internal/keyspan: clean up InterleavingIter

Remove superfluous Split parameter. Split was required for implementing
masking, but a direct implementation of masking was replaced with generic
Hooks.

Also, don't interleave a synthetic marker for empty spans. The synthetic marker
doesn't serve any purpose if there are no keys defined over the span. This
allows us to return a synthetic marker using an arbitrary Key's kind (rather
than always using RANGEKEYSET, even if the Span contained no RANGEKEYSET keys).

db.go

@@ -978,7 +978,7 @@ func finishInitializingIter(buf *iterAlloc) *Iterator {
 		// NB: The interleaving iterator is always reinitialized, even if
 		// dbi already had an initialized range key iterator, in case the point
 		// iterator changed or the range key masking suffix changed.
-		dbi.rangeKey.iter.Init(dbi.cmp, dbi.split, dbi.iter, dbi.rangeKey.rangeKeyIter, keyspan.Hooks{
+		dbi.rangeKey.iter.Init(dbi.cmp, dbi.iter, dbi.rangeKey.rangeKeyIter, keyspan.Hooks{
 			SpanChanged: dbi.rangeKeySpanChanged,
 			SkipPoint:   dbi.rangeKeySkipPoint,
 		})

external_iterator.go

@@ -143,7 +143,7 @@ func NewExternalIter(
 			rangeKeyIters...,
 		)
 
-		dbi.rangeKey.iter.Init(dbi.cmp, dbi.split, &buf.merging, dbi.rangeKey.rangeKeyIter, keyspan.Hooks{
+		dbi.rangeKey.iter.Init(dbi.cmp, &buf.merging, dbi.rangeKey.rangeKeyIter, keyspan.Hooks{
 			SpanChanged: dbi.rangeKeySpanChanged,
 			SkipPoint:   dbi.rangeKeySkipPoint,
 		})

internal/keyspan/interleaving_iter.go

@@ -85,7 +85,6 @@ type Hooks struct {
 // All spans containing keys are exposed during iteration.
 type InterleavingIter struct {
 	cmp         base.Compare
-	split       base.Split
 	pointIter   base.InternalIteratorWithStats
 	keyspanIter FragmentIterator
 	hooks       Hooks
@@ -149,14 +148,12 @@ var _ base.InternalIterator = &InterleavingIter{}
 // with key spans from keyspanIter.
 func (i *InterleavingIter) Init(
 	cmp base.Compare,
-	split base.Split,
 	pointIter base.InternalIteratorWithStats,
 	keyspanIter FragmentIterator,
 	hooks Hooks,
 ) {
 	*i = InterleavingIter{
 		cmp:         cmp,
-		split:       split,
 		pointIter:   pointIter,
 		keyspanIter: keyspanIter,
 		hooks:       hooks,
@@ -381,10 +378,12 @@ func (i *InterleavingIter) Prev() (*base.InternalKey, []byte) {
 
 func (i *InterleavingIter) interleaveForward(lowerBound []byte) (*base.InternalKey, []byte) {
 	// This loop determines whether a point key or a span marker key should be
-	// interleaved on each iteration. If masking is disabled, this loop executes
-	// for exactly one iteration. If masking is enabled and a masked key is
-	// determined to be interleaved next, this loop continues until the
-	// interleaved key is unmasked.
+	// interleaved on each iteration. If masking is disabled and the span is
+	// nonempty, this loop executes for exactly one iteration. If masking is
+	// enabled and a masked key is determined to be interleaved next, this loop
+	// continues until the interleaved key is unmasked. If a span's start key
+	// should be interleaved next, but the span is empty, the loop continues to
+	// the next key.
 	for {
 		// Check invariants.
 		// INVARIANT: !pointKeyInterleaved
@@ -425,12 +424,20 @@ func (i *InterleavingIter) interleaveForward(lowerBound []byte) (*base.InternalK
 					return i.yieldNil()
 				}
 			}
+			if i.span.Empty() {
+				i.keyspanInterleaved = true
+				continue
+			}
 			return i.yieldSyntheticSpanMarker(lowerBound)
 		default:
 			if i.cmp(i.pointKey.UserKey, i.span.Start) >= 0 {
 				// The span start key lies before the point key. If we haven't
 				// interleaved it, we should.
 				if !i.keyspanInterleaved {
+					if i.span.Empty() {
+						i.keyspanInterleaved = true
+						continue
+					}
 					return i.yieldSyntheticSpanMarker(lowerBound)
 				}
 
