Type matrix

What Migrate and PlanMigration generate for each Go type, on each engine.

This page is generated from the type mapper itself, so it cannot drift from what the code does. A hand-written version was wrong about integer widths for as long as it existed.

Go type	PostgreSQL	MySQL	MariaDB	SQLite	SQL Server	Oracle
string	TEXT	VARCHAR(255)	VARCHAR(255)	TEXT	NVARCHAR(255)	VARCHAR2(255)
string with size=255	VARCHAR(255)	VARCHAR(255)	VARCHAR(255)	VARCHAR(255)	NVARCHAR(255)	VARCHAR2(255)
bool	BOOLEAN	BOOLEAN	BOOLEAN	BOOLEAN	BIT	NUMBER(1)
int8 / int16	SMALLINT	SMALLINT	SMALLINT	SMALLINT	SMALLINT	NUMBER(5)
int32	INTEGER	INTEGER	INTEGER	INTEGER	INTEGER	NUMBER(10)
int / int64	BIGINT	BIGINT	BIGINT	BIGINT	BIGINT	NUMBER(19)
uint64	BIGINT	BIGINT	BIGINT	BIGINT	BIGINT	NUMBER(19)
float32	REAL	REAL	REAL	REAL	REAL	BINARY_FLOAT
float64	DOUBLE PRECISION	DOUBLE	DOUBLE	REAL	FLOAT(53)	BINARY_DOUBLE
float64 with precision=18,scale=4	DECIMAL(18,4)	DECIMAL(18,4)	DECIMAL(18,4)	DECIMAL(18,4)	DECIMAL(18,4)	DECIMAL(18,4)
time.Time	TIMESTAMP	DATETIME	DATETIME	DATETIME	DATETIME2	TIMESTAMP
[]byte	BYTEA	BLOB	BLOB	BLOB	VARBINARY(MAX)	BLOB
time.Duration	BIGINT	BIGINT	BIGINT	BIGINT	BIGINT	NUMBER(19)
integer primary key	BIGSERIAL PRIMARY KEY	BIGINT AUTO_INCREMENT PRIMARY KEY	BIGINT AUTO_INCREMENT PRIMARY KEY	INTEGER PRIMARY KEY AUTOINCREMENT	BIGINT IDENTITY(1,1) PRIMARY KEY	NUMBER GENERATED ALWAYS AS IDENTITY PRIMARY KEY
string primary key	VARCHAR(36) PRIMARY KEY	VARCHAR(36) PRIMARY KEY	VARCHAR(36) PRIMARY KEY	VARCHAR(36) PRIMARY KEY	NVARCHAR(36) PRIMARY KEY	VARCHAR2(36) PRIMARY KEY
[]string, []int64, map[string]any	TEXT	TEXT	TEXT	TEXT	TEXT	TEXT

Notes

• int / int64 — Go's int is 64-bit on every supported platform.
• uint64 — Stored signed; values above 2⁶³−1 do not fit.
• float64 with precision=18,scale=4 — Use this for money: binary floats cannot represent every decimal.
• time.Duration — Stored as an integer count of nanoseconds.
• integer primary key — Auto-increment.
• string primary key — For UUID/ULID keys the caller supplies.
• []string, []int64, map[string]any — Serialised as text; no native array or JSONB column yet.

Integer width

Integers map by the width of the Go type. They used to collapse onto a single INTEGER, which is four bytes on PostgreSQL, MySQL and SQL Server: an int64 past 2³¹ was rejected by those engines while looking fine on SQLite, whose INTEGER is dynamically sized. Auto-increment keys were narrow for the same reason and ran out at 2,147,483,647 rows.

If you have tables created before this changed, PlanMigration reports the widening as an ALTER COLUMN. Applying it is safe — widening loses no data — but on a large table the engine may rewrite it, so run it when a rewrite is acceptable rather than at deploy time.

Floating point

REAL is single precision on PostgreSQL: about seven significant digits, where a float64 carries fifteen. SQLite's REAL is an 8-byte IEEE double and was never affected.

For money, use precision and scale and get a DECIMAL: no binary float represents every decimal fraction exactly.