jobs:
- name: Compile
run: rebar3 compile

- name: Eunit tests
run: rebar3 eunit
Comment on lines +40 to +41
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@chiroptical chiroptical Apr 2, 2025

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I added basic unit tests to make the offset code more obvious


- name: Proper tests
run: rebar3 as test proper

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25 changes: 25 additions & 0 deletions src/pg_timestamp.erl
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Expand Up @@ -49,9 +49,27 @@ encode_timestamp(infinity) ->
16#7FFFFFFFFFFFFFFF;
encode_timestamp('-infinity') ->
-16#8000000000000000;
% A timestamp with a positive offset is a time in the future, compared to UTC,
% and therefore you need to subtract the hour and minutes to generate a UTC
% time. Please see 'test/timestamptz_tests.erl' for some examples.
encode_timestamp({{Year, Month, Day}, {Hour, Minute, Seconds}, {HourOffset, MinuteOffset}}) when is_integer(Seconds), MinuteOffset >= 0 ->
Sign = determine_sign(HourOffset),
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@chiroptical chiroptical Jan 5, 2025

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The offset is either positive or negative. calendar:time_to_seconds doesn't work with negative values though.

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@chiroptical chiroptical Mar 31, 2025

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I think this is just wrong?

1> calendar:time_to_seconds({0, -100, 0}).
-6000
2> calendar:time_to_seconds({-10, 100, 0}).
-30000
3> calendar:time_to_seconds({-10, 0, 0}).
-36000
4> calendar:time_to_seconds({-100, 0, 0}).
-360000

OffsetFromHours = calendar:time_to_seconds({abs(HourOffset), 0, 0}),
OffsetFromMinutes = calendar:time_to_seconds({0, MinuteOffset, 0}),
DatetimeSeconds = calendar:datetime_to_gregorian_seconds({{Year, Month, Day}, {Hour, Minute, Seconds}}) - ?POSTGRESQL_GS_EPOCH,
(DatetimeSeconds + OffsetFromHours * Sign + OffsetFromMinutes * Sign) * 1000000;
encode_timestamp(Datetime={{_, _, _}, {_, _, Seconds}}) when is_integer(Seconds)->
Secs = calendar:datetime_to_gregorian_seconds(Datetime) - ?POSTGRESQL_GS_EPOCH,
Secs * 1000000;
encode_timestamp({{Year, Month, Day}, {Hours, Minutes, Seconds}, {HourOffset, MinuteOffset}}) when is_float(Seconds), MinuteOffset >= 0 ->
Sign = determine_sign(HourOffset),
OffsetFromHours = calendar:time_to_seconds({abs(HourOffset), 0, 0}),
OffsetFromMinutes = calendar:time_to_seconds({0, MinuteOffset, 0}),
IntegerSeconds = trunc(Seconds),
US = trunc((Seconds - IntegerSeconds) * 1000000),
DatetimeSeconds = calendar:datetime_to_gregorian_seconds({{Year, Month, Day},
{Hours, Minutes, IntegerSeconds}}) - ?POSTGRESQL_GS_EPOCH,
((DatetimeSeconds + OffsetFromHours * Sign + OffsetFromMinutes * Sign) * 1000000) + US;
encode_timestamp({{Year, Month, Day}, {Hours, Minutes, Seconds}}) when is_float(Seconds)->
IntegerSeconds = trunc(Seconds),
US = trunc((Seconds - IntegerSeconds) * 1000000),
Expand Down Expand Up @@ -88,3 +106,10 @@ add_usecs(Secs, 0) ->
Secs;
add_usecs(Secs, USecs) ->
Secs + (USecs / 1000000).

% When the hour offset is positive, you are in the future and therefore
% need to subtract the hours to get to UTC.
determine_sign(HourOffset) when HourOffset >= 0 ->
-1;
determine_sign(_) ->
1.
2 changes: 1 addition & 1 deletion src/pg_timestampz.erl
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Expand Up @@ -19,4 +19,4 @@ decode(Bin, _TypeInfo) ->
pg_timestamp:decode_timestamp(Bin, []).

type_spec() ->
pg_timestamp:type_spec().
"{{Year::integer(), Month::1..12, Day::1..31}, {Hours::integer(), Minutes::integer(), Seconds::integer() | float()}, {HourOffset::integer(), MinuteOffset::pos_integer()}}".
17 changes: 17 additions & 0 deletions test/prop_timestamp.erl
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Expand Up @@ -9,5 +9,22 @@ prop_tz_int_sec_codec() ->
?FORALL(Val, int_timestamp(),
proper_lib:codec(pg_timestampz, [], Val)).

prop_tz_offset_codec() ->
?FORALL(Val, utc_offset_timestamp(),
proper_lib:codec(pg_timestampz, [], Val, apply_offset(Val))).

