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db: fix iterator error propagation, NextPrefix violation #3593

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merged 2 commits into from
May 7, 2024
Merged

db: fix iterator error propagation, NextPrefix violation #3593

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78953f4
db: fix iterator error propagation, NextPrefix violation
jbowens May 6, 2024
925a3db
db: fix ingested flushable range deletion iterator
jbowens May 7, 2024
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64 changes: 49 additions & 15 deletions iterator.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1631,7 +1631,7 @@ func (i *Iterator) First() bool {
i.requiresReposition = false
i.stats.ForwardSeekCount[InterfaceCall]++

i.iterFirstWithinBounds()
i.err = i.iterFirstWithinBounds()
if i.err != nil {
i.iterValidityState = IterExhausted
return false
Expand Down Expand Up @@ -1667,8 +1667,7 @@ func (i *Iterator) Last() bool {
i.requiresReposition = false
i.stats.ReverseSeekCount[InterfaceCall]++

i.iterLastWithinBounds()
if i.err != nil {
if i.err = i.iterLastWithinBounds(); i.err != nil {
i.iterValidityState = IterExhausted
return false
}
Expand Down Expand Up @@ -1741,6 +1740,11 @@ func (i *Iterator) nextPrefix() IterValidityState {
// key.
i.rangeKey.updated = i.rangeKey.hasRangeKey && !i.Valid() && i.opts.rangeKeys()
}
// NextPrefix from an exhausted position is undefined. We keep the exhausted
// position, which provides determinism for the metamorphic tests.
if i.iterValidityState == IterExhausted {
return i.iterValidityState
}

// Although NextPrefix documents that behavior at IterAtLimit is undefined,
// this function handles these cases as a simple prefix-agnostic Next. This
Expand Down Expand Up @@ -1770,7 +1774,10 @@ func (i *Iterator) nextPrefix() IterValidityState {
}
// The Iterator is exhausted and i.iter is positioned before the first
// key. Reposition to point to the first internal key.
i.iterFirstWithinBounds()
if i.err = i.iterFirstWithinBounds(); i.err != nil {
i.iterValidityState = IterExhausted
return i.iterValidityState
}
case iterPosCurReversePaused:
// Positioned at a limit. Implement as a prefix-agnostic Next. See TODO
// up above.
Expand All @@ -1789,7 +1796,15 @@ func (i *Iterator) nextPrefix() IterValidityState {
if i.iterKV == nil {
// We're positioned before the first key. Need to reposition to point to
// the first key.
i.iterFirstWithinBounds()
i.err = i.iterFirstWithinBounds()
if i.iterKV == nil {
i.iterValidityState = IterExhausted
return i.iterValidityState
}
if invariants.Enabled && !i.equal(i.iterKV.K.UserKey, i.key) {
i.opts.getLogger().Fatalf("pebble: invariant violation: First internal iterator from iterPosPrev landed on %q, not %q",
i.iterKV.K.UserKey, i.key)
}
} else {
// Move the internal iterator back onto the user key stored in
// i.key. iterPosPrev guarantees that it's positioned at the last
Expand All @@ -1800,14 +1815,14 @@ func (i *Iterator) nextPrefix() IterValidityState {
// This should only be possible if i.iter.Next() encountered an
// error.
if i.iter.Error() == nil {
i.opts.logger.Fatalf("pebble: invariant violation: Nexting internal iterator from iterPosPrev found nothing")
i.opts.getLogger().Fatalf("pebble: invariant violation: Nexting internal iterator from iterPosPrev found nothing")
}
// NB: Iterator.Error() will return i.iter.Error().
i.iterValidityState = IterExhausted
return i.iterValidityState
}
if invariants.Enabled && !i.equal(i.iterKV.K.UserKey, i.key) {
i.opts.logger.Fatalf("pebble: invariant violation: Nexting internal iterator from iterPosPrev landed on %q, not %q",
i.opts.getLogger().Fatalf("pebble: invariant violation: Nexting internal iterator from iterPosPrev landed on %q, not %q",
i.iterKV.K.UserKey, i.key)
}
}
Expand Down Expand Up @@ -1850,6 +1865,10 @@ func (i *Iterator) internalNextPrefix(currKeyPrefixLen int) {
}
i.stats.ForwardStepCount[InternalIterCall]++
i.prefixOrFullSeekKey = i.comparer.ImmediateSuccessor(i.prefixOrFullSeekKey[:0], i.key[:currKeyPrefixLen])
if i.iterKV.K.IsExclusiveSentinel() {
panic(errors.AssertionFailedf("pebble: unexpected exclusive sentinel key: %q", i.iterKV.K))
}

