tsdb: shrink txRing with smaller integers

4 billion active transactions ought to be enough for anyone.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

tsdb/head_read.go

@@ -724,7 +724,7 @@ func (s *memSeries) iterator(id chunks.HeadChunkID, c chunkenc.Chunk, isoState *
 
 		// Removing the extra transactionIDs that are relevant for samples that
 		// come after this chunk, from the total transactionIDs.
-		appendIDsToConsider := s.txs.txIDCount - (totalSamples - (previousSamples + numSamples))
+		appendIDsToConsider := int(s.txs.txIDCount) - (totalSamples - (previousSamples + numSamples))
 
 		// Iterate over the appendIDs, find the first one that the isolation state says not
 		// to return.

tsdb/head_test.go

@@ -2550,7 +2550,7 @@ func TestIsolationAppendIDZeroIsNoop(t *testing.T) {
 
 	ok, _ := s.append(0, 0, 0, cOpts)
 	require.True(t, ok, "Series append failed.")
-	require.Equal(t, 0, s.txs.txIDCount, "Series should not have an appendID after append with appendID=0.")
+	require.Equal(t, 0, int(s.txs.txIDCount), "Series should not have an appendID after append with appendID=0.")
 }
 
 func TestHeadSeriesChunkRace(t *testing.T) {

tsdb/isolation.go

@@ -240,8 +240,8 @@ func (i *isolation) closeAppend(appendID uint64) {
 // The transactionID ring buffer.
 type txRing struct {
 	txIDs     []uint64
-	txIDFirst int // Position of the first id in the ring.
+	txIDFirst uint32 // Position of the first id in the ring.
-	txIDCount int // How many ids in the ring.
+	txIDCount uint32 // How many ids in the ring.
 }
 
 func newTxRing(capacity int) *txRing {
@@ -251,7 +251,7 @@ func newTxRing(capacity int) *txRing {
 }
 
 func (txr *txRing) add(appendID uint64) {
-	if txr.txIDCount == len(txr.txIDs) {
+	if int(txr.txIDCount) == len(txr.txIDs) {
 		// Ring buffer is full, expand by doubling.
 		newRing := make([]uint64, txr.txIDCount*2)
 		idx := copy(newRing, txr.txIDs[txr.txIDFirst:])
@@ -260,12 +260,12 @@ func (txr *txRing) add(appendID uint64) {
 		txr.txIDFirst = 0
 	}
 
-	txr.txIDs[(txr.txIDFirst+txr.txIDCount)%len(txr.txIDs)] = appendID
+	txr.txIDs[int(txr.txIDFirst+txr.txIDCount)%len(txr.txIDs)] = appendID
 	txr.txIDCount++
 }
 
 func (txr *txRing) cleanupAppendIDsBelow(bound uint64) {
-	pos := txr.txIDFirst
+	pos := int(txr.txIDFirst)
 
 	for txr.txIDCount > 0 {
 		if txr.txIDs[pos] < bound {
@@ -281,7 +281,7 @@ func (txr *txRing) cleanupAppendIDsBelow(bound uint64) {
 		}
 	}
 
-	txr.txIDFirst %= len(txr.txIDs)
+	txr.txIDFirst %= uint32(len(txr.txIDs))
 }
 
 func (txr *txRing) iterator() *txRingIterator {
@@ -296,7 +296,7 @@ func (txr *txRing) iterator() *txRingIterator {
 type txRingIterator struct {
 	ids []uint64
 
-	pos int
+	pos uint32
 }
 
 func (it *txRingIterator) At() uint64 {
@@ -305,7 +305,7 @@ func (it *txRingIterator) At() uint64 {
 
 func (it *txRingIterator) Next() {
 	it.pos++
-	if it.pos == len(it.ids) {
+	if int(it.pos) == len(it.ids) {
 		it.pos = 0
 	}
 }