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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "table/block_based/partitioned_index_iterator.h"
namespace ROCKSDB_NAMESPACE {
void PartitionedIndexIterator::Seek(const Slice& target) { SeekImpl(&target); }
void PartitionedIndexIterator::SeekToFirst() { SeekImpl(nullptr); }
void PartitionedIndexIterator::SeekImpl(const Slice* target) {
SavePrevIndexValue();
if (target) {
index_iter_->Seek(*target);
} else {
index_iter_->SeekToFirst();
}
if (!index_iter_->Valid()) {
ResetPartitionedIndexIter();
return;
}
InitPartitionedIndexBlock();
if (target) {
block_iter_.Seek(*target);
} else {
block_iter_.SeekToFirst();
}
FindKeyForward();
// We could check upper bound here, but that would be too complicated
// and checking index upper bound is less useful than for data blocks.
if (target) {
assert(!Valid() || (table_->get_rep()->index_key_includes_seq
? (icomp_.Compare(*target, key()) <= 0)
: (user_comparator_.Compare(ExtractUserKey(*target),
key()) <= 0)));
}
}
void PartitionedIndexIterator::SeekToLast() {
SavePrevIndexValue();
index_iter_->SeekToLast();
if (!index_iter_->Valid()) {
ResetPartitionedIndexIter();
return;
}
InitPartitionedIndexBlock();
block_iter_.SeekToLast();
FindKeyBackward();
}
void PartitionedIndexIterator::Next() {
assert(block_iter_points_to_real_block_);
block_iter_.Next();
FindKeyForward();
}
void PartitionedIndexIterator::Prev() {
assert(block_iter_points_to_real_block_);
block_iter_.Prev();
FindKeyBackward();
}
void PartitionedIndexIterator::InitPartitionedIndexBlock() {
BlockHandle partitioned_index_handle = index_iter_->value().handle;
if (!block_iter_points_to_real_block_ ||
partitioned_index_handle.offset() != prev_block_offset_ ||
// if previous attempt of reading the block missed cache, try again
block_iter_.status().IsIncomplete()) {
if (block_iter_points_to_real_block_) {
ResetPartitionedIndexIter();
}
auto* rep = table_->get_rep();
bool is_for_compaction =
lookup_context_.caller == TableReaderCaller::kCompaction;
// Prefetch additional data for range scans (iterators).
// Implicit auto readahead:
// Enabled after 2 sequential IOs when ReadOptions.readahead_size == 0.
// Explicit user requested readahead:
// Enabled from the very first IO when ReadOptions.readahead_size is set.
block_prefetcher_.PrefetchIfNeeded(
rep, partitioned_index_handle, read_options_.readahead_size,
is_for_compaction, /*no_sequential_checking=*/false, read_options_,
/*readaheadsize_cb=*/nullptr, /*is_async_io_prefetch=*/false);
Status s;
table_->NewDataBlockIterator<IndexBlockIter>(
read_options_, partitioned_index_handle, &block_iter_,
BlockType::kIndex,
/*get_context=*/nullptr, &lookup_context_,
block_prefetcher_.prefetch_buffer(),
/*for_compaction=*/is_for_compaction, /*async_read=*/false, s,
/*use_block_cache_for_lookup=*/true);
block_iter_points_to_real_block_ = true;
// We could check upper bound here but it is complicated to reason about
// upper bound in index iterator. On the other than, in large scans, index
// iterators are moved much less frequently compared to data blocks. So
// the upper bound check is skipped for simplicity.
}
}
void PartitionedIndexIterator::FindKeyForward() {
// This method's code is kept short to make it likely to be inlined.
assert(block_iter_points_to_real_block_);
if (!block_iter_.Valid()) {
// This is the only call site of FindBlockForward(), but it's extracted into
// a separate method to keep FindKeyForward() short and likely to be
// inlined. When transitioning to a different block, we call
// FindBlockForward(), which is much longer and is probably not inlined.
FindBlockForward();
} else {
// This is the fast path that avoids a function call.
}
}
void PartitionedIndexIterator::FindBlockForward() {
// TODO the while loop inherits from two-level-iterator. We don't know
// whether a block can be empty so it can be replaced by an "if".
do {
if (!block_iter_.status().ok()) {
return;
}
ResetPartitionedIndexIter();
index_iter_->Next();
if (!index_iter_->Valid()) {
return;
}
InitPartitionedIndexBlock();
block_iter_.SeekToFirst();
} while (!block_iter_.Valid());
}
void PartitionedIndexIterator::FindKeyBackward() {
while (!block_iter_.Valid()) {
if (!block_iter_.status().ok()) {
return;
}
ResetPartitionedIndexIter();
index_iter_->Prev();
if (index_iter_->Valid()) {
InitPartitionedIndexBlock();
block_iter_.SeekToLast();
} else {
return;
}
}
}
} // namespace ROCKSDB_NAMESPACE
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