Module types 

Encode, Decode and Type for the Rust types D1 can store.

D1 is SQLite behind a JavaScript API, so the mapping follows sqlx-sqlite wherever D1 does not force a difference – code moving from Sqlite to D1 should behave the same. Where it does force one, it fails loudly:

Rust	Stored as	Notes
bool	INTEGER 0/1	any non-zero integer decodes as true
i8, i16, i32, u8, u16, u32	INTEGER	decoding a value that does not fit is an error
i64	INTEGER	only within ±(2^53 − 1), in both directions
f32, f64	REAL	also decode from INTEGER
&str, String, Box<str>, Arc<str>, Cow<str>	TEXT
&[u8], Vec<u8>, Box<[u8]>, Arc<[u8]>	BLOB	also decode from TEXT, as its bytes

u64 is deliberately missing: there is nothing it could be stored as without losing most of its range.

Integers and JavaScript numbers

D1 passes values as JavaScript numbers, never BigInt, and a number is exact only up to 2^53 − 1. So binding an i64 outside ±(2^53 − 1) is an error, not a value rounded on the way in, and a stored integer beyond that range comes back as a REAL that will not decode as i64.

For the same reason, a whole number stored as REAL – 3.0 – arrives indistinguishable from the integer 3, and is typed INTEGER. That is why the float types decode from INTEGER too.