mongo::BtreeBucketV0 Struct Reference

This structure represents header data for a btree bucket. More...

#include <btree_ondisk.h>

Detailed Description

This structure represents header data for a btree bucket.

An object of this type is typically allocated inside of a buffer of size BucketSize, resulting in a full bucket with an appropriate header.

The body of a btree bucket contains an array of _KeyNode objects starting from its lowest indexed bytes and growing to higher indexed bytes. The body also contains variable width bson keys, which are allocated from the highest indexed bytes toward lower indexed bytes.

|hhhh|kkkkkkk-----—bbbbbbbbbbbuuubbbuubbb| h = header data k = KeyNode data

• = empty space b = bson key data u = unused (old) bson key data, that may be garbage collected

Public Types
enum	{ HeaderSize = 40 }

Public Attributes
DiskLoc	parent
	Parent bucket of this bucket, which isNull() for the root bucket. More...
DiskLoc	nextChild
	Given that there are n keys, this is the n index child. More...
unsigned short	_wasSize
	Can be reused, value is 8192 in current pdfile version Apr2010. More...
unsigned short	_reserved1
	zero More...
int	flags
int	emptySize
	basicInsert() assumes the next three members are consecutive and in this order: More...
int	topSize
	Size used for bson storage, including storage of old keys. More...
int	n
int	reserved
char	data [4]

Member Enumeration Documentation

anonymous enum

anonymous enum

Enumerator
HeaderSize

Member Data Documentation

_reserved1

unsigned short mongo::BtreeBucketV0::_reserved1

zero

_wasSize

unsigned short mongo::BtreeBucketV0::_wasSize

Can be reused, value is 8192 in current pdfile version Apr2010.

data

char mongo::BtreeBucketV0::data[4]

emptySize

int mongo::BtreeBucketV0::emptySize

basicInsert() assumes the next three members are consecutive and in this order:

Size of the empty region.

flags

int mongo::BtreeBucketV0::flags

n

int mongo::BtreeBucketV0::n

nextChild

DiskLoc mongo::BtreeBucketV0::nextChild

Given that there are n keys, this is the n index child.

parent

DiskLoc mongo::BtreeBucketV0::parent

Parent bucket of this bucket, which isNull() for the root bucket.

reserved

int mongo::BtreeBucketV0::reserved

topSize

int mongo::BtreeBucketV0::topSize

Size used for bson storage, including storage of old keys.

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

• /home/louis/git/mongodbsource.github.io/src/src/mongo/db/storage/mmap_v1/btree/btree_ondisk.h