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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
commit | e6918187568dbd01842d8d1d2c808ce16a894239 (patch) | |
tree | 64f88b554b444a49f656b6c656111a145cbbaa28 /src/rocksdb/table/block_based/block_based_table_iterator.cc | |
parent | Initial commit. (diff) | |
download | ceph-e6918187568dbd01842d8d1d2c808ce16a894239.tar.xz ceph-e6918187568dbd01842d8d1d2c808ce16a894239.zip |
Adding upstream version 18.2.2.upstream/18.2.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | src/rocksdb/table/block_based/block_based_table_iterator.cc | 459 |
1 files changed, 459 insertions, 0 deletions
diff --git a/src/rocksdb/table/block_based/block_based_table_iterator.cc b/src/rocksdb/table/block_based/block_based_table_iterator.cc new file mode 100644 index 000000000..d2605670f --- /dev/null +++ b/src/rocksdb/table/block_based/block_based_table_iterator.cc @@ -0,0 +1,459 @@ +// 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/block_based_table_iterator.h" + +namespace ROCKSDB_NAMESPACE { + +void BlockBasedTableIterator::SeekToFirst() { SeekImpl(nullptr, false); } + +void BlockBasedTableIterator::Seek(const Slice& target) { + SeekImpl(&target, true); +} + +void BlockBasedTableIterator::SeekImpl(const Slice* target, + bool async_prefetch) { + bool is_first_pass = true; + if (async_read_in_progress_) { + AsyncInitDataBlock(false); + is_first_pass = false; + } + + is_out_of_bound_ = false; + is_at_first_key_from_index_ = false; + if (target && !CheckPrefixMayMatch(*target, IterDirection::kForward)) { + ResetDataIter(); + return; + } + + bool need_seek_index = true; + if (block_iter_points_to_real_block_ && block_iter_.Valid()) { + // Reseek. + prev_block_offset_ = index_iter_->value().handle.offset(); + + if (target) { + // We can avoid an index seek if: + // 1. The new seek key is larger than the current key + // 2. The new seek key is within the upper bound of the block + // Since we don't necessarily know the internal key for either + // the current key or the upper bound, we check user keys and + // exclude the equality case. Considering internal keys can + // improve for the boundary cases, but it would complicate the + // code. + if (user_comparator_.Compare(ExtractUserKey(*target), + block_iter_.user_key()) > 0 && + user_comparator_.Compare(ExtractUserKey(*target), + index_iter_->user_key()) < 0) { + need_seek_index = false; + } + } + } + + if (need_seek_index) { + if (target) { + index_iter_->Seek(*target); + } else { + index_iter_->SeekToFirst(); + } + + if (!index_iter_->Valid()) { + ResetDataIter(); + return; + } + } + + IndexValue v = index_iter_->value(); + const bool same_block = block_iter_points_to_real_block_ && + v.handle.offset() == prev_block_offset_; + + if (!v.first_internal_key.empty() && !same_block && + (!target || icomp_.Compare(*target, v.first_internal_key) <= 0) && + allow_unprepared_value_) { + // Index contains the first key of the block, and it's >= target. + // We can defer reading the block. + is_at_first_key_from_index_ = true; + // ResetDataIter() will invalidate block_iter_. Thus, there is no need to + // call CheckDataBlockWithinUpperBound() to check for iterate_upper_bound + // as that will be done later when the data block is actually read. + ResetDataIter(); + } else { + // Need to use the data block. + if (!same_block) { + if (read_options_.async_io && async_prefetch) { + if (is_first_pass) { + AsyncInitDataBlock(is_first_pass); + } + if (async_read_in_progress_) { + // Status::TryAgain indicates asynchronous request for retrieval of + // data blocks has been submitted. So it should return at this point + // and Seek should be called again to retrieve the requested block and + // execute the remaining code. + return; + } + } else { + InitDataBlock(); + } + } else { + // When the user does a reseek, the iterate_upper_bound might have + // changed. CheckDataBlockWithinUpperBound() needs to be called + // explicitly if the reseek ends up in the same data block. + // If the reseek ends up in a different block, InitDataBlock() will do + // the iterator upper bound check. + CheckDataBlockWithinUpperBound(); + } + + if (target) { + block_iter_.Seek(*target); + } else { + block_iter_.SeekToFirst(); + } + FindKeyForward(); + } + + CheckOutOfBound(); + + if (target) { + assert(!Valid() || icomp_.Compare(*target, key()) <= 0); + } +} + +void BlockBasedTableIterator::SeekForPrev(const Slice& target) { + is_out_of_bound_ = false; + is_at_first_key_from_index_ = false; + // For now totally disable prefix seek in auto prefix mode because we don't + // have logic + if (!CheckPrefixMayMatch(target, IterDirection::kBackward)) { + ResetDataIter(); + return; + } + + SavePrevIndexValue(); + + // Call Seek() rather than SeekForPrev() in the index block, because the + // target data block will likely to contain the position for `target`, the + // same as Seek(), rather than than before. + // For example, if we have three data blocks, each containing two keys: + // [2, 4] [6, 8] [10, 12] + // (the keys in the index block would be [4, 8, 12]) + // and the user calls SeekForPrev(7), we need to go to the second block, + // just like if they call Seek(7). + // The only case where the block is difference is when they seek to a position + // in the boundary. For example, if they SeekForPrev(5), we should go to the + // first block, rather than the second. However, we don't have the information + // to distinguish the two unless we read the second block. In this case, we'll + // end up with reading two blocks. + index_iter_->Seek(target); + + if (!index_iter_->Valid()) { + auto seek_status = index_iter_->status(); + // Check for IO error + if (!seek_status.IsNotFound() && !seek_status.ok()) { + ResetDataIter(); + return; + } + + // With prefix index, Seek() returns NotFound if the prefix doesn't exist + if (seek_status.IsNotFound()) { + // Any key less than the target is fine for prefix seek + ResetDataIter(); + return; + } else { + index_iter_->SeekToLast(); + } + // Check for IO error + if (!index_iter_->Valid()) { + ResetDataIter(); + return; + } + } + + InitDataBlock(); + + block_iter_.SeekForPrev(target); + + FindKeyBackward(); + CheckDataBlockWithinUpperBound(); + assert(!block_iter_.Valid() || + icomp_.Compare(target, block_iter_.key()) >= 0); +} + +void BlockBasedTableIterator::SeekToLast() { + is_out_of_bound_ = false; + is_at_first_key_from_index_ = false; + SavePrevIndexValue(); + index_iter_->SeekToLast(); + if (!index_iter_->Valid()) { + ResetDataIter(); + return; + } + InitDataBlock(); + block_iter_.SeekToLast(); + FindKeyBackward(); + CheckDataBlockWithinUpperBound(); +} + +void BlockBasedTableIterator::Next() { + if (is_at_first_key_from_index_ && !MaterializeCurrentBlock()) { + return; + } + assert(block_iter_points_to_real_block_); + block_iter_.Next(); + FindKeyForward(); + CheckOutOfBound(); +} + +bool BlockBasedTableIterator::NextAndGetResult(IterateResult* result) { + Next(); + bool is_valid = Valid(); + if (is_valid) { + result->key = key(); + result->bound_check_result = UpperBoundCheckResult(); + result->value_prepared = !is_at_first_key_from_index_; + } + return is_valid; +} + +void BlockBasedTableIterator::Prev() { + if (is_at_first_key_from_index_) { + is_at_first_key_from_index_ = false; + + index_iter_->Prev(); + if (!index_iter_->Valid()) { + return; + } + + InitDataBlock(); + block_iter_.SeekToLast(); + } else { + assert(block_iter_points_to_real_block_); + block_iter_.Prev(); + } + + FindKeyBackward(); +} + +void BlockBasedTableIterator::InitDataBlock() { + BlockHandle data_block_handle = index_iter_->value().handle; + if (!block_iter_points_to_real_block_ || + data_block_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_) { + ResetDataIter(); + } + 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, data_block_handle, read_options_.readahead_size, is_for_compaction, + /*no_sequential_checking=*/false, read_options_.rate_limiter_priority); + Status s; + table_->NewDataBlockIterator<DataBlockIter>( + read_options_, data_block_handle, &block_iter_, BlockType::kData, + /*get_context=*/nullptr, &lookup_context_, + block_prefetcher_.prefetch_buffer(), + /*for_compaction=*/is_for_compaction, /*async_read=*/false, s); + block_iter_points_to_real_block_ = true; + CheckDataBlockWithinUpperBound(); + } +} + +void BlockBasedTableIterator::AsyncInitDataBlock(bool is_first_pass) { + BlockHandle data_block_handle = index_iter_->value().handle; + bool is_for_compaction = + lookup_context_.caller == TableReaderCaller::kCompaction; + if (is_first_pass) { + if (!block_iter_points_to_real_block_ || + data_block_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_) { + ResetDataIter(); + } + auto* rep = table_->get_rep(); + // 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. + // In case of async_io with Implicit readahead, block_prefetcher_ will + // always the create the prefetch buffer by setting no_sequential_checking + // = true. + block_prefetcher_.PrefetchIfNeeded( + rep, data_block_handle, read_options_.readahead_size, + is_for_compaction, /*no_sequential_checking=*/read_options_.async_io, + read_options_.rate_limiter_priority); + + Status s; + table_->NewDataBlockIterator<DataBlockIter>( + read_options_, data_block_handle, &block_iter_, BlockType::kData, + /*get_context=*/nullptr, &lookup_context_, + block_prefetcher_.prefetch_buffer(), + /*for_compaction=*/is_for_compaction, /*async_read=*/true, s); + + if (s.IsTryAgain()) { + async_read_in_progress_ = true; + return; + } + } + } else { + // Second pass will call the Poll to get the data block which has been + // requested asynchronously. + Status s; + table_->NewDataBlockIterator<DataBlockIter>( + read_options_, data_block_handle, &block_iter_, BlockType::kData, + /*get_context=*/nullptr, &lookup_context_, + block_prefetcher_.prefetch_buffer(), + /*for_compaction=*/is_for_compaction, /*async_read=*/false, s); + } + block_iter_points_to_real_block_ = true; + CheckDataBlockWithinUpperBound(); + async_read_in_progress_ = false; +} + +bool BlockBasedTableIterator::MaterializeCurrentBlock() { + assert(is_at_first_key_from_index_); + assert(!block_iter_points_to_real_block_); + assert(index_iter_->Valid()); + + is_at_first_key_from_index_ = false; + InitDataBlock(); + assert(block_iter_points_to_real_block_); + + if (!block_iter_.status().ok()) { + return false; + } + + block_iter_.SeekToFirst(); + + if (!block_iter_.Valid() || + icomp_.Compare(block_iter_.key(), + index_iter_->value().first_internal_key) != 0) { + block_iter_.Invalidate(Status::Corruption( + "first key in index doesn't match first key in block")); + return false; + } + + return true; +} + +void BlockBasedTableIterator::FindKeyForward() { + // This method's code is kept short to make it likely to be inlined. + + assert(!is_out_of_bound_); + 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 BlockBasedTableIterator::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; + } + // Whether next data block is out of upper bound, if there is one. + const bool next_block_is_out_of_bound = + read_options_.iterate_upper_bound != nullptr && + block_iter_points_to_real_block_ && + block_upper_bound_check_ == BlockUpperBound::kUpperBoundInCurBlock; + assert(!next_block_is_out_of_bound || + user_comparator_.CompareWithoutTimestamp( + *read_options_.iterate_upper_bound, /*a_has_ts=*/false, + index_iter_->user_key(), /*b_has_ts=*/true) <= 0); + ResetDataIter(); + index_iter_->Next(); + if (next_block_is_out_of_bound) { + // The next block is out of bound. No need to read it. + TEST_SYNC_POINT_CALLBACK("BlockBasedTableIterator:out_of_bound", nullptr); + // We need to make sure this is not the last data block before setting + // is_out_of_bound_, since the index key for the last data block can be + // larger than smallest key of the next file on the same level. + if (index_iter_->Valid()) { + is_out_of_bound_ = true; + } + return; + } + + if (!index_iter_->Valid()) { + return; + } + + IndexValue v = index_iter_->value(); + + if (!v.first_internal_key.empty() && allow_unprepared_value_) { + // Index contains the first key of the block. Defer reading the block. + is_at_first_key_from_index_ = true; + return; + } + + InitDataBlock(); + block_iter_.SeekToFirst(); + } while (!block_iter_.Valid()); +} + +void BlockBasedTableIterator::FindKeyBackward() { + while (!block_iter_.Valid()) { + if (!block_iter_.status().ok()) { + return; + } + + ResetDataIter(); + index_iter_->Prev(); + + if (index_iter_->Valid()) { + InitDataBlock(); + block_iter_.SeekToLast(); + } else { + return; + } + } + + // We could have check lower bound here too, but we opt not to do it for + // code simplicity. +} + +void BlockBasedTableIterator::CheckOutOfBound() { + if (read_options_.iterate_upper_bound != nullptr && + block_upper_bound_check_ != BlockUpperBound::kUpperBoundBeyondCurBlock && + Valid()) { + is_out_of_bound_ = + user_comparator_.CompareWithoutTimestamp( + *read_options_.iterate_upper_bound, /*a_has_ts=*/false, user_key(), + /*b_has_ts=*/true) <= 0; + } +} + +void BlockBasedTableIterator::CheckDataBlockWithinUpperBound() { + if (read_options_.iterate_upper_bound != nullptr && + block_iter_points_to_real_block_) { + block_upper_bound_check_ = (user_comparator_.CompareWithoutTimestamp( + *read_options_.iterate_upper_bound, + /*a_has_ts=*/false, index_iter_->user_key(), + /*b_has_ts=*/true) > 0) + ? BlockUpperBound::kUpperBoundBeyondCurBlock + : BlockUpperBound::kUpperBoundInCurBlock; + } +} +} // namespace ROCKSDB_NAMESPACE |