SQLite 3 cells

A cell is one entry on a b-tree page: a row, an index entry, or a divider that points to a child page. The page type decides which of four layouts its cells use. Numbers marked varint use SQLite’s variable-length integers; the others are big-endian.

The four layouts

Part, in order	Table leaf (13)	Table interior (5)	Index leaf (10)	Index interior (2)
Left child page, u32	–	yes	–	yes
Payload size, varint: all of it, overflow included	yes	–	yes	yes
Rowid, varint	yes	yes (the key)	–	–
Payload: the part that stays on the page	yes	–	yes	yes
First overflow page, u32: only if the payload spills	yes	–	yes	yes

The payload is a record. How much of it stays on the page, and when the rest goes to overflow pages, is set by the overflow thresholds. A reader learns whether a cell spills by comparing its payload size with them: no flag in the cell says so.

Table leaf cells

A row of a table: its rowid and its record.

Size	Type	Name	Description
1 to 9	varint	Payload size	The size of the record in bytes, including any part on overflow pages.
1 to 9	varint	Rowid	The row’s 64-bit signed integer key.
varies	bytes	Payload	The record, or its first part if it spills.
0 or 4	u32	First overflow page	Present only when the payload spills.

Table interior cells

A divider. The left child page holds the rows whose rowids are less than or equal to this cell’s key; the next cell’s left child, or the page’s right-most pointer after the last cell, holds the larger ones. There is no payload, so these cells never spill.

Size	Type	Name	Description
4	u32	Left child page	The child page with the keys up to and including this one.
1 to 9	varint	Key	A rowid: every row under the left child has a rowid up to and including it.

Index leaf cells

An index entry: a record of the indexed values followed by the row’s key, the rowid or, for a WITHOUT ROWID table, its PRIMARY KEY columns. See Indexes.

Size	Type	Name	Description
1 to 9	varint	Payload size	The size of the record in bytes, including any part on overflow pages.
varies	bytes	Payload	The record, or its first part if it spills.
0 or 4	u32	First overflow page	Present only when the payload spills.

Index interior cells

An index entry that also points to the child page holding the smaller entries. In an index b-tree every entry appears exactly once, on a leaf page or on an interior page. Read in order, a child’s entries come before the interior cell that points to it, and the entries under the right-most pointer come after the last cell.

Size	Type	Name	Description
4	u32	Left child page	The child page with the entries before this one.
1 to 9	varint	Payload size	The size of the record in bytes, including any part on overflow pages.
varies	bytes	Payload	The record, or its first part if it spills.
0 or 4	u32	First overflow page	Present only when the payload spills.

A real cell

A table leaf cell from the files examined for this site, a row of a link table made as (id INTEGER PRIMARY KEY, author, paper):

06 21 04 00 01 01 1B 0A

An 8-byte table leaf cell: the payload size and rowid are marked

06: a payload of 6 bytes. 21: rowid 33.
The payload is the record: 04, a record header of 4 bytes; serial types 00 (NULL), 01 and 01 (8-bit integers).
The values: NULL, then 1B = 27 and 0A = 10.

The id column is an INTEGER PRIMARY KEY, so it is the rowid itself and is stored in the record as NULL. The row reads (33, 27, 10).