iterator: Start on correct value when reverse=true

Closes facebook#27
Nazgolze · Mar 30, 2013 · 701b3c0 · 701b3c0
1 parent 1a566fe
commit 701b3c0
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Showing 2 changed files with 28 additions and 3 deletions.
diff --git a/src/iterator.cc b/src/iterator.cc
@@ -59,8 +59,15 @@ Iterator::~Iterator () {
 bool Iterator::GetIterator () {
  if (dbIterator == NULL) {
  dbIterator = database->NewIterator(options);
- if (start != NULL)
+ if (start != NULL) {
  dbIterator->Seek(*start);
+ if (reverse) {
+ if (!dbIterator->Valid())
+ dbIterator->SeekToLast();
+ else if (start->compare(dbIterator->key()))
+ dbIterator->Prev();
+ }
+ }
  else if (reverse)
  dbIterator->SeekToLast();
  else

diff --git a/test/iterator-test.js b/test/iterator-test.js
@@ -230,8 +230,8 @@ module.exports.iterator = function (leveldown) {
  test('test iterator with start being a midway key and reverse=true', function (t) {
  collectEntries(db.iterator({ keyAsBuffer: false, valueAsBuffer: false, start: '49.5', reverse: true }), function (err, data) {
  t.notOk(err, 'no error')
- t.equal(data.length, 51, 'correct number of entries')
- var expected = sourceData.slice().reverse().slice(49).map(transformSource)
+ t.equal(data.length, 50, 'correct number of entries')
+ var expected = sourceData.slice().reverse().slice(50).map(transformSource)
  t.deepEqual(data, expected)
  t.end()
  })
@@ -365,6 +365,24 @@ module.exports.iterator = function (leveldown) {
  t.end()
  })
  })
+
+ test('test iterator with start after database end and reverse=true', function (t) {
+ collectEntries(db.iterator({ keyAsBuffer: false, valueAsBuffer: false, start: '9a', reverse: true }), function (err, data) {
+ t.notOk(err, 'no error')
+ t.equal(data.length, sourceData.length, 'correct number of entries')
+ var expected = sourceData.slice().reverse().map(transformSource)
+ t.deepEqual(data, expected)
+ t.end()
+ })
+ })
+
+ test('test iterator with start and end after database and and reverse=true', function (t) {
+ collectEntries(db.iterator({ start: '9b', end: '9a', reverse: true }), function (err, data) {
+ t.notOk(err, 'no error')
+ t.equal(data.length, 0, 'correct number of entries')
+ t.end()
+ })
+ })
 }
 
 module.exports.tearDown = function () {