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FOEDUS Core Library
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foedus::storage::hash::RecordLocation Struct Reference

return value of locate_record(). More...

Detailed Description

return value of locate_record().

Notes on XID, MOCC Locking, read-set, and "physical_only"
This object also contains observed_, which is guaranteed to be the XID at or before the return from locate_record(). There is a notable contract here. When locking in MOCC kicks in, we want to make sure we return the value of XID after the lock to eliminate a chance of false verification failure. However, this means we need to take lock and register read-set within locate_record(). This caused us headaches for the following reason.
Logical vs Physical search in hash pages
Physically finding a record for given key in our hash page has the following guarantees.
  • When it finds a record, the record was at least at some point a valid (non-moved/non-being-written) record of the given key.
  • When it doesn't find any record, the page(s) at least at some point didn't contain any valid record of the given key.
On the other hand, it still allows the following behaviors:
  • The found record is now being moved or modified.
  • The page or its next page(s) is now newly inserting a physical record of the given key.
Logically finding a record provides additional guarantee to protect against the above at pre-commit time. It additionally takes read-set, page-version set, or even MOCC locks.
locate_record(): Logical or Physical
We initially designed locate_record() as a physical-only search operation separated from logical operations (e.g., get_record/overwrite_record, or the caller). Separation makes each of them simpler and more flexible. The logical side can separately decide, using an operation-specific logic, whether/when it will add the XID observed in locate_record() to read-set or not. The physical side (locate_record()) can be dumb simple, too.

But, seems like this is now unavoidable. Hence now locate_record() is a logical operation. To allow the caller to choose what to do logically, we receive a paramter physical_only. When false, locate_record might take logical lock and add the XID to readset, hence what locate_record() observed is protected. When true, locate_record never takes lock or adds it to readset. It just physically locates a record that was at least at some point a valid record. In this case, the caller is responsible to do appropriate thing to protect from concurrent modifications.

Definition at line 76 of file hash_record_location.hpp.

#include <hash_record_location.hpp>

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Public Member Functions

bool is_found () const
 
uint16_t get_aligned_key_length () const
 
uint16_t get_max_payload () const
 
void clear ()
 
ErrorCode populate_logical (xct::Xct *cur_xct, HashDataPage *page, DataPageSlotIndex index, bool intended_for_write)
 Populates the result with XID and possibly readset. More...
 
void populate_physical (HashDataPage *page, DataPageSlotIndex index)
 Populates fields other than readset_. More...
 

Public Attributes

HashDataPage * page_
 The data page (might not be bin-head) containing the record. More...
 
DataPageSlotIndex index_
 Index of the record in the page. More...
 
uint16_t cur_payload_length_
 Logical payload length as-of the observed XID. More...
 
uint16_t key_length_
 Key length of the slot, which is immutable. More...
 
uint16_t physical_record_length_
 Byte count the record of the slot occupies, which is immutable. More...
 
char * record_
 Address of the record. More...
 
xct::XctId observed_
 TID as of locate_record() identifying the record. More...
 
xct::ReadXctAccess * readset_
 If this method took a read-set on the returned record, points to the corresponding read-set. More...
 

Member Function Documentation

void foedus::storage::hash::RecordLocation::clear ( )
inline

Definition at line 114 of file hash_record_location.hpp.

References CXX11_NULLPTR, foedus::xct::XctId::data_, and foedus::storage::hash::kSlotNotFound.

Referenced by foedus::storage::hash::HashStoragePimpl::locate_record(), and foedus::storage::hash::HashStoragePimpl::locate_record_in_snapshot().