i.iterKV = i.iter.NextPrefix(i.prefixOrFullSeekKey)
if invariants.Enabled && i.iterKV != nil {
if iterKeyPrefixLen := i.split(i.iterKV.K.UserKey); i.cmp(i.iterKV.K.UserKey[:iterKeyPrefixLen], i.prefixOrFullSeekKey) < 0 {
Expand Down Expand Up @@ -1913,7 +1932,10 @@ func (i *Iterator) nextWithLimit(limit []byte) IterValidityState {
}
// We're positioned before the first key. Need to reposition to point to
// the first key.
i.iterFirstWithinBounds()
if i.err = i.iterFirstWithinBounds(); i.err != nil {
i.iterValidityState = IterExhausted
return i.iterValidityState
}
case iterPosCurReversePaused:
// Switching directions.
// The iterator must not be exhausted since it paused.
Expand All @@ -1933,10 +1955,14 @@ func (i *Iterator) nextWithLimit(limit []byte) IterValidityState {
if i.iterKV == nil {
// We're positioned before the first key. Need to reposition to point to
// the first key.
i.iterFirstWithinBounds()
i.err = i.iterFirstWithinBounds()
} else {
i.nextUserKey()
}
if i.err != nil {
i.iterValidityState = IterExhausted
return i.iterValidityState
}
i.nextUserKey()
case iterPosNext:
// Already at the right place.
Expand Down Expand Up @@ -2031,12 +2057,12 @@ func (i *Iterator) PrevWithLimit(limit []byte) IterValidityState {
if i.iterKV == nil {
// We're positioned after the last key. Need to reposition to point to
// the last key.
i.iterLastWithinBounds()
i.err = i.iterLastWithinBounds()
} else {
i.prevUserKey()
if i.err != nil {
return i.iterValidityState
}
}
if i.err != nil {
return i.iterValidityState
}
if stepAgain {
i.prevUserKey()
Expand All @@ -2052,24 +2078,32 @@ func (i *Iterator) PrevWithLimit(limit []byte) IterValidityState {

// iterFirstWithinBounds moves the internal iterator to the first key,
// respecting bounds.
func (i *Iterator) iterFirstWithinBounds() {
func (i *Iterator) iterFirstWithinBounds() error {
i.stats.ForwardSeekCount[InternalIterCall]++
if lowerBound := i.opts.GetLowerBound(); lowerBound != nil {
i.iterKV = i.iter.SeekGE(lowerBound, base.SeekGEFlagsNone)
} else {
i.iterKV = i.iter.First()
}
if i.iterKV == nil {
return i.iter.Error()
}
return nil
}

// iterLastWithinBounds moves the internal iterator to the last key, respecting
// bounds.
func (i *Iterator) iterLastWithinBounds() {
func (i *Iterator) iterLastWithinBounds() error {
i.stats.ReverseSeekCount[InternalIterCall]++
if upperBound := i.opts.GetUpperBound(); upperBound != nil {
i.iterKV = i.iter.SeekLT(upperBound, base.SeekLTFlagsNone)
} else {
i.iterKV = i.iter.Last()
}
if i.iterKV == nil {
return i.iter.Error()
}
return nil
}

// RangeKeyData describes a range key's data, set through RangeKeySet. The key
Expand Down
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