foedus::storage::hash::HashMetadata Struct Reference

Metadata of an hash storage. More...

Detailed Description

Metadata of an hash storage.

Definition at line 40 of file hash_metadata.hpp.

#include <hash_metadata.hpp>

Inheritance diagram for foedus::storage::hash::HashMetadata:

Collaboration diagram for foedus::storage::hash::HashMetadata:

Public Member Functions
	HashMetadata ()
	HashMetadata (StorageId id, const StorageName &name, uint8_t bin_bits)
	HashMetadata (const StorageName &name, uint8_t bin_bits=kHashMinBinBits)
	This one is for newly creating a storage. More...
void	set_capacity (uint64_t expected_records, double preferred_records_per_bin=5.0)
	Use this method to set an appropriate value for bin_bits_. More...
uint64_t	get_bin_count () const
	Number of bins in this hash storage. More...
uint8_t	get_bin_shifts () const
HashBin	extract_bin (HashValue hash) const
std::string	describe () const
Public Member Functions inherited from foedus::storage::Metadata
	Metadata ()
	Metadata (StorageId id, StorageType type, const StorageName &name)
	Metadata (StorageId id, StorageType type, const StorageName &name, SnapshotPagePointer root_snapshot_page_id)
bool	keeps_all_volatile_pages () const

Public Attributes
uint8_t	bin_bits_
	Number of bins in exponent of two. More...
uint8_t	pad1_
uint16_t	pad2_
uint32_t	pad3_
Public Attributes inherited from foedus::storage::Metadata
StorageId	id_
	the unique ID of this storage. More...
StorageType	type_
	type of the storage. More...
StorageName	name_
	the unique name of this storage. More...
SnapshotPagePointer	root_snapshot_page_id_
	Pointer to a snapshotted page this storage is rooted at. More...
SnapshotThresholds	snapshot_thresholds_

Friends
std::ostream &	operator<< (std::ostream &o, const HashMetadata &v)

Additional Inherited Members
Static Public Member Functions inherited from foedus::storage::Metadata
static std::string	describe (const Metadata &metadata)
	to_string operator of all Metadata objects. More...

Constructor & Destructor Documentation

foedus::storage::hash::HashMetadata::HashMetadata ( )

inline

Definition at line 41 of file hash_metadata.hpp.

    : Metadata(0, kHashStorage, ""), bin_bits_(kHashMinBinBits), pad1_(0), pad2_(0), pad3_(0) {}

foedus::storage::hash::HashMetadata::HashMetadata ( StorageId  id, const StorageName &  name, uint8_t  bin_bits  )

inline

Definition at line 43 of file hash_metadata.hpp.

    : Metadata(id, kHashStorage, name), bin_bits_(bin_bits), pad1_(0), pad2_(0), pad3_(0) {
  }

foedus::storage::hash::HashMetadata::HashMetadata ( const StorageName &  name, uint8_t  bin_bits = kHashMinBinBits  )

inline

This one is for newly creating a storage.

Definition at line 47 of file hash_metadata.hpp.

    : Metadata(0, kHashStorage, name), bin_bits_(bin_bits), pad1_(0), pad2_(0), pad3_(0) {
  }

Member Function Documentation

std::string foedus::storage::hash::HashMetadata::describe

(

)

const

Definition at line 29 of file hash_metadata.cpp.

                                       {
  std::stringstream o;
  o << HashMetadataSerializer(const_cast<HashMetadata*>(this));
  return o.str();
}

HashBin foedus::storage::hash::HashMetadata::extract_bin ( HashValue  hash ) const

inline

Definition at line 65 of file hash_metadata.hpp.

References get_bin_shifts().

{ return hash >> get_bin_shifts(); }

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uint64_t foedus::storage::hash::HashMetadata::get_bin_count ( ) const

inline

Number of bins in this hash storage.

Always power of two.

Definition at line 62 of file hash_metadata.hpp.

References bin_bits_.

Referenced by foedus::storage::hash::HashStoragePimpl::create(), and foedus::storage::hash::HashStoragePimpl::get_bin_count().

{ return 1ULL << bin_bits_; }

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uint8_t foedus::storage::hash::HashMetadata::get_bin_shifts ( ) const

inline

Returns

how many bits we should shift down to extract bins from hashes

Definition at line 64 of file hash_metadata.hpp.

References bin_bits_.

Referenced by extract_bin(), foedus::storage::hash::HashStoragePimpl::get_bin_shifts(), and foedus::storage::hash::HashCombo::HashCombo().

{ return 64U - bin_bits_; }

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void foedus::storage::hash::HashMetadata::set_capacity	(	uint64_t	expected_records,
		double	preferred_records_per_bin = 5.0
	)

Use this method to set an appropriate value for bin_bits_.

Parameters

[in]	expected_records	how many records do you expect to store in this storage
[in]	preferred_records_per_bin	average records per a hash bin. 5-30 are recommended. If this number is too large, many bins have a linked-list rather than just one page.

Definition at line 51 of file hash_metadata.cpp.

References ASSERT_ND, bin_bits_, foedus::storage::hash::kHashMaxBinBits, and foedus::storage::hash::kHashMinBinBits.

                                                                                           {
  if (expected_records == 0) {
    expected_records = 1;
  }
  if (preferred_records_per_bin < 1) {
    preferred_records_per_bin = 1;
  }
  uint64_t bin_count = expected_records / preferred_records_per_bin;
  uint8_t bits;
  for (bits = 0; bits < kHashMaxBinBits && ((1ULL << bits) < bin_count); ++bits) {
    continue;
  }
  if (bits < kHashMinBinBits) {
    bits = kHashMinBinBits;
  }
  bin_bits_ = bits;
  ASSERT_ND(bin_bits_ >= kHashMinBinBits);
  ASSERT_ND(bin_bits_ <= kHashMaxBinBits);
}

Friends And Related Function Documentation

std::ostream& operator<< ( std::ostream &  o, const HashMetadata &  v  )

friend

Definition at line 34 of file hash_metadata.cpp.

                                                             {
  o << HashMetadataSerializer(const_cast<HashMetadata*>(&v));
  return o;
}

Member Data Documentation

uint8_t foedus::storage::hash::HashMetadata::bin_bits_

Number of bins in exponent of two.

Recommended to use set_capacity() to set this value.

Invariant

kHashMinBinBits <= bin_bits_ <= kHashMaxBinBits

Definition at line 75 of file hash_metadata.hpp.

Referenced by foedus::storage::hash::HashStoragePimpl::get_bin_bits(), get_bin_count(), get_bin_shifts(), foedus::storage::hash::HashMetadataSerializer::load(), foedus::storage::hash::operator<<(), foedus::storage::hash::HashMetadataSerializer::save(), and set_capacity().

uint8_t foedus::storage::hash::HashMetadata::pad1_

Definition at line 78 of file hash_metadata.hpp.

uint16_t foedus::storage::hash::HashMetadata::pad2_

Definition at line 79 of file hash_metadata.hpp.

uint32_t foedus::storage::hash::HashMetadata::pad3_

Definition at line 80 of file hash_metadata.hpp.

---

The documentation for this struct was generated from the following files:

• /home/shino/foedus_code/foedus-core/include/foedus/storage/hash/hash_metadata.hpp
• /home/shino/foedus_code/foedus-core/src/foedus/storage/hash/hash_metadata.cpp