@@ -473,10 +480,12 @@ func (i *InterleavingIter) interleaveForward(lowerBound []byte) (*base.InternalK
 
 func (i *InterleavingIter) interleaveBackward() (*base.InternalKey, []byte) {
 	// This loop determines whether a point key or a span's start key should be
-	// interleaved on each iteration. If masking is disabled, this loop executes
-	// for exactly one iteration. If masking is enabled and a masked key is
-	// determined to be interleaved next, this loop continues until the
-	// interleaved key is unmasked.
+	// interleaved on each iteration. If masking is disabled and the span is
+	// nonempty, this loop executes for exactly one iteration. If masking is
+	// enabled and a masked key is determined to be interleaved next, this loop
+	// continues until the interleaved key is unmasked. If a span's start key
+	// should be interleaved next, but the span is empty, the loop continues to
+	// the next key.
 	for {
 		// Check invariants.
 		// INVARIANT: !pointKeyInterleaved
@@ -491,11 +500,19 @@ func (i *InterleavingIter) interleaveBackward() (*base.InternalKey, []byte) {
 			return i.yieldPointKey(false /* covered */)
 		case i.pointKey == nil:
 			// If we're out of point keys, we need to return a span marker.
+			if i.span.Empty() {
+				i.keyspanInterleaved = true
+				continue
+			}
 			return i.yieldSyntheticSpanMarker(i.lower)
 		default:
 			// If the span's start key is greater than the point key, return a
 			// marker for the span.
 			if i.cmp(i.span.Start, i.pointKey.UserKey) > 0 {
+				if i.span.Empty() {
+					i.keyspanInterleaved = true
+					continue
+				}
 				return i.yieldSyntheticSpanMarker(i.lower)
 			}
 			// We have a span but it has not been interleaved and begins at a
@@ -570,9 +587,8 @@ func (i *InterleavingIter) yieldPointKey(covered bool) (*base.InternalKey, []byt
 }
 
 func (i *InterleavingIter) yieldSyntheticSpanMarker(lowerBound []byte) (*base.InternalKey, []byte) {
-	// TODO(jackson): Elide empty spans.
 	i.spanMarker.UserKey = i.span.Start
-	i.spanMarker.Trailer = base.InternalKeyBoundaryRangeKey
+	i.spanMarker.Trailer = base.MakeTrailer(base.InternalKeySeqNumMax, i.span.Keys[0].Kind())
 	i.keyspanInterleaved = true
 	i.spanCoversKey = true
 

internal/keyspan/interleaving_iter_test.go

@@ -90,7 +90,7 @@ func runInterleavingIterTest(t *testing.T, filename string) {
 			}
 			keyspanIter.Init(cmp, noopTransform, NewIter(cmp, spans))
 			hooks.maskSuffix = nil
-			iter.Init(cmp, testkeys.Comparer.Split, base.WrapIterWithStats(&pointIter), &keyspanIter, Hooks{
+			iter.Init(cmp, base.WrapIterWithStats(&pointIter), &keyspanIter, Hooks{
 				SpanChanged: hooks.SpanChanged,
 				SkipPoint:   hooks.SkipPoint,
 			})
@@ -103,7 +103,7 @@ func runInterleavingIterTest(t *testing.T, filename string) {
 			}
 			pointIter = pointIterator{cmp: cmp, keys: points}
 			hooks.maskSuffix = nil
-			iter.Init(cmp, testkeys.Comparer.Split, base.WrapIterWithStats(&pointIter), &keyspanIter, Hooks{
+			iter.Init(cmp, base.WrapIterWithStats(&pointIter), &keyspanIter, Hooks{
 				SpanChanged: hooks.SpanChanged,
 				SkipPoint:   hooks.SkipPoint,
 			})