apply_offset({{Year, Month, Day}, {Hour, Minute, Second}, {HourOffset, MinuteOffset}}) ->
Sign = case HourOffset >= 0 of
true -> -1;
false -> 1
end,
OffsetHours = calendar:time_to_seconds({abs(HourOffset), 0, 0}),
OffsetMinutes = calendar:time_to_seconds({0, MinuteOffset, 0}),
DatetimeSeconds = calendar:datetime_to_gregorian_seconds({{Year, Month, Day}, {Hour, Minute, Second}}),
calendar:gregorian_seconds_to_datetime(DatetimeSeconds + OffsetHours * Sign + OffsetMinutes * Sign).

int_timestamp() ->
{proper_lib:date_gen(), proper_lib:int_time_gen()}.

utc_offset_timestamp() ->
{proper_lib:date_gen(), proper_lib:int_time_gen(), proper_lib:utc_offset_gen()}.
26 changes: 21 additions & 5 deletions test/proper_lib.erl
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@@ -1,9 +1,9 @@
-module(proper_lib).

-export([codec/3, codec/4]).
-export([codec/3, codec/4, encode_decode/3]).

-export([int16/0, int32/0, int64/0,
date_gen/0, int_time_gen/0]).
date_gen/0, int_time_gen/0, utc_offset_gen/0]).

-include_lib("proper/include/proper.hrl").
-include_lib("stdlib/include/assert.hrl").
Expand All @@ -12,11 +12,23 @@
codec(Mod, Opts, Data) ->
codec(Mod, Opts, Data, fun(V) -> V end).

codec(Mod, Opts, Data, Canonical) ->
% Encode and then decode the Input
encode_decode(Mod, Opts, Input) ->
{_, Config} = Mod:init(Opts),
TypeInfo = #type_info{config = Config},
<<Size:32, Encoded:Size/binary>> = iolist_to_binary(Mod:encode(Data, TypeInfo)),
Canonical(Data) =:= Canonical(Mod:decode(Encoded, TypeInfo)).
<<Size:32, Encoded:Size/binary>> = iolist_to_binary(Mod:encode(Input, TypeInfo)),
Mod:decode(Encoded, TypeInfo).
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@chiroptical chiroptical Apr 2, 2025

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I found the unit tests more readable with ?assertEqual and therefore it is useful to simply have the value back after encoding and then decoding.


% Passing a function will apply that function to the input Data and
% encoded/decoded Data before comparison.
codec(Mod, Opts, Data, Canonical) when is_function(Canonical) ->
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@chiroptical chiroptical Apr 2, 2025

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This is the original codec function

Decoded = encode_decode(Mod, Opts, Data),
Canonical(Data) =:= Canonical(Decoded);
% Passing anything else will simply compare the Output with the encoded/decoded
% Input
codec(Mod, Opts, Data, Output) ->
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@chiroptical chiroptical Apr 2, 2025

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This version is more convenient in the property test. Without this, I need a more complicated function to deal with the round-trip. Something like,

f({{_X, _Y, _Z}, {_A, _B, _C}, {_D, _E}} = Timestamp) -> apply_offset(Timestamp);
f({{_X, _Y, _Z}, {_A, _B, _C} = Timestamp} -> Timestamp.

It isn't that complicated, but it is much easier to just provide the expected output.

Decoded = encode_decode(Mod, Opts, Data),
Output =:= Decoded.

%%
%% Generators
Expand All @@ -39,6 +51,10 @@ date_gen() ->
proper_types:integer(1, 31)},
calendar:valid_date(Date)).

utc_offset_gen() ->
{proper_types:integer(-15, 15),
proper_types:integer(0, 59)}.
Comment on lines +54 to +56
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@chiroptical chiroptical Jan 15, 2025

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I just tested various values in psql until they failed.


int_time_gen() ->
{proper_types:integer(0, 23),
proper_types:integer(0, 59),
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33 changes: 33 additions & 0 deletions test/timestamptz_tests.erl
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@@ -0,0 +1,33 @@
-module(timestamptz_tests).

-include_lib("eunit/include/eunit.hrl").

negative_offset_timestamptz_test() ->
?assertEqual(
proper_lib:encode_decode(
pg_timestampz,
[],
{{2024, 3, 1}, {1, 0, 0}, {-5, 15}}
),
{{2024, 3, 1}, {6, 15, 0}}
).

positive_offset_timestamptz_test() ->
?assertEqual(
proper_lib:encode_decode(
pg_timestampz,
[],
{{2024, 3, 1}, {1, 0, 0}, {5, 15}}
),
{{2024, 2, 29}, {19, 45, 0}}
).

no_offset_timestamptz_test() ->
?assertEqual(
proper_lib:encode_decode(
pg_timestampz,
[],
{{2024, 3, 1}, {1, 0, 0}, {0, 0}}
),
{{2024, 3, 1}, {1, 0, 0}}
).
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