GameCult/CultLib
Watch
9
0
Fork
You've already forked CultLib
 0
Code Issues Pull requests 1 Projects Releases Packages Wiki Activity Actions

C# write set: a record written over another is stored later than the one it replaces

Browse source 
ApplyWriteSet re-mints an upsert's storedAt when the durable record it replaces is not
earlier, so A-B-A on the same wall clock cannot read as unchanged. Two stale whole-view
comments are corrected.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
This commit is contained in:
Meta Vens 2026-10-03 05:04:37 +02:00
commit ebd66e6f5b
1 changed files with 15 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

17
src/GameCult.Caching/CultCache.cs
View file

@ -504,7 +504,7 @@ namespace GameCult.Caching
public CultRecordKey Key { get; }
// When the record was stored. With StoredSchemaId it names the record's stored bytes: a write that stores the record
// differently mints it again, including a whole-view write that re-encodes it.
// mints it a storedAt later than the one it replaces.
public string StoredAt { get; internal set; }
public CultDocumentDescriptor Descriptor { get; }
@ -1867,7 +1867,7 @@ namespace GameCult.Caching
// durable is what the store holds on disk now; observed is what its cache last loaded or committed.
// Identity is (stored schema id, storedAt), compared exactly. It names the stored bytes: every write that stores a record
// differently mints it a later storedAt, including a whole-view write that re-encodes a record it loaded.
// mints it a storedAt later than the one it replaces.
public bool ConditionsHold(IReadOnlyCollection<CultPersistedRecord> durable, IEnumerable<CultStoredDocument> observed)
{
var byKey = durable.ToDictionary(record => record.Key, StringComparer.Ordinal);
@ -3920,6 +3920,14 @@ namespace GameCult.Caching
private IReadOnlyCollection<CultStagedRecord> ApplyWriteSet(CultPersistedStoreSnapshot? durable, IReadOnlyCollection<CultStagedRecord> upserts, IReadOnlyCollection<string> removals)
{
RefuseWriteIntoMovedVariantStore(durable, upserts, removals);
// A record written over one the store holds is stored at a storedAt later than the one it replaces, whoever wrote that.
var replaced = (durable?.Records ?? Array.Empty<CultPersistedRecord>()).ToDictionary(record => record.Key, record => record.StoredAt, StringComparer.Ordinal);
foreach (var staged in upserts)
{
if (replaced.TryGetValue(staged.Record.Key, out var durableAt) && !StoredLater(staged.Record.StoredAt, durableAt))
staged.Record.StoredAt = MintStoredAt(durableAt);
}
var written = upserts.Select(staged => staged.Record.Key).ToHashSet(StringComparer.Ordinal);
var removed = removals.ToHashSet(StringComparer.Ordinal);
var copied = (durable?.Records ?? Array.Empty<CultPersistedRecord>())
@ -3955,6 +3963,11 @@ namespace GameCult.Caching
return upserts;
}
private static bool StoredLater(string storedAt, string than) =>
DateTimeOffset.TryParse(storedAt, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out var later) &&
DateTimeOffset.TryParse(than, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out var earlier) &&
later > earlier;
private void RefuseWriteIntoMovedVariantStore(CultPersistedStoreSnapshot? durable, IReadOnlyCollection<CultStagedRecord> upserts, IReadOnlyCollection<string> removals)
{
var records = durable?.Records ?? Array.Empty<CultPersistedRecord>();