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BadgerDB
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BadgerDB
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Class which represents a fixed-size database page containing records. More...
#include <page.h>
Public Member Functions | |
| Page () | |
| RecordId | insertRecord (const std::string &record_data) |
| std::string | getRecord (const RecordId &record_id) const |
| void | updateRecord (const RecordId &record_id, const std::string &record_data) |
| void | deleteRecord (const RecordId &record_id) |
| bool | hasSpaceForRecord (const std::string &record_data) const |
| std::uint16_t | getFreeSpace () const |
| PageId | page_number () const |
| PageId | next_page_number () const |
| PageIterator | begin () |
| PageIterator | end () |
Static Public Attributes | |
| static const std::size_t | SIZE = 8192 |
| static const std::size_t | DATA_SIZE = SIZE - sizeof(PageHeader) |
| static const PageId | INVALID_NUMBER = 0 |
| static const SlotId | INVALID_SLOT = 0 |
Friends | |
| class | File |
| class | PageIterator |
| class | PageTest |
| class | BufferTest |
Class which represents a fixed-size database page containing records.
A page is a fixed-size unit of data storage. Each page holds zero or more records, which consist of arbitrary binary data. Records are placed into slots and identified by a RecordId. Although a record's actual contents may be moved on the page, accessing a record by its slot is consistent.
| void badgerdb::Page::deleteRecord | ( | const RecordId & | record_id | ) |
Deletes the record with the given ID. Page is compacted upon delete to ensure that data of all records is contiguous. Slot array is compacted if the slot deleted is at the end of the slot array.
| record_id | ID of the record to delete. |
Definition at line 66 of file page.cpp.
{
deleteRecord(record_id, true /* allow_slot_compaction */);
}
Returns an iterator representing the record after the last record in the page. This iterator should not be dereferenced.
Definition at line 200 of file page.cpp.
{
const RecordId& end_record_id = {page_number(), Page::INVALID_SLOT};
return PageIterator(this, end_record_id);
}
| std::uint16_t badgerdb::Page::getFreeSpace | ( | ) | const [inline] |
Returns this page's free space in bytes.
Definition at line 185 of file page.h.
{ return header_.free_space_upper_bound -
header_.free_space_lower_bound; }
| std::string badgerdb::Page::getRecord | ( | const RecordId & | record_id | ) | const |
Returns the record with the given ID. Returned data is a copy of what is stored on the page; use updateRecord to change it.
| record_id | ID of the record to return. |
Definition at line 43 of file page.cpp.
{
validateRecordId(record_id);
const PageSlot& slot = getSlot(record_id.slot_number);
return data_.substr(slot.item_offset, slot.item_length);
}
| bool badgerdb::Page::hasSpaceForRecord | ( | const std::string & | record_data | ) | const |
Returns true if the page has enough free space to hold the given data.
| record_data | Bytes that compose the record. |
Definition at line 125 of file page.cpp.
{
std::size_t record_size = record_data.length();
if (header_.num_free_slots == 0) {
record_size += sizeof(PageSlot);
}
return record_size <= getFreeSpace();
}
| RecordId badgerdb::Page::insertRecord | ( | const std::string & | record_data | ) |
Inserts a new record into the page.
| record_data | Bytes that compose the record. |
Definition at line 33 of file page.cpp.
{
if (!hasSpaceForRecord(record_data)) {
throw InsufficientSpaceException(
page_number(), record_data.length(), getFreeSpace());
}
const SlotId slot_number = getAvailableSlot();
insertRecordInSlot(slot_number, record_data);
return {page_number(), slot_number};
}
| PageId badgerdb::Page::next_page_number | ( | ) | const [inline] |
Returns the number of the next used page this page in its file.
Definition at line 200 of file page.h.
{ return header_.next_page_number; }
| PageId badgerdb::Page::page_number | ( | ) | const [inline] |
Returns this page's number in its file.
Definition at line 193 of file page.h.
{ return header_.current_page_number; }
| void badgerdb::Page::updateRecord | ( | const RecordId & | record_id, |
| const std::string & | record_data | ||
| ) |
Updates the record with the given ID, replacing its data with a new version. This is equivalent to deleting the old record and inserting a new one, with the exception that the record ID will not change.
| record_id | ID of record to update. |
| record_data | Updated bytes that compose the record. |
Definition at line 49 of file page.cpp.
{
validateRecordId(record_id);
const PageSlot* slot = getSlot(record_id.slot_number);
const std::size_t free_space_after_delete =
getFreeSpace() + slot->item_length;
if (record_data.length() > free_space_after_delete) {
throw InsufficientSpaceException(
page_number(), record_data.length(), free_space_after_delete);
}
// We have to disallow slot compaction here because we're going to place the
// record data in the same slot, and compaction might delete the slot if we
// permit it.
deleteRecord(record_id, false /* allow_slot_compaction */);
insertRecordInSlot(record_id.slot_number, record_data);
}
const std::size_t badgerdb::Page::DATA_SIZE = SIZE - sizeof(PageHeader) [static] |
const PageId badgerdb::Page::INVALID_NUMBER = 0 [static] |
const SlotId badgerdb::Page::INVALID_SLOT = 0 [static] |
const std::size_t badgerdb::Page::SIZE = 8192 [static] |
1.7.6.1