[CF] NewIterators

Summary: Adding the last missing function -- NewIterators(). Pretty simple implementation

Test Plan: added a unit test

Reviewers: dhruba, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16689

db/column_family_test.cc

@@ -788,6 +788,63 @@ TEST(ColumnFamilyTest, DifferentCompactionStyles) {
   Close();
 }
 
+namespace {
+std::string IterStatus(Iterator* iter) {
+  std::string result;
+  if (iter->Valid()) {
+    result = iter->key().ToString() + "->" + iter->value().ToString();
+  } else {
+    result = "(invalid)";
+  }
+  return result;
+}
+}  // namespace anonymous
+
+TEST(ColumnFamilyTest, NewIteratorsTest) {
+  // iter == 0 -- no tailing
+  // iter == 2 -- tailing
+  for (int iter = 0; iter < 2; ++iter) {
+    Open();
+    CreateColumnFamiliesAndReopen({"one", "two"});
+    ASSERT_OK(Put(0, "a", "b"));
+    ASSERT_OK(Put(1, "b", "a"));
+    ASSERT_OK(Put(2, "c", "m"));
+    ASSERT_OK(Put(2, "v", "t"));
+    std::vector<Iterator*> iterators;
+    ReadOptions options;
+    options.tailing = (iter == 1);
+    ASSERT_OK(db_->NewIterators(options, handles_, &iterators));
+
+    for (auto it : iterators) {
+      it->SeekToFirst();
+    }
+    ASSERT_EQ(IterStatus(iterators[0]), "a->b");
+    ASSERT_EQ(IterStatus(iterators[1]), "b->a");
+    ASSERT_EQ(IterStatus(iterators[2]), "c->m");
+
+    ASSERT_OK(Put(1, "x", "x"));
+
+    for (auto it : iterators) {
+      it->Next();
+    }
+
+    ASSERT_EQ(IterStatus(iterators[0]), "(invalid)");
+    if (iter == 0) {
+      // no tailing
+      ASSERT_EQ(IterStatus(iterators[1]), "(invalid)");
+    } else {
+      // tailing
+      ASSERT_EQ(IterStatus(iterators[1]), "x->x");
+    }
+    ASSERT_EQ(IterStatus(iterators[2]), "v->t");
+
+    for (auto it : iterators) {
+      delete it;
+    }
+    Destroy();
+  }
+}
+
 }  // namespace rocksdb
 
 int main(int argc, char** argv) {

db/db_impl.cc

@@ -3214,12 +3214,12 @@ Iterator* DBImpl::NewIterator(const ReadOptions& options,
   SuperVersion* super_version = nullptr;
   auto cfh = reinterpret_cast<ColumnFamilyHandleImpl*>(column_family);
   auto cfd = cfh->cfd();
-  mutex_.Lock();
   if (!options.tailing) {
+    mutex_.Lock();
     super_version = cfd->GetSuperVersion()->Ref();
     latest_snapshot = versions_->LastSequence();
+    mutex_.Unlock();
   }
-  mutex_.Unlock();
 
   Iterator* iter;
   if (options.tailing) {
@@ -3227,11 +3227,12 @@ Iterator* DBImpl::NewIterator(const ReadOptions& options,
   } else {
     iter = NewInternalIterator(options, cfd, super_version);
 
-    iter = NewDBIterator(
-        &dbname_, env_, *cfd->full_options(), cfd->user_comparator(), iter,
-        (options.snapshot != nullptr
-             ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
-             : latest_snapshot));
+    auto snapshot =
+        options.snapshot != nullptr
+            ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
+            : latest_snapshot;
+    iter = NewDBIterator(&dbname_, env_, *cfd->full_options(),
+                         cfd->user_comparator(), iter, snapshot);
   }
 
   if (options.prefix) {
@@ -3245,10 +3246,53 @@ Iterator* DBImpl::NewIterator(const ReadOptions& options,
 
 Status DBImpl::NewIterators(
     const ReadOptions& options,
-    const std::vector<ColumnFamilyHandle*>& column_family,
+    const std::vector<ColumnFamilyHandle*>& column_families,
     std::vector<Iterator*>* iterators) {
-  // TODO(icanadi)
-  return Status::NotSupported("Not yet!");
+
+  if (options.prefix) {
+    return Status::NotSupported(
+        "NewIterators doesn't support ReadOptions::prefix");
+  }
+
+  iterators->clear();
+  iterators->reserve(column_families.size());
+  SequenceNumber latest_snapshot = 0;
+  std::vector<SuperVersion*> super_versions;
+  super_versions.reserve(column_families.size());
+
+  if (!options.tailing) {
+    mutex_.Lock();
+    latest_snapshot = versions_->LastSequence();
+    for (auto cfh : column_families) {
+      auto cfd = reinterpret_cast<ColumnFamilyHandleImpl*>(cfh)->cfd();
+      super_versions.push_back(cfd->GetSuperVersion()->Ref());
+    }
+    mutex_.Unlock();
+  }
+
+  if (options.tailing) {
+    for (auto cfh : column_families) {
+      auto cfd = reinterpret_cast<ColumnFamilyHandleImpl*>(cfh)->cfd();
+      iterators->push_back(new TailingIterator(this, options, cfd));
+    }
+  } else {
+    for (size_t i = 0; i < column_families.size(); ++i) {
+      auto cfh = reinterpret_cast<ColumnFamilyHandleImpl*>(column_families[i]);
+      auto cfd = cfh->cfd();
+
+      auto snapshot =
+          options.snapshot != nullptr
+              ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
+              : latest_snapshot;
+
+      auto iter = NewInternalIterator(options, cfd, super_versions[i]);
+      iter = NewDBIterator(&dbname_, env_, *cfd->full_options(),
+                           cfd->user_comparator(), iter, snapshot);
+      iterators->push_back(iter);
+    }
+  }
+
+  return Status::OK();
 }
 
 const Snapshot* DBImpl::GetSnapshot() {

db/db_impl.h

@@ -86,7 +86,7 @@ class DBImpl : public DB {
                                 ColumnFamilyHandle* column_family);
   virtual Status NewIterators(
       const ReadOptions& options,
-      const std::vector<ColumnFamilyHandle*>& column_family,
+      const std::vector<ColumnFamilyHandle*>& column_families,
       std::vector<Iterator*>* iterators);
   virtual const Snapshot* GetSnapshot();
   virtual void ReleaseSnapshot(const Snapshot* snapshot);

include/rocksdb/db.h

@@ -255,7 +255,7 @@ class DB {
   // before the db is deleted
   virtual Status NewIterators(
       const ReadOptions& options,
-      const std::vector<ColumnFamilyHandle*>& column_family,
+      const std::vector<ColumnFamilyHandle*>& column_families,
       std::vector<Iterator*>* iterators) = 0;
 
   // Return a handle to the current DB state.  Iterators created with

include/utilities/stackable_db.h

@@ -80,9 +80,9 @@ class StackableDB : public DB {
 
   virtual Status NewIterators(
       const ReadOptions& options,
-      const std::vector<ColumnFamilyHandle*>& column_family,
+      const std::vector<ColumnFamilyHandle*>& column_families,
       std::vector<Iterator*>* iterators) {
-    return db_->NewIterators(options, column_family, iterators);
+    return db_->NewIterators(options, column_families, iterators);
   }