dgraph-io / badger / 3396

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<a href="https://github.com/dgraph-io/badger/commit/<a class=hub.com/dgraph-io/badger/commit/969a8e86294e164180aabd630313a06b97827081">969a8e862<a href="https://github.com/dgraph-io/badger/commit/969a8e86294e164180aabd630313a06b97827081">&quot;&gt;Fix windows dataloss issue (#1134)

Windows doesn&amp;#39;t allow memory mapping a file to a size greater than the
file&amp;#39;s actual size. To circumvent this, we increase the file size by
truncating it.
https://github.com/dgraph-io/badger/blob/&lt;/a&gt;&lt;a class=&quot;double-link&quot; href=&quot;https://github.com/dgraph-io/badger/commit/&lt;a class=&quot;double-link&quot; href=&quot;https://git">&lt;a class=</a>hub.com/dgraph-io/badger/commit/<a class=hub.com/dgraph-io/badger/commit/f5b63211d7f3e2f5f8b698893313b2a54e4df7de">f5b63211d">f5b63211d</a><a href="https://github.com/dgraph-io/badger/commit/969a8e86294e164180aabd630313a06b97827081">/y/mmap_windows.go#L41-L48

When badger would re-open, we try to replay this &quot;truncated&quot; file.
Since this truncated file consists of all zeros, the replay would
return the last offset as `zero` and then we would truncate the
original file to size `zero`.

The replay function would return `zero` as the last valid offset
which was wrong. The last valid offset is start offset plus the
forward movements of the file offset.
So instead of
https://github.com/dgraph-io/badger/blob/f5b63211d7f3e2f5f8b698893313b2a54e4df7de/value.go#L433
```go
var validEndOff uint32 // notice we&#39;re starting from zero, not the start point.
```
we should be doing
```go
var validEndOff uint32 = offset
```
Fixes - https://github.com/dgraph-io/badger/issues/1126</a>

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