sstable: capture elided prefix in a prop

sstable/properties.go

@@ -134,6 +134,9 @@ type Properties struct {
  CompressionOptions string `prop:"rocksdb.compression_options"`
  // The total size of all data blocks.
  DataSize uint64 `prop:"rocksdb.data.size"`
+ // ElidedPrefix is the byte prefix, if any, that was elided from every key and
+ // key span during the construction of the sstable.
+ ElidedPrefix string `prop:"pebble.elided_prefix"`
  // The external sstable version format. Version 2 is the one RocksDB has been
  // using since 5.13. RocksDB only uses the global sequence number for an
  // sstable if this property has been set.
@@ -428,7 +431,9 @@ func (p *Properties) save(tblFormat TableFormat, w *rawBlockWriter) {
  p.saveUvarint(m, unsafe.Offsetof(p.ValueBlocksSize), p.ValueBlocksSize)
  }
  p.saveBool(m, unsafe.Offsetof(p.WholeKeyFiltering), p.WholeKeyFiltering)
-
+ if p.ElidedPrefix != "" {
+ p.saveString(m, unsafe.Offsetof(p.ElidedPrefix), p.ElidedPrefix)
+ }
  if tblFormat < TableFormatPebblev1 {
  m["rocksdb.column.family.id"] = binary.AppendUvarint([]byte(nil), math.MaxInt32)
  m["rocksdb.fixed.key.length"] = []byte{0x00}

sstable/testdata/writer

@@ -369,7 +369,7 @@ layout
  821 footer (53)
  874 EOF
 
-build elide-prefix=foo_
+build elide-prefix=foo_ props=(elided)
 foo_a.SET.1:a
 foo_b.DEL.2:
 foo_c.MERGE.3:c
@@ -386,3 +386,5 @@ point: [a#1,1-h#7,2]
 rangedel: [d#4,15-j#72057594037927935,15]
 rangekey: [j#9,19-m#72057594037927935,21]
 seqnums: [1-11]
+props "elided":
+ pebble.elided_prefix: foo_

sstable/writer.go

@@ -2303,6 +2303,7 @@ func NewWriter(writable objstorage.Writable, o WriterOptions, extraOpts ...Write
  w.props.MergerName = o.MergerName
  w.props.PropertyCollectorNames = "[]"
  w.props.ExternalFormatVersion = rocksDBExternalFormatVersion
+ w.props.ElidedPrefix = string(o.ElidePrefix)
 
  if len(o.BlockPropertyCollectors) > 0 || w.tableFormat >= TableFormatPebblev4 {
  var buf bytes.Buffer