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perf(charts): code-unit ISO date scan in ChartData.parseTime (#1514) #1604

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Merged
ZhuchkaTriplesix merged 1 commit into from
Oct 15, 2026
Merged

perf(charts): code-unit ISO date scan in ChartData.parseTime (#1514) #1604

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95 changes: 83 additions & 12 deletions lib/features/results/charts/chart_data.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -45,32 +45,103 @@ class ChartData {
/// Name of the slice that collects the categories beyond Top N.
static const String otherLabel = 'Other';

static final _isoTime = RegExp(
r'^\d{4}-\d{2}-\d{2}([T ]\d{2}:\d{2}(:\d{2}(\.\d+)?)?)?(Z|[+-]\d{2}:?\d{2})?$',
);
static final _hasZone = RegExp(r'(Z|[+-]\d{2}:?\d{2})$');
static bool _digitsAt(String s, int at, int count) {
if (at + count > s.length) return false;
for (var i = at; i < at + count; i++) {
final c = s.codeUnitAt(i);
if (c < 0x30 || c > 0x39) return false;
}
return true;
}

/// The decimal value of the [count] digits at [at], or -1 when they are not
/// all digits.
static int _digitsValue(String s, int at, int count) {
if (!_digitsAt(s, at, count)) return -1;
var v = 0;
for (var i = at; i < at + count; i++) {
v = v * 10 + (s.codeUnitAt(i) - 0x30);
}
return v;
}

/// Checks [s] against
/// `YYYY-MM-DD([T ]HH:MM(:SS(.f+)?)?)?(Z|[+-]HH:?MM)?` without a regex:
/// -1 when it does not fit, 1 when it ends in a zone, 0 otherwise.
static int _scanIso(String s) {
final n = s.length;
if (n < 10 ||
!_digitsAt(s, 0, 4) ||
s.codeUnitAt(4) != 0x2D ||
!_digitsAt(s, 5, 2) ||
s.codeUnitAt(7) != 0x2D ||
!_digitsAt(s, 8, 2)) {
return -1;
}
var i = 10;
if (i < n) {
final sep = s.codeUnitAt(i);
if (sep == 0x54 || sep == 0x20) {
// [T ]HH:MM
if (!_digitsAt(s, i + 1, 2) ||
i + 3 >= n ||
s.codeUnitAt(i + 3) != 0x3A ||
!_digitsAt(s, i + 4, 2)) {
return -1;
}
i += 6;
// :SS
if (i < n && s.codeUnitAt(i) == 0x3A && _digitsAt(s, i + 1, 2)) {
i += 3;
// .f+
if (i < n && s.codeUnitAt(i) == 0x2E && _digitsAt(s, i + 1, 1)) {
i++;
while (i < n && _digitsAt(s, i, 1)) {
i++;
}
}
}
}
}
if (i == n) return 0;
final z = s.codeUnitAt(i);
if (z == 0x5A) return i + 1 == n ? 1 : -1; // Z
if (z != 0x2B && z != 0x2D) return -1; // + or -
i++;
if (!_digitsAt(s, i, 2)) return -1;
i += 2;
if (i < n && s.codeUnitAt(i) == 0x3A) i++;
if (!_digitsAt(s, i, 2)) return -1;
return i + 2 == n ? 1 : -1;
}

/// Parses an ISO date (`2026-01-31`) or timestamp (`2026-01-31 10:00`,
/// `2026-01-31T10:00:00Z`). Without a zone the wall-clock fields are kept, so
/// a day stays a day whatever the machine's time zone is.
///
/// Called for every cell of a candidate X column (up to 100,000 rows), so the
/// shape check and the field read-back work on code units: no regex, no
/// substring, no `replaceFirst` (#1514).
static DateTime? parseTime(String raw) {
final text = raw.trim();
if (!_isoTime.hasMatch(text)) return null;
final parsed = DateTime.tryParse(text.replaceFirst(' ', 'T'));
final zone = _scanIso(text);
if (zone < 0) return null;
// DateTime.tryParse takes a space as well as `T` between date and time.
final parsed = DateTime.tryParse(text);
if (parsed == null) return null;
// DateTime rolls an impossible date over (2026-13-45 becomes 2027-02-14);
// the fields must read back as typed.
if (parsed.year != int.parse(text.substring(0, 4)) ||
parsed.month != int.parse(text.substring(5, 7)) ||
parsed.day != int.parse(text.substring(8, 10))) {
if (parsed.year != _digitsValue(text, 0, 4) ||
parsed.month != _digitsValue(text, 5, 2) ||
parsed.day != _digitsValue(text, 8, 2)) {
return null;
}
if (text.length >= 16 &&
(parsed.hour != int.parse(text.substring(11, 13)) ||
parsed.minute != int.parse(text.substring(14, 16)))) {
(parsed.hour != _digitsValue(text, 11, 2) ||
parsed.minute != _digitsValue(text, 14, 2))) {
return null;
}
if (_hasZone.hasMatch(text)) return parsed.toUtc();
if (zone == 1) return parsed.toUtc();
return DateTime.utc(parsed.year, parsed.month, parsed.day, parsed.hour,
parsed.minute, parsed.second, parsed.millisecond, parsed.microsecond);
}
Expand Down
123 changes: 123 additions & 0 deletions test/features/results/charts/chart_data_parse_time_test.dart
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Original file line number Diff line number Diff line change
@@ -0,0 +1,123 @@
import 'dart:math';

import 'package:flutter_test/flutter_test.dart';
import 'package:querya_desktop/features/results/charts/chart_data.dart';

