Summary: Similar to v2 (db and table code understands prefixes), but use ReadOptions as in v3. Also, make the CreateFilter code faster and cleaner. Test Plan: make db_test; export LEVELDB_TESTS=PrefixScan; ./db_test Reviewers: dhruba Reviewed By: dhruba CC: haobo, emayanke Differential Revision: https://reviews.facebook.net/D12027main
Tyler Harter
12 years ago
parent
3b81df34bd
commit
f5f1842282
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// Wrap an underlying iterator, but exclude any results not starting
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// with a given prefix. Seeking to keys not beginning with the prefix
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// is invalid, and SeekToLast is not implemented (that would be
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// non-trivial), but otherwise this iterator will behave just like the
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// underlying iterator would if there happened to be no non-matching
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// keys in the dataset.
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#ifndef STORAGE_LEVELDB_DB_PREFIX_FILTER_ITERATOR_H_ |
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#define STORAGE_LEVELDB_DB_PREFIX_FILTER_ITERATOR_H_ |
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#include "leveldb/iterator.h" |
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namespace leveldb { |
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class PrefixFilterIterator : public Iterator { |
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private: |
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Iterator* iter_; |
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const Slice &prefix_; |
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const SliceTransform *prefix_extractor_; |
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Status status_; |
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public: |
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PrefixFilterIterator(Iterator* iter, |
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const Slice &prefix, |
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const SliceTransform* prefix_extractor) |
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: iter_(iter), prefix_(prefix), |
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prefix_extractor_(prefix_extractor), |
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status_(Status::OK()) { |
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if (prefix_extractor == nullptr) { |
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status_ = Status::InvalidArgument("A prefix filter may not be used " |
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"unless a function is also defined " |
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"for extracting prefixes"); |
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} else if (!prefix_extractor_->InRange(prefix)) { |
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status_ = Status::InvalidArgument("Must provide a slice for prefix which" |
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"is a prefix for some key"); |
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} |
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} |
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~PrefixFilterIterator() { |
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delete iter_; |
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} |
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Slice key() const { return iter_->key(); } |
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Slice value() const { return iter_->value(); } |
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Status status() const { |
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if (!status_.ok()) { |
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return status_; |
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} |
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return iter_->status(); |
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} |
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void Next() { iter_->Next(); } |
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void Prev() { iter_->Prev(); } |
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void Seek(const Slice& k) { |
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if (prefix_extractor_->Transform(k) == prefix_) { |
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iter_->Seek(k); |
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} else { |
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status_ = Status::InvalidArgument("Seek must begin with target prefix"); |
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} |
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} |
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void SeekToFirst() { |
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Seek(prefix_); |
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} |
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void SeekToLast() { |
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status_ = Status::NotSupported("SeekToLast is incompatible with prefixes"); |
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} |
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bool Valid() const { |
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return (status_.ok() && iter_->Valid() && |
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prefix_extractor_->Transform(iter_->key()) == prefix_); |
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} |
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}; |
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} // namespace leveldb
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#endif |
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@ -0,0 +1,41 @@ |
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// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// Class for specifying user-defined functions which perform a
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// transformation on a slice. It is not required that every slice
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// belong to the domain and/or range of a function. Subclasses should
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// define InDomain and InRange to determine which slices are in either
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// of these sets respectively.
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#ifndef STORAGE_LEVELDB_INCLUDE_SLICE_TRANSFORM_H_ |
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#define STORAGE_LEVELDB_INCLUDE_SLICE_TRANSFORM_H_ |
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#include <string> |
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namespace leveldb { |
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class Slice; |
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class SliceTransform { |
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public: |
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virtual ~SliceTransform() {}; |
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// Return the name of this transformation.
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virtual const char* Name() const = 0; |
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// transform a src in domain to a dst in the range
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virtual Slice Transform(const Slice& src) const = 0; |
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// determine whether this is a valid src upon the function applies
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virtual bool InDomain(const Slice& src) const = 0; |
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// determine whether dst=Transform(src) for some src
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virtual bool InRange(const Slice& dst) const = 0; |
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}; |
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extern const SliceTransform* NewFixedPrefixTransform(size_t prefix_len); |
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} |
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#endif // STORAGE_LEVELDB_INCLUDE_SLICE_TRANSFORM_H_
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@ -0,0 +1,43 @@ |
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// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include "leveldb/slice_transform.h" |
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#include "leveldb/slice.h" |
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namespace leveldb { |
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namespace { |
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class FixedPrefixTransform : public SliceTransform { |
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private: |
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size_t prefix_len_; |
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public: |
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explicit FixedPrefixTransform(size_t prefix_len) : prefix_len_(prefix_len) { } |
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virtual const char* Name() const { |
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return "rocksdb.FixedPrefix"; |
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} |
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virtual Slice Transform(const Slice& src) const { |
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assert(InDomain(src)); |
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return Slice(src.data(), prefix_len_); |
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} |
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virtual bool InDomain(const Slice& src) const { |
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return (src.size() >= prefix_len_); |
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} |
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virtual bool InRange(const Slice& dst) const { |
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return (dst.size() == prefix_len_); |
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} |
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}; |
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} |
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const SliceTransform* NewFixedPrefixTransform(size_t prefix_len) { |
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return new FixedPrefixTransform(prefix_len); |
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} |
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} // namespace leveldb
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