func (db *DB) newIterator(seq uint64, slice *util.Range, ro *opt.ReadOptions) *dbIter {
var islice *util.Range
if slice != nil {
islice = &util.Range{}
if slice.Start != nil {
islice.Start = newIkey(slice.Start, kMaxSeq, ktSeek)
}
if slice.Limit != nil {
islice.Limit = newIkey(slice.Limit, kMaxSeq, ktSeek)
}
}
rawIter := db.newRawIterator(islice, ro)
iter := &dbIter{
db: db,
icmp: db.s.icmp,
iter: rawIter,
seq: seq,
strict: opt.GetStrict(db.s.o.Options, ro, opt.StrictReader),
key: make([]byte, 0),
value: make([]byte, 0),
}
atomic.AddInt32(&db.aliveIters, 1)
runtime.SetFinalizer(iter, (*dbIter).Release)
return iter
}
func (v *version) getIterators(slice *util.Range, ro *opt.ReadOptions) (its []iterator.Iterator) {
// Merge all level zero files together since they may overlap
for _, t := range v.tables[0] {
it := v.s.tops.newIterator(t, slice, ro)
its = append(its, it)
}
strict := opt.GetStrict(v.s.o.Options, ro, opt.StrictReader)
for _, tables := range v.tables[1:] {
if len(tables) == 0 {
continue
}
it := iterator.NewIndexedIterator(tables.newIndexIterator(v.s.tops, v.s.icmp, slice, ro), strict)
its = append(its, it)
}
return
}
func (db *DB) newRawIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
em, fm := db.getMems()
v := db.s.version()
ti := v.getIterators(slice, ro)
n := len(ti) + 2
i := make([]iterator.Iterator, 0, n)
emi := em.mdb.NewIterator(slice)
emi.SetReleaser(&memdbReleaser{m: em})
i = append(i, emi)
if fm != nil {
fmi := fm.mdb.NewIterator(slice)
fmi.SetReleaser(&memdbReleaser{m: fm})
i = append(i, fmi)
}
i = append(i, ti...)
strict := opt.GetStrict(db.s.o.Options, ro, opt.StrictReader)
mi := iterator.NewMergedIterator(i, db.s.icmp, strict)
mi.SetReleaser(&versionReleaser{v: v})
return mi
}
// NewIterator creates an iterator from the table.
//
// Slice allows slicing the iterator to only contains keys in the given
// range. A nil Range.Start is treated as a key before all keys in the
// table. And a nil Range.Limit is treated as a key after all keys in
// the table.
//
// The returned iterator is not goroutine-safe and should be released
// when not used.
//
// Also read Iterator documentation of the leveldb/iterator package.
func (r *Reader) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
r.mu.RLock()
defer r.mu.RUnlock()
if r.err != nil {
return iterator.NewEmptyIterator(r.err)
}
fillCache := !ro.GetDontFillCache()
indexBlock, rel, err := r.getIndexBlock(fillCache)
if err != nil {
return iterator.NewEmptyIterator(err)
}
index := &indexIter{
blockIter: r.newBlockIter(indexBlock, rel, slice, true),
tr: r,
slice: slice,
fillCache: !ro.GetDontFillCache(),
}
return iterator.NewIndexedIterator(index, opt.GetStrict(r.o, ro, opt.StrictReader))
}