114  {
115  page_ = CXX11_NULLPTR;
116  index_ = kSlotNotFound;
117  cur_payload_length_ = 0;
118  key_length_ = 0;
119  physical_record_length_ = 0;
120  record_ = CXX11_NULLPTR;
121  observed_.data_ = 0;
122  readset_ = CXX11_NULLPTR;
123  }
foedus::storage::hash::RecordLocation::physical_record_length_
uint16_t physical_record_length_
Byte count the record of the slot occupies, which is immutable.
Definition: hash_record_location.hpp:90
CXX11_NULLPTR
#define CXX11_NULLPTR
Used in public headers in place of "nullptr" of C++11.
Definition: cxx11.hpp:132
foedus::storage::hash::kSlotNotFound
const DataPageSlotIndex kSlotNotFound
Definition: hash_id.hpp:197
foedus::storage::hash::RecordLocation::page_
HashDataPage * page_
The data page (might not be bin-head) containing the record.
Definition: hash_record_location.hpp:78
foedus::storage::hash::RecordLocation::record_
char * record_
Address of the record.
Definition: hash_record_location.hpp:93
foedus::storage::hash::RecordLocation::key_length_
uint16_t key_length_
Key length of the slot, which is immutable.
Definition: hash_record_location.hpp:88
foedus::storage::hash::RecordLocation::cur_payload_length_
uint16_t cur_payload_length_
Logical payload length as-of the observed XID.
Definition: hash_record_location.hpp:86
foedus::storage::hash::RecordLocation::observed_
xct::XctId observed_
TID as of locate_record() identifying the record.
Definition: hash_record_location.hpp:100
foedus::storage::hash::RecordLocation::readset_
xct::ReadXctAccess * readset_
If this method took a read-set on the returned record, points to the corresponding read-set...
Definition: hash_record_location.hpp:106
foedus::storage::hash::RecordLocation::index_
DataPageSlotIndex index_
Index of the record in the page.
Definition: hash_record_location.hpp:80

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uint16_t foedus::storage::hash::RecordLocation::get_aligned_key_length ( ) const
inline

Definition at line 109 of file hash_record_location.hpp.

References foedus::assorted::align8().

Referenced by get_max_payload(), foedus::storage::hash::HashStoragePimpl::get_record(), foedus::storage::hash::HashStoragePimpl::get_record_part(), and foedus::storage::hash::HashStoragePimpl::increment_record().

109 { return assorted::align8(key_length_); }
foedus::assorted::align8
T align8(T value)
8-alignment.
Definition: assorted_func.hpp:58
foedus::storage::hash::RecordLocation::key_length_
uint16_t key_length_
Key length of the slot, which is immutable.
Definition: hash_record_location.hpp:88

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uint16_t foedus::storage::hash::RecordLocation::get_max_payload ( ) const
inline

Definition at line 110 of file hash_record_location.hpp.

References get_aligned_key_length().

Referenced by foedus::storage::hash::HashStoragePimpl::insert_record(), and foedus::storage::hash::HashStoragePimpl::upsert_record().

110  {
111  return physical_record_length_ - get_aligned_key_length();
112  }
foedus::storage::hash::RecordLocation::physical_record_length_
uint16_t physical_record_length_
Byte count the record of the slot occupies, which is immutable.
Definition: hash_record_location.hpp:90

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bool foedus::storage::hash::RecordLocation::is_found ( ) const
inline

Definition at line 108 of file hash_record_location.hpp.

References foedus::storage::hash::kSlotNotFound.

Referenced by foedus::storage::hash::HashStoragePimpl::delete_record(), foedus::storage::hash::HashStoragePimpl::get_record(), foedus::storage::hash::HashStoragePimpl::get_record_part(), foedus::storage::hash::HashStoragePimpl::increment_record(), foedus::storage::hash::HashStoragePimpl::insert_record(), foedus::storage::hash::HashStoragePimpl::overwrite_record(), foedus::storage::hash::HashStoragePimpl::register_record_write_log(), and foedus::storage::hash::HashStoragePimpl::upsert_record().

108 { return index_ != kSlotNotFound; }
foedus::storage::hash::kSlotNotFound
const DataPageSlotIndex kSlotNotFound
Definition: hash_id.hpp:197
foedus::storage::hash::RecordLocation::index_
DataPageSlotIndex index_
Index of the record in the page.
Definition: hash_record_location.hpp:80

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ErrorCode foedus::storage::hash::RecordLocation::populate_logical ( xct::Xct *  cur_xct,
HashDataPage *  page,
DataPageSlotIndex  index,
bool  intended_for_write 
)

Populates the result with XID and possibly readset.

This is a logical operation that might take a readset.

Definition at line 27 of file hash_record_location.cpp.

