8b84390517
Summary: Respect the scan upper bound/limit, if specified, in `MultiScan`. This applies to block based table and other native RocksDB SSTs. In order to properly support it, the `MultiScan` object caches the `ReadOptions` passed by the user and sets the `iterate_upper_bound` as appropriate. We optimize for the case of either all scans specifying the upper bound, or none of them. In case of mixed scans, we reallocate the DB iterator anytime `ReadOptions` has to be updated. Tests: New unit tests in `db_iterator_test` Pull Request resolved: https://github.com/facebook/rocksdb/pull/13723 Reviewed By: cbi42 Differential Revision: D77385049 Pulled By: anand1976 fbshipit-source-id: 9c02d125770cbedbe6e8c10767ba537e7f7540e1
70 lines
2.5 KiB
C++
70 lines
2.5 KiB
C++
// Copyright (c) Meta Platforms, Inc. and affiliates.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#include "rocksdb/db.h"
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namespace ROCKSDB_NAMESPACE {
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using MultiScanIterator = MultiScan::MultiScanIterator;
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MultiScan::MultiScan(const ReadOptions& read_options,
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const std::vector<ScanOptions>& scan_opts, DB* db,
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ColumnFamilyHandle* cfh)
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: read_options_(read_options), scan_opts_(scan_opts), db_(db), cfh_(cfh) {
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bool slow_path = false;
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// Setup read_options with iterate_uuper_bound based on the first scan.
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// Subsequent scans will update and allocate a new DB iterator as necessary
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if (scan_opts[0].range.limit) {
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upper_bound_ = *scan_opts[0].range.limit;
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read_options_.iterate_upper_bound = &upper_bound_;
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} else {
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read_options_.iterate_upper_bound = nullptr;
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}
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for (auto opts : scan_opts) {
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// Check that all the ScanOptions either specify an upper bound or not. If
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// its mixed we take the slow path which avoids calling Prepare: we have to
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// reallocate the Iterator with updated read_options everytime we switch
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// between upper bound or no upper bound, which complicates Prepare.
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if (opts.range.limit.has_value() != scan_opts[0].range.limit.has_value()) {
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slow_path = true;
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break;
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}
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}
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db_iter_.reset(db->NewIterator(read_options_, cfh));
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if (!slow_path) {
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db_iter_->Prepare(scan_opts);
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}
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}
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MultiScanIterator& MultiScanIterator::operator++() {
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if (idx_ >= scan_opts_.size()) {
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throw std::logic_error("Index out of range");
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}
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idx_++;
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if (idx_ < scan_opts_.size()) {
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// Check if we need to update read_options_
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if (scan_opts_[idx_].range.limit.has_value() !=
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(read_options_.iterate_upper_bound != nullptr)) {
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if (scan_opts_[idx_].range.limit) {
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*upper_bound_ = *scan_opts_[idx_].range.limit;
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read_options_.iterate_upper_bound = upper_bound_;
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} else {
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read_options_.iterate_upper_bound = nullptr;
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}
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db_iter_.reset(db_->NewIterator(read_options_, cfh_));
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scan_.Reset(db_iter_.get());
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} else if (scan_opts_[idx_].range.limit) {
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*upper_bound_ = *scan_opts_[idx_].range.limit;
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}
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db_iter_->Seek(*scan_opts_[idx_].range.start);
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status_ = db_iter_->status();
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if (!status_.ok()) {
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throw MultiScanException(status_);
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}
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}
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return *this;
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}
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} // namespace ROCKSDB_NAMESPACE
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