src/kudu/common/scan_spec.h

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.
#pragma once

#include <cstdint>
#include <string>
#include <unordered_map>
#include <vector>

#include <boost/optional/optional.hpp>
#include <glog/logging.h>

#include "kudu/common/column_predicate.h" // IWYU pragma: keep
#include "kudu/util/slice.h"

namespace kudu {

class Arena;
class ColumnSchema;
class EncodedKey;
class Partition;
class PartitionSchema;
class Schema;

class ScanSpec {
 public:
  ScanSpec()
    : lower_bound_key_(nullptr),
      exclusive_upper_bound_key_(nullptr),
      cache_blocks_(true),
      limit_(boost::none) {
  }

  // Add a predicate on the column.
  //
  // The new predicate is merged into the existing predicate for the column.
  void AddPredicate(ColumnPredicate pred);

  // Remove the predicate for the column.
  void RemovePredicate(const std::string& column_name);

  // Removes all column predicates.
  void RemovePredicates();

  // Returns true if the result set is known to be empty.
  bool CanShortCircuit() const;

  // Returns true if a Bloom filter predicate is present.
  bool ContainsBloomFilterPredicate() const;

  // Optimizes the scan by unifying the lower and upper bound constraints and
  // the column predicates.
  //
  // If remove_pushed_predicates is true, then column predicates that are pushed
  // into the upper or lower primary key bounds are removed.
  //
  // Idempotent.
  void OptimizeScan(const Schema& schema,
                    Arena* arena,
                    bool remove_pushed_predicates);

  // Filter in-list predicate values with given hash partition schema.
  // If range partition is introduced when creating table, in-list predicate
  // can also benefit from this pruning.
  //
  // Only supports pruning for single-column hash schemas or single-column range schema.
  // Now support hash prune on:
  //     hash(onekey), # support.
  //     range(onekey), # support.
  //     hash(onekey), hash(anotherkey) # support either.
  //     hash(onekey), range(anotherkey) # support either.
  //     hash(key_one, key_two), hash(anotherkey) # only support prune on anotherkey.
  //     range(key_one, key_two) # not support.
  //
  // TODO(ningw) For IN list predicate on hash/range(key_one, key_two) or more columns,
  // if one predicate is IN list, and the rest predicate(s) are EQUAL, could
  // have IN list predicate values prune as well.
  void PruneInlistValuesIfPossible(const Schema& schema,
                                   const Partition& partition,
                                   const PartitionSchema& partition_schema);

  // Get columns that are present in the predicates but not in the projection
  std::vector<ColumnSchema> GetMissingColumns(const Schema& projection);

  // Set the lower bound (inclusive) primary key for the scan.
  // Does not take ownership of 'key', which must remain valid.
  // If called multiple times, the most restrictive key will be used.
  void SetLowerBoundKey(const EncodedKey* key);

  // Set the upper bound (exclusive) primary key for the scan.
  // Does not take ownership of 'key', which must remain valid.
  // If called multiple times, the most restrictive key will be used.
  void SetExclusiveUpperBoundKey(const EncodedKey* key);

  // Sets the lower bound (inclusive) partition key for the scan.
  //
  // The scan spec makes a copy of 'slice'; the caller may free it afterward.
  //
  // Only used in the client.
  void SetLowerBoundPartitionKey(const Slice& slice);

  // Sets the upper bound (exclusive) partition key for the scan.
  //
  // The scan spec makes a copy of 'slice'; the caller may free it afterward.
  //
  // Only used in the client.
  void SetExclusiveUpperBoundPartitionKey(const Slice& slice);

  // Returns the scan predicates.
  const std::unordered_map<std::string, ColumnPredicate>& predicates() const {
    return predicates_;
  }

  const EncodedKey* lower_bound_key() const {
    return lower_bound_key_;
  }

  const EncodedKey* exclusive_upper_bound_key() const {
    return exclusive_upper_bound_key_;
  }

  const std::string& lower_bound_partition_key() const {
    return lower_bound_partition_key_;
  }
  const std::string& exclusive_upper_bound_partition_key() const {
    return exclusive_upper_bound_partition_key_;
  }

  bool cache_blocks() const {
    return cache_blocks_;
  }

  void set_cache_blocks(bool cache_blocks) {
    cache_blocks_ = cache_blocks;
  }

  bool has_limit() const {
    return limit_ != boost::none;
  }

  void set_limit(int64_t limit) {
    limit_ = limit;
  }

  int64_t limit() const {
    CHECK(has_limit());
    return *limit_;
  }

  std::string ToString(const Schema& schema) const;

 private:

  // Lift implicit predicates specified as part of the lower and upper bound
  // primary key constraints into the simplified predicate bounds.
  //
  // When the lower and exclusive upper bound primary keys have a prefix of
  // equal components, the components can be lifted into an equality predicate
  // over their associated column. Optionally, a single (pair) of range
  // predicates can be lifted from the key component following the prefix of
  // equal components.
  void LiftPrimaryKeyBounds(const Schema& schema, Arena* arena);

  // Encode the column predicates into lower and upper primary key bounds, and
  // replace the existing bounds if the new bounds are more constrained.
  //
  // If remove_pushed_predicates is true, then the predicates in the primary key
  // bound will be removed if the bound is replaced.
  void PushPredicatesIntoPrimaryKeyBounds(const Schema& schema,
                                          Arena* arena,
                                          bool remove_pushed_predicates);

  std::unordered_map<std::string, ColumnPredicate> predicates_;
  const EncodedKey* lower_bound_key_;
  const EncodedKey* exclusive_upper_bound_key_;
  std::string lower_bound_partition_key_;
  std::string exclusive_upper_bound_partition_key_;
  bool cache_blocks_;
  boost::optional<int64_t> limit_;
};

} // namespace kudu