References ASSERT_ND, CHECK_ERROR_CODE, cur_payload_length_, foedus::storage::hash::HashDataPage::get_slot_address(), index_, foedus::xct::XctId::is_being_written(), foedus::xct::XctId::is_moved(), foedus::xct::XctId::is_next_layer(), foedus::xct::XctId::is_valid(), foedus::kErrorCodeOk, key_length_, foedus::storage::hash::HashDataPage::Slot::key_length_, foedus::assorted::memory_fence_consume(), observed_, foedus::storage::hash::HashDataPage::Slot::offset_, foedus::xct::Xct::on_record_read(), page_, foedus::storage::hash::HashDataPage::Slot::payload_length_, physical_record_length_, foedus::storage::hash::HashDataPage::Slot::physical_record_length_, readset_, record_, foedus::storage::hash::HashDataPage::record_from_offset(), foedus::storage::hash::HashDataPage::Slot::tid_, and foedus::xct::RwLockableXctId::xct_id_.

Referenced by foedus::storage::hash::HashStoragePimpl::locate_record().

31  {
32  page_ = page;
33  index_ = index;
34  readset_ = nullptr;
35 
36  HashDataPage::Slot* slot = page->get_slot_address(index);
37  record_ = page->record_from_offset(slot->offset_);
38  key_length_ = slot->key_length_; // key_length is immutable, so just read it.
39  physical_record_length_ = slot->physical_record_length_; // immutable, too.
40 
41  // cur_payload_length_ is mutable, so must be retrieved _as of_ the XID.
42  // we thus need a retry loop.
43  while (true) {
44  xct::XctId before = slot->tid_.xct_id_;
45  assorted::memory_fence_consume();
46  cur_payload_length_ = slot->payload_length_;
47  assorted::memory_fence_consume();
48 
49  // [Logical check]: Read XID in a finalized fashion. If we found it "moved",
50  // then we don't need to remember it as read-set.
51  CHECK_ERROR_CODE(cur_xct->on_record_read(
52  intended_for_write,
53  &slot->tid_,
54  &observed_,
55  &readset_,
56  true, // no_readset_if_moved. see below
57  true)); // no_readset_if_next_layer. see below
58 
59  ASSERT_ND(!observed_.is_being_written());
60  ASSERT_ND(!observed_.is_next_layer()); // we don't use this flag in hash. never occurs
61  ASSERT_ND(observed_.is_valid());
62 
63  if (observed_ == before) {
64  // The consume fences make sure we are seeing in this order.
65  // 1. read "before"
66  // 2. read payload_length_
67  // 3. read observed_
68  // thus, observed==before guarantees that payload_length_ is *as of* observed_.
69  break;
70  }
71  }
72 
73  if (observed_.is_moved()) {
74  ASSERT_ND(readset_ == nullptr);
75  }
76  return kErrorCodeOk;
77 }
foedus::storage::hash::RecordLocation::physical_record_length_
uint16_t physical_record_length_
Byte count the record of the slot occupies, which is immutable.
Definition: hash_record_location.hpp:90
foedus::xct::XctId::is_valid
bool is_valid() const __attribute__((always_inline))
Definition: xct_id.hpp:973
foedus::storage::hash::RecordLocation::page_
HashDataPage * page_
The data page (might not be bin-head) containing the record.
Definition: hash_record_location.hpp:78
foedus::storage::hash::RecordLocation::record_
char * record_
Address of the record.
Definition: hash_record_location.hpp:93
foedus::kErrorCodeOk
0 means no-error.
Definition: error_code.hpp:87
foedus::storage::hash::RecordLocation::key_length_
uint16_t key_length_
Key length of the slot, which is immutable.
Definition: hash_record_location.hpp:88
foedus::storage::hash::RecordLocation::cur_payload_length_
uint16_t cur_payload_length_
Logical payload length as-of the observed XID.
Definition: hash_record_location.hpp:86
foedus::xct::XctId::is_next_layer
bool is_next_layer() const __attribute__((always_inline))
Definition: xct_id.hpp:1042
CHECK_ERROR_CODE
#define CHECK_ERROR_CODE(x)
This macro calls x and checks its returned error code.
Definition: error_code.hpp:155
foedus::storage::hash::RecordLocation::observed_
xct::XctId observed_
TID as of locate_record() identifying the record.
Definition: hash_record_location.hpp:100
foedus::xct::XctId::is_being_written
bool is_being_written() const __attribute__((always_inline))
Definition: xct_id.hpp:1038
foedus::assorted::memory_fence_consume
void memory_fence_consume()
Equivalent to std::atomic_thread_fence(std::memory_order_consume).
Definition: atomic_fences.hpp:81
foedus::storage::hash::RecordLocation::readset_
xct::ReadXctAccess * readset_
If this method took a read-set on the returned record, points to the corresponding read-set...
Definition: hash_record_location.hpp:106
foedus::xct::XctId::is_moved
bool is_moved() const __attribute__((always_inline))
Definition: xct_id.hpp:1041
ASSERT_ND
#define ASSERT_ND(x)
A warning-free wrapper macro of assert() that has no performance effect in release mode even when 'x'...
Definition: assert_nd.hpp:72
foedus::storage::hash::RecordLocation::index_
DataPageSlotIndex index_
Index of the record in the page.
Definition: hash_record_location.hpp:80