internal/keyspan/testdata/interleaving_iter

@@ -54,10 +54,10 @@ Span: c-d:{(#4,RANGEKEYSET,@3,coconut)}
 PointKey: e#72057594037927935,21
 Span: e-f:{(#20,RANGEKEYSET,@5,pineapple) (#20,RANGEKEYSET,@3,guava)}
 -
-PointKey: h#72057594037927935,21
+PointKey: h#72057594037927935,19
 Span: h-j:{(#22,RANGEKEYDEL) (#21,RANGEKEYSET,@5,peaches) (#21,RANGEKEYSET,@3,starfruit)}
 -
-PointKey: l#72057594037927935,21
+PointKey: l#72057594037927935,20
 Span: l-m:{(#2,RANGEKEYUNSET,@9) (#2,RANGEKEYUNSET,@5)}
 -
 PointKey: parsnip#3,1
@@ -154,7 +154,7 @@ Span: q-z:{(#14,RANGEKEYSET,@9,mangos)}
 PointKey: parsnip#3,1
 Span: <invalid>
 -
-PointKey: l#72057594037927935,21
+PointKey: l#72057594037927935,20
 Span: l-m:{(#2,RANGEKEYUNSET,@9) (#2,RANGEKEYUNSET,@5)}
 -
 PointKey: parsnip#3,1
@@ -281,7 +281,7 @@ Span: e-f:{(#20,RANGEKEYSET,@5,pineapple) (#20,RANGEKEYSET,@3,guava)}
 PointKey: e#2,1
 Span: e-f:{(#20,RANGEKEYSET,@5,pineapple) (#20,RANGEKEYSET,@3,guava)}
 -
-PointKey: h#72057594037927935,21
+PointKey: h#72057594037927935,19
 Span: h-j:{(#22,RANGEKEYDEL) (#21,RANGEKEYSET,@5,peaches) (#21,RANGEKEYSET,@3,starfruit)}
 -
 
@@ -510,13 +510,13 @@ last
 seek-ge a
 seek-lt d
 ----
-PointKey: b#72057594037927935,21
+PointKey: b#72057594037927935,19
 Span: b-d:{(#5,RANGEKEYDEL)}
 -
-PointKey: f#72057594037927935,21
+PointKey: f#72057594037927935,19
 Span: f-g:{(#6,RANGEKEYDEL)}
 -
-PointKey: b#72057594037927935,21
+PointKey: b#72057594037927935,19
 Span: b-d:{(#5,RANGEKEYDEL)}
 -
 PointKey: c#8,1
@@ -548,7 +548,7 @@ Span: w-y:{(#5,RANGEKEYSET,@1,v1)}
 PointKey: x#8,1
 Span: w-y:{(#5,RANGEKEYSET,@1,v1)}
 -
-PointKey: y#72057594037927935,21
+PointKey: y#72057594037927935,19
 Span: y-z:{(#5,RANGEKEYDEL)}
 -
 

internal/keyspan/testdata/interleaving_iter_masking

@@ -307,7 +307,7 @@ next
 next
 next
 ----
-PointKey: a#72057594037927935,21
+PointKey: a#72057594037927935,20
 Span: a-c:{(#1,RANGEKEYUNSET,@5) (#1,RANGEKEYUNSET,@2)}
 -
 PointKey: a#1,1
@@ -332,7 +332,7 @@ Span: a-c:{(#1,RANGEKEYUNSET,@5) (#1,RANGEKEYUNSET,@2)}
 PointKey: a#1,1
 Span: a-c:{(#1,RANGEKEYUNSET,@5) (#1,RANGEKEYUNSET,@2)}
 -
-PointKey: a#72057594037927935,21
+PointKey: a#72057594037927935,20
 Span: a-c:{(#1,RANGEKEYUNSET,@5) (#1,RANGEKEYUNSET,@2)}
 -
 .