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fix(pebble.go): implement flush threshold for Pebble batch operations #275

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fix(pebble.go): implement flush threshold for Pebble batch operations #275

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17 changes: 17 additions & 0 deletions pebble.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ type PebbleDB struct {
}

var _ DB = (*PebbleDB)(nil)
const flushThreshold = 3_500_000_000 // ~3.5 GB

func NewPebbleDB(name string, dir string) (*PebbleDB, error) {
opts := &pebble.Options{}
Expand Down Expand Up @@ -250,6 +251,14 @@ func (b *pebbleDBBatch) Set(key, value []byte) error {
return errBatchClosed
}

// Prevent Pebble batch from exceeding 4 GB hard limit
if b.batch.Len() > flushThreshold {
if err := b.batch.Commit(pebble.Sync); err != nil {
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@cursor cursor bot Oct 23, 2025

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Bug: Batch Flush Sync Inconsistency

The automatic batch flush uses pebble.Sync, which is inconsistent with the pebble.NoSync used by the Write() method. This introduces unexpected synchronous writes during batch building, potentially causing performance slowdowns and violating user expectations.

Fix in Cursor Fix in Web

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@StrathCole StrathCole Oct 23, 2025

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I would think this is necessary due to the location the commit is called, as it "interrupts" a normal batch operation, this should not simply continue until the batch is committed.

return err
}
b.batch.Reset()
}

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Bug: Batch Size Check Timing Issue

The batch size check in pebbleDBBatch.Set and Delete happens before adding the operation. This means a large operation can push the batch over Pebble's 4GB hard limit, even if the current size is below the flushThreshold.

Additional Locations (1)

Fix in Cursor Fix in Web

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@StrathCole StrathCole Oct 23, 2025

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In my opinion this would be unlikely to happen. Single operations normally are much smaller, just batching them can lead to the issue.

return b.batch.Set(key, value, nil)
}

Expand All @@ -262,6 +271,14 @@ func (b *pebbleDBBatch) Delete(key []byte) error {
return errBatchClosed
}

// Prevent Pebble batch from exceeding 4 GB hard limit
if b.batch.Len() > flushThreshold {
if err := b.batch.Commit(pebble.Sync); err != nil {
return err
}
b.batch.Reset()
}

return b.batch.Delete(key, nil)
}

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