MariaDB type mapping

The tables below list every MariaDB column type (MariaDB Data Types) and the Kotlin type produced when the column is read into a DataFrame. MariaDB canonicalizes aliases at CREATE TABLE time, so DataFrame only ever sees the canonical type; they are listed in the same row as the canonical type for reference.

Column nullability is determined from the metadata provided by the JDBC driver. If the driver does not explicitly report a column as non-nullable, it is mapped to a nullable Kotlin type (Int? instead of Int).

Numeric types

Canonical	Aliases	DataFrame column type	Notes
`TINYINT[(M)]`	`INT1`	`Int`	1-byte signed integer (`-128 .. 127`).
`TINYINT UNSIGNED`	`INT1 UNSIGNED`	`Int`	1-byte unsigned integer (`0 .. 255`).
`BOOL`, `BOOLEAN`	alias for `TINYINT(1)`	`Boolean`	Stored as `TINYINT(1)`; values are `0`/`1`.
`SMALLINT[(M)]`	`INT2`	`Int`	2-byte signed integer. Becomes `Short` if the driver reports the column class as `java.lang.Short`.
`SMALLINT UNSIGNED`	`INT2 UNSIGNED`	`Int`	2-byte unsigned integer.
`MEDIUMINT[(M)]`	`INT3`, `MIDDLEINT`	`Int`	3-byte signed integer.
`MEDIUMINT UNSIGNED`	`INT3 UNSIGNED`, `MIDDLEINT UNSIGNED`	`Int`	3-byte unsigned integer.
`INT[(M)]`	`INTEGER`, `INT4`	`Int`	4-byte signed integer.
`INT UNSIGNED`	`INTEGER UNSIGNED`, `INT4 UNSIGNED`	`Long`	MariaDB override: fits in `Long`, not `Int`.
`BIGINT[(M)]`	`INT8`	`Long`	8-byte signed integer.
`BIGINT UNSIGNED`	`INT8 UNSIGNED`	`java.math.BigInteger`	MariaDB override: exceeds `Long`, needs `BigInteger`.
`DECIMAL(M,D)`	`DEC`, `NUMERIC`, `FIXED`	`java.math.BigDecimal`	Fixed-point.
`FLOAT[(P)]`	`FLOAT4`	`Float`	4-byte float. Becomes `Double` if the driver reports the column class as `java.lang.Double`.
`DOUBLE`	`FLOAT8`, `DOUBLE PRECISION`, `REAL`	`Double`	8-byte float.
`BIT(M)`	none	`ByteArray`	Reported as `VARBINARY` for `M > 1`; `BIT(1)` may map to `Boolean`.

Date and time types

Canonical	Aliases	DataFrame column type	Notes
`DATE`	none	`java.util.Date`
`TIME[(fsp)]`	none	`java.sql.Time`	`fsp` is fractional seconds precision (0–6).
`DATETIME[(fsp)]`	none	`kotlin.time.Instant`	Preprocessed from `java.sql.Timestamp`.
`TIMESTAMP[(fsp)]`	none	`kotlin.time.Instant`	Preprocessed from `java.sql.Timestamp`.
`YEAR[(4)]`	none	`java.util.Date`	1-byte year (`1901..2155`); driver reports it as `Types.DATE`.

String types

Canonical	Aliases	DataFrame column type	Notes
`CHAR(M)`	`CHARACTER(M)`, `NATIONAL CHAR(M)`, `NCHAR(M)`	`String`	Fixed-length text. Max `M = 255`.
`VARCHAR(M)`	`CHARACTER VARYING(M)`, `NATIONAL VARCHAR(M)`, `NVARCHAR(M)`	`String`	Variable-length text.
`BINARY(M)`	none	`ByteArray`	Fixed-length binary.
`VARBINARY(M)`	`BINARY VARYING(M)`	`ByteArray`	Variable-length binary.
`TINYBLOB`	none	`ByteArray`	Up to 255 bytes.
`TINYTEXT`	none	`String`	Up to 255 bytes.
`BLOB[(M)]`	none	`ByteArray`	Up to 64 KiB.
`TEXT[(M)]`	none	`String`	Up to 64 KiB.
`MEDIUMBLOB`	`LONG VARBINARY`	`ByteArray`	Up to 16 MiB.
`MEDIUMTEXT`	`LONG VARCHAR`, `LONG`	`String`	Up to 16 MiB.
`LONGBLOB`	none	`ByteArray`	Up to 4 GiB.
`LONGTEXT`	none	`String`	Up to 4 GiB.
`ENUM(...)`	none	`String`	Enumeration; values read as their string form.
`SET(...)`	none	`String`	Comma-separated set of values, as a single string.

JSON and UUID

Canonical	Aliases	DataFrame column type	Notes
`JSON`	none	`String`	Physically stored as `LONGTEXT` in MariaDB; JDBC reports `LONGVARCHAR` → `String`.
`UUID`	none	`String`	Available in MariaDB 10.7+. Read as text. Use `parse` to get `kotlin.uuid.Uuid`.
`INET4`	none	`String`	Available in MariaDB 10.10+.
`INET6`	none	`String`	Available in MariaDB 10.10+.
`ROW(...)`	none	unsupported	Anonymous row types are not currently mapped; see Unsupported types.

Spatial types

All spatial types are read as ByteArray (WKB / EWKB binary as reported by the driver).

Canonical	Aliases	DataFrame column type
`GEOMETRY`	none	`ByteArray`
`POINT`	none	`ByteArray`
`LINESTRING`	none	`ByteArray`
`POLYGON`	none	`ByteArray`
`MULTIPOINT`	none	`ByteArray`
`MULTILINESTRING`	none	`ByteArray`
`MULTIPOLYGON`	none	`ByteArray`
`GEOMETRYCOLLECTION`	none	`ByteArray`

MariaDB specifics

INT UNSIGNED/INTEGER UNSIGNED and BIGINT UNSIGNED are the only types that need MariaDB-specific handling. INT UNSIGNED is widened to Long and BIGINT UNSIGNED becomes BigInteger because its range exceeds Long.
SMALLINT may become Short (rather than Int) when the JDBC driver reports the column class as java.lang.Short.
BIT(1) and BOOLEAN are stored the same way (as TINYINT(1)) — see MariaDB's BOOLEAN and BIT pages. Which Kotlin type surfaces depends on how the driver reports the column's jdbcType and javaClassName.
Display width (INT(11)) and ZEROFILL are server-side metadata and are not surfaced by the MariaDB JDBC driver in getColumnTypeName(); DataFrame only ever sees the canonical name — see Numeric Data Type Overview.

Unsupported types

Anonymous ROW(...) types; read as String.
VECTOR (MariaDB 11.7+); read as ByteArray (raw binary storage).
Native representations of spatial types; read as raw WKB ByteArray.

09 September 2026