sstable: use sync.Pool for interval block collectors

Author: RaduBerinde

Diff for: iterator_test.go

@@ -280,6 +280,9 @@ func (c *minSeqNumPropertyCollector) SupportsSuffixReplacement() bool {
 	return false
 }
 
+// Close is part of the BlockPropertyCollector interface.
+func (c *minSeqNumPropertyCollector) Close() {}
+
 // minSeqNumFilter is a BlockPropertyFilter that uses the
 // minSeqNumPropertyCollector data to filter out entire tables.
 type minSeqNumFilter struct {

Diff for: sstable/block_property.go

@@ -131,6 +131,10 @@ type BlockPropertyCollector interface {
 	// Finish appends the property value to buf and resets the collector to an
 	// empty state.
 	Finish(buf []byte) []byte
+
+	// Close can be used to allow the implementation to be reused in the future.
+	// Once Close is called, the object must no longer be used.
+	Close()
 }
 
 // BlockPropertyFilter is used in an Iterator to filter sstables and blocks
@@ -250,11 +254,19 @@ func NewBlockIntervalCollector(
 	if mapper == nil {
 		panic("mapper must be provided")
 	}
-	return &BlockIntervalCollector{
+	c := blockIntervalCollectorPool.Get().(*BlockIntervalCollector)
+	*c = BlockIntervalCollector{
 		name:           name,
 		mapper:         mapper,
 		suffixReplacer: suffixReplacer,
 	}
+	return c
+}
+
+var blockIntervalCollectorPool = sync.Pool{
+	New: func() interface{} {
+		return &BlockIntervalCollector{}
+	},
 }
 
 // Name is part of the BlockPropertyCollector interface.
@@ -328,6 +340,12 @@ func (b *BlockIntervalCollector) Finish(buf []byte) []byte {
 	return result
 }
 
+// Close is part of the BlockPropertyCollector interface.
+func (b *BlockIntervalCollector) Close() {
+	*b = BlockIntervalCollector{}
+	blockIntervalCollectorPool.Put(b)
+}
+
 // BlockInterval represents the [Lower, Upper) interval of 64-bit values
 // corresponding to a set of keys. The meaning of the values themselves is
 // opaque to the BlockIntervalCollector.

Diff for: sstable/block_property_obsolete.go

@@ -50,6 +50,9 @@ func (o *obsoleteKeyBlockPropertyCollector) Finish(buf []byte) []byte {
 	return res
 }
 
+// Close is part of the BlockPropertyCollector interface.
+func (o *obsoleteKeyBlockPropertyCollector) Close() {}
+
 // AddCollected is part of the BlockPropertyCollector interface.
 func (o *obsoleteKeyBlockPropertyCollector) AddCollected(oldProp []byte) error {
 	isObsolete, err := obsoleteKeyBlockPropertyDecode(oldProp)

Diff for: sstable/block_property_test.go

@@ -1369,6 +1369,9 @@ func (p *keyCountCollector) SupportsSuffixReplacement() bool {
 	return true
 }
 
+// Close is part of the BlockPropertyCollector interface.
+func (p *keyCountCollector) Close() {}
+
 type intSuffixIntervalMapper struct {
 	suffixLen int
 }

Diff for: sstable/writer.go

@@ -2091,6 +2091,16 @@ func (w *Writer) Close() (err error) {
 	indexBlockBufPool.Put(w.indexBlock)
 	w.indexBlock = nil
 
+	// Close property collectors. Closing is optional, we don't need to do it in
+	// error paths.
+	for _, p := range w.blockPropCollectors {
+		p.dataBlock.Close()
+		p.indexBlock.Close()
+		p.rangeKeyBlock.Close()
+		p.table.Close()
+	}
+	w.blockPropCollectors = nil
+
 	// Make any future calls to Set or Close return an error.
 	w.err = errWriterClosed
 	return nil