H2 type mapping

The tables below list every H2 column type (H2 Data Types) and the Kotlin type produced when the column is read into a DataFrame in H2.Mode.Regular. Aliases are canonicalized by H2 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.

For non-Regular modes, H2 delegates to the emulated dialect — see the Mode section below.

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).

Character types

Canonical	Aliases	DataFrame column type	Notes
`CHAR[(n)]`	`CHARACTER`, `NCHAR`	`String`	Fixed-length text.
`VARCHAR[(n)]`	`CHARACTER VARYING`, `LONGVARCHAR`, `VARCHAR2`, `NVARCHAR`, `NVARCHAR2`, `VARCHAR_CASESENSITIVE`	`String`	Variable-length text.
`VARCHAR_IGNORECASE[(n)]`	none	`String`	Case-insensitive comparison; stored as text.
`CLOB`	`CHARACTER LARGE OBJECT`, `TINYTEXT`, `TEXT`, `MEDIUMTEXT`, `LONGTEXT`, `NTEXT`, `NCLOB`	`java.sql.Clob`	Large text object.

Binary types

Canonical	Aliases	DataFrame column type	Notes
`BINARY[(n)]`	`RAW`	`ByteArray`	Fixed-length binary.