/// `ChartData.parseTime` before #1514 (regex, replaceFirst, substrings): the
/// reference the code-unit version has to agree with.
final _isoTime = RegExp(
r'^\d{4}-\d{2}-\d{2}([T ]\d{2}:\d{2}(:\d{2}(\.\d+)?)?)?(Z|[+-]\d{2}:?\d{2})?$',
);
final _hasZone = RegExp(r'(Z|[+-]\d{2}:?\d{2})$');

DateTime? _reference(String raw) {
final text = raw.trim();
if (!_isoTime.hasMatch(text)) return null;
final parsed = DateTime.tryParse(text.replaceFirst(' ', 'T'));
if (parsed == null) return null;
if (parsed.year != int.parse(text.substring(0, 4)) ||
parsed.month != int.parse(text.substring(5, 7)) ||
parsed.day != int.parse(text.substring(8, 10))) {
return null;
}
if (text.length >= 16 &&
(parsed.hour != int.parse(text.substring(11, 13)) ||
parsed.minute != int.parse(text.substring(14, 16)))) {
return null;
}
if (_hasZone.hasMatch(text)) return parsed.toUtc();
return DateTime.utc(parsed.year, parsed.month, parsed.day, parsed.hour,
parsed.minute, parsed.second, parsed.millisecond, parsed.microsecond);
}

void main() {
group('ChartData.parseTime scanner (#1514)', () {
test('agrees with the previous implementation on listed values', () {
const cases = <String>[
'',
' ',
'2026-01-31',
' 2026-01-31 ',
'2026-01-31 10:30',
'2026-01-31T10:30',
'2026-01-31T10:30:15',
'2026-01-31T10:30:15.123',
'2026-01-31T10:30:15.123456',
'2026-01-31T10:30:15.',
'2026-01-31T10:30:1',
'2026-01-31T10:3',
'2026-01-31T10',
'2026-01-31T10:30Z',
'2026-01-31T10:30:00Z',
'2026-01-31 10:30:00+02:00',
'2026-01-31 10:30:00-0530',
'2026-01-31 10:30:00+02',
'2026-01-31 10:30:00 +02:00',
'2026-01-31Z',
'2026-01-31+01:00',
'2026-01-31+0100',
'2026-13-45',
'2026-02-30',
'2026-02-29',
'2024-02-29',
'2026-01-31T25:00',
'2026-01-31T10:61',
'2026-01-31T24:00',
'2026-1-31',
'26-01-31',
'31.01.2026',
'2026/01/31',
'2026-01-31x',
'2026-01-31T10:30:00zZ',
'2026-01-31t10:30',
'2026-01-31 10:30',
'0000-01-01',
'9999-12-31T23:59:59.999Z',
'２０２６-01-31',
];
for (final raw in cases) {
expect(ChartData.parseTime(raw), _reference(raw), reason: '"$raw"');
}
});

test('agrees with the previous implementation on random strings', () {
const pieces = <String>[
'2026', '2024', '0000', '99', '01', '12', '13', '31', '45', '10', '24',
'60', '-', ':', '.', ' ', 'T', 'Z', '+', 'z', 't', '5', 'x',
];
final random = Random(1514);
for (var n = 0; n < 6000; n++) {
// Mostly shaped like a date, with random pieces dropped and swapped in.
final parts = <String>[
'2026', '-', '01', '-', '31',
if (random.nextBool()) ...[
random.nextBool() ? 'T' : ' ',
'10', ':', '30',
if (random.nextBool()) ...[':', '15'],
if (random.nextBool()) ...['.', '123'],
],
if (random.nextBool()) ...[
random.nextBool() ? 'Z' : '+',
'02', if (random.nextBool()) ':', '00',
],
];
for (var k = random.nextInt(3); k > 0; k--) {
parts[random.nextInt(parts.length)] =
pieces[random.nextInt(pieces.length)];
}
final raw = parts.join();
expect(ChartData.parseTime(raw), _reference(raw), reason: '"$raw"');
}
});

test('a 100,000 row column is checked in one pass', () {
final rows = [
for (var i = 0; i < 100000; i++)
['2026-01-${(i % 28 + 1).toString().padLeft(2, '0')} 10:30:00'],
];
expect(ChartData.isTimeColumn(rows, 0), isTrue);
rows.add(['not a date']);
expect(ChartData.isTimeColumn(rows, 0), isFalse);
});
});
}
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