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 () {