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Ranges cache: add ownership check #6004

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merged 2 commits into from
Jun 4, 2023
Merged

Ranges cache: add ownership check #6004

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6dfb0a8
add ownership check. if the value isn't owned, copy it
Jonathan-Rosenberg Jun 1, 2023
17e20a2
stop copying value's bytes since the byte buffer is owned by the call…
Jonathan-Rosenberg Jun 4, 2023
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3 changes: 1 addition & 2 deletions pkg/graveler/committed/value.go
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Original file line number Diff line number Diff line change
Expand Up @@ -74,8 +74,7 @@ func getBytes(b *[]byte) ([]byte, error) {
if l < 0 {
return nil, fmt.Errorf("impossible negative length %d: %w", l, ErrBadValueBytes)
}
ret := make([]byte, l)
copy(ret, (*b)[:l])
ret := (*b)[:l]
*b = (*b)[l:]
return ret, nil
}
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16 changes: 14 additions & 2 deletions pkg/graveler/sstable/range_manager.go
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Original file line number Diff line number Diff line change
Expand Up @@ -92,7 +92,13 @@ func (m *RangeManager) GetValueGE(ctx context.Context, ns committed.Namespace, i
}
return nil, ErrKeyNotFound
}
vBytes, _, err := value.Value(nil)
vBytes, owned, err := value.Value(nil)
if !owned {
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Wow, great catch!

Is there any way for us to change this bad ownership status? IIUC when !owned, iterator it shares underlying state with some other iterator. I would expect this state to persist, and now very many calls (including future getValue()s) will keep on copying every value. It might be considerably more efficient if we could convince Pebble to unshare the iterator -- say by creating future iterators on a new iterator hierarchy. (It goes without saying that this is no reason to delay this PR!)

b := vBytes
vBytes = make([]byte, len(b))
copy(vBytes, b)
}

if err != nil {
return nil, fmt.Errorf("extract value from sstable id %s (key %s): %w", id, key, err)
}
Expand Down Expand Up @@ -132,7 +138,13 @@ func (m *RangeManager) GetValue(ctx context.Context, ns committed.Namespace, id
// lookup path in range but key not found
return nil, ErrKeyNotFound
}
vBytes, _, err := value.Value(nil)
vBytes, owned, err := value.Value(nil)
if !owned {
b := vBytes
vBytes = make([]byte, len(b))
copy(vBytes, b)
}

if err != nil {
return nil, fmt.Errorf("extract value from sstable id %s (key %s): %w", id, key, err)
}
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