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Eliminate some redundant block reads.

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Summary:
Re-use metadata for reading Compression Dictionary on BlockBased
  table open, this saves two reads from disk.
  This helps to our 999 percentile in 5.6.1 where prefetch buffer is  not present.
Closes https://github.com/facebook/rocksdb/pull/3354

Differential Revision: D6695753

Pulled By: ajkr

fbshipit-source-id: bb8acd9e9e66e65b89c548ab8940570ae360333c
This commit is contained in:
Dmitri Smirnov 2018-01-10 17:03:12 -08:00 committed by Facebook Github Bot
parent 0c6e8be9e2
commit b010116d82
3 changed files with 20 additions and 14 deletions
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26
table/block_based_table_reader.cc
View File

@ -759,23 +759,27 @@ Status BlockBasedTable::Open(const ImmutableCFOptions& ioptions,
// Read the compression dictionary meta block
bool found_compression_dict;
s = SeekToCompressionDictBlock(meta_iter.get(), &found_compression_dict);
BlockHandle compression_dict_handle;
s = SeekToCompressionDictBlock(meta_iter.get(), &found_compression_dict,
&compression_dict_handle);
if (!s.ok()) {
ROCKS_LOG_WARN(
rep->ioptions.info_log,
"Error when seeking to compression dictionary block from file: %s",
s.ToString().c_str());
} else if (found_compression_dict) {
} else if (found_compression_dict && !compression_dict_handle.IsNull()) {
// TODO(andrewkr): Add to block cache if cache_index_and_filter_blocks is
// true.
unique_ptr<BlockContents> compression_dict_block{new BlockContents()};
// TODO(andrewkr): ReadMetaBlock repeats SeekToCompressionDictBlock().
// maybe decode a handle from meta_iter
// and do ReadBlockContents(handle) instead
s = rocksdb::ReadMetaBlock(rep->file.get(), prefetch_buffer.get(),
file_size, kBlockBasedTableMagicNumber,
rep->ioptions, rocksdb::kCompressionDictBlock,
compression_dict_block.get());
std::unique_ptr<BlockContents> compression_dict_cont{new BlockContents()};
PersistentCacheOptions cache_options;
ReadOptions read_options;
read_options.verify_checksums = false;
BlockFetcher compression_block_fetcher(
rep->file.get(), prefetch_buffer.get(), rep->footer, read_options,
compression_dict_handle, compression_dict_cont.get(), rep->ioptions, false /* decompress */,
Slice() /*compression dict*/, cache_options);
s = compression_block_fetcher.ReadBlockContents();
if (!s.ok()) {
ROCKS_LOG_WARN(
rep->ioptions.info_log,
@ -783,7 +787,7 @@ Status BlockBasedTable::Open(const ImmutableCFOptions& ioptions,
"block %s",
s.ToString().c_str());
} else {
rep->compression_dict_block = std::move(compression_dict_block);
rep->compression_dict_block = std::move(compression_dict_cont);
}
}

5
table/table_properties.cc
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@ -215,8 +215,9 @@ Status SeekToPropertiesBlock(InternalIterator* meta_iter, bool* is_found) {
// Seek to the compression dictionary block.
// Return true if it successfully seeks to that block.
Status SeekToCompressionDictBlock(InternalIterator* meta_iter, bool* is_found) {
return SeekToMetaBlock(meta_iter, kCompressionDictBlock, is_found);
Status SeekToCompressionDictBlock(InternalIterator* meta_iter, bool* is_found,
BlockHandle* block_handle) {
return SeekToMetaBlock(meta_iter, kCompressionDictBlock, is_found, block_handle);
}
Status SeekToRangeDelBlock(InternalIterator* meta_iter, bool* is_found,

3
table/table_properties_internal.h
View File

@ -21,7 +21,8 @@ Status SeekToPropertiesBlock(InternalIterator* meta_iter, bool* is_found);
// Seek to the compression dictionary block.
// If it successfully seeks to the properties block, "is_found" will be
// set to true.
Status SeekToCompressionDictBlock(InternalIterator* meta_iter, bool* is_found);
Status SeekToCompressionDictBlock(InternalIterator* meta_iter, bool* is_found,
BlockHandle* block_handle);
// TODO(andrewkr) should not put all meta block in table_properties.h/cc
Status SeekToRangeDelBlock(InternalIterator* meta_iter, bool* is_found,