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void foedus::storage::hash::RecordLocation::populate_physical ( HashDataPage *  page,
DataPageSlotIndex  index 
)

Populates fields other than readset_.

This is a physical-only operation that never takes readset/locks.

Definition at line 79 of file hash_record_location.cpp.

References ASSERT_ND, cur_payload_length_, foedus::storage::hash::HashDataPage::get_slot_address(), index_, foedus::xct::XctId::is_being_written(), foedus::xct::XctId::is_next_layer(), foedus::xct::XctId::is_valid(), key_length_, foedus::storage::hash::HashDataPage::Slot::key_length_, observed_, foedus::storage::hash::HashDataPage::Slot::offset_, page_, foedus::storage::hash::HashDataPage::Slot::payload_length_, physical_record_length_, foedus::storage::hash::HashDataPage::Slot::physical_record_length_, readset_, record_, foedus::storage::hash::HashDataPage::record_from_offset(), foedus::xct::XctId::spin_while_being_written(), foedus::storage::hash::HashDataPage::Slot::tid_, and foedus::xct::RwLockableXctId::xct_id_.

Referenced by foedus::storage::hash::HashStoragePimpl::locate_record(), and foedus::storage::hash::HashStoragePimpl::locate_record_in_snapshot().

79  {
80  page_ = page;
81  index_ = index;
82  readset_ = nullptr;
83 
84  HashDataPage::Slot* slot = page->get_slot_address(index);
85  cur_payload_length_ = slot->payload_length_; // no worry on physical-only read.
86  key_length_ = slot->key_length_;
87  physical_record_length_ = slot->physical_record_length_;
88  record_ = page->record_from_offset(slot->offset_);
89  observed_ = slot->tid_.xct_id_.spin_while_being_written();
90  ASSERT_ND(!observed_.is_being_written());
91  ASSERT_ND(!observed_.is_next_layer()); // we don't use this flag in hash. never occurs
92  ASSERT_ND(observed_.is_valid());
93 }
foedus::storage::hash::RecordLocation::physical_record_length_
uint16_t physical_record_length_
Byte count the record of the slot occupies, which is immutable.
Definition: hash_record_location.hpp:90
foedus::xct::XctId::is_valid
bool is_valid() const __attribute__((always_inline))
Definition: xct_id.hpp:973
foedus::storage::hash::RecordLocation::page_
HashDataPage * page_
The data page (might not be bin-head) containing the record.
Definition: hash_record_location.hpp:78
foedus::storage::hash::RecordLocation::record_
char * record_
Address of the record.
Definition: hash_record_location.hpp:93
foedus::storage::hash::RecordLocation::key_length_
uint16_t key_length_
Key length of the slot, which is immutable.
Definition: hash_record_location.hpp:88
foedus::storage::hash::RecordLocation::cur_payload_length_
uint16_t cur_payload_length_
Logical payload length as-of the observed XID.
Definition: hash_record_location.hpp:86
foedus::xct::XctId::is_next_layer
bool is_next_layer() const __attribute__((always_inline))
Definition: xct_id.hpp:1042
foedus::storage::hash::RecordLocation::observed_
xct::XctId observed_
TID as of locate_record() identifying the record.
Definition: hash_record_location.hpp:100
foedus::xct::XctId::is_being_written
bool is_being_written() const __attribute__((always_inline))
Definition: xct_id.hpp:1038
foedus::xct::XctId::spin_while_being_written
XctId spin_while_being_written() const __attribute__((always_inline))
Returns a version of this Xid whose being_written flag is off.
Definition: xct_id.hpp:1190
foedus::storage::hash::RecordLocation::readset_
xct::ReadXctAccess * readset_
If this method took a read-set on the returned record, points to the corresponding read-set...
Definition: hash_record_location.hpp:106
ASSERT_ND
#define ASSERT_ND(x)
A warning-free wrapper macro of assert() that has no performance effect in release mode even when 'x'...
Definition: assert_nd.hpp:72
foedus::storage::hash::RecordLocation::index_
DataPageSlotIndex index_
Index of the record in the page.
Definition: hash_record_location.hpp:80

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Member Data Documentation

uint16_t foedus::storage::hash::RecordLocation::cur_payload_length_

Logical payload length as-of the observed XID.

payload_length_ in hash page slot is mutable, so this must be paired with observed_ in serializable transactions.

Definition at line 86 of file hash_record_location.hpp.

Referenced by foedus::storage::hash::HashStoragePimpl::get_record(), foedus::storage::hash::HashStoragePimpl::get_record_part(), foedus::storage::hash::HashStoragePimpl::increment_record(), foedus::storage::hash::HashStoragePimpl::overwrite_record(), populate_logical(), populate_physical(), and foedus::storage::hash::HashStoragePimpl::upsert_record().

DataPageSlotIndex foedus::storage::hash::RecordLocation::index_

Index of the record in the page.

kSlotNotFound if not found.

Definition at line 80 of file hash_record_location.hpp.

Referenced by foedus::storage::hash::HashStoragePimpl::insert_record(), populate_logical(), populate_physical(), foedus::storage::hash::HashStoragePimpl::register_record_write_log(), and foedus::storage::hash::HashStoragePimpl::upsert_record().

uint16_t foedus::storage::hash::RecordLocation::key_length_

Key length of the slot, which is immutable.

Definition at line 88 of file hash_record_location.hpp.

Referenced by populate_logical(), and populate_physical().

xct::XctId foedus::storage::hash::RecordLocation::observed_

TID as of locate_record() identifying the record.

guaranteed to be not is_moved (then automatically retried), though the current TID might be now moved, in which case pre-commit will catch it. See the class comment.

Definition at line 100 of file hash_record_location.hpp.

Referenced by foedus::storage::hash::HashStoragePimpl::delete_record(), foedus::storage::hash::HashStoragePimpl::increment_record(), foedus::storage::hash::HashStoragePimpl::insert_record(), foedus::storage::hash::HashStoragePimpl::locate_record(), foedus::storage::hash::HashStoragePimpl::locate_record_in_snapshot(), foedus::storage::hash::HashStoragePimpl::overwrite_record(), populate_logical(), populate_physical(), and foedus::storage::hash::HashStoragePimpl::upsert_record().

HashDataPage* foedus::storage::hash::RecordLocation::page_

The data page (might not be bin-head) containing the record.

Definition at line 78 of file hash_record_location.hpp.

Referenced by foedus::storage::hash::HashStoragePimpl::insert_record(), populate_logical(), populate_physical(), foedus::storage::hash::HashStoragePimpl::register_record_write_log(), and foedus::storage::hash::HashStoragePimpl::upsert_record().

uint16_t foedus::storage::hash::RecordLocation::physical_record_length_

Byte count the record of the slot occupies, which is immutable.

Definition at line 90 of file hash_record_location.hpp.

Referenced by populate_logical(), and populate_physical().

xct::ReadXctAccess* foedus::storage::hash::RecordLocation::readset_

If this method took a read-set on the returned record, points to the corresponding read-set.

Otherwise nullptr.

Definition at line 106 of file hash_record_location.hpp.

Referenced by populate_logical(), populate_physical(), and foedus::storage::hash::HashStoragePimpl::register_record_write_log().

char* foedus::storage::hash::RecordLocation::record_

Address of the record.

null if not found.

Definition at line 93 of file hash_record_location.hpp.

Referenced by foedus::storage::hash::HashStoragePimpl::get_record(), foedus::storage::hash::HashStoragePimpl::get_record_part(), foedus::storage::hash::HashStoragePimpl::increment_record(), foedus::storage::hash::HashStoragePimpl::insert_record(), populate_logical(), populate_physical(), foedus::storage::hash::HashStoragePimpl::register_record_write_log(), and foedus::storage::hash::HashStoragePimpl::upsert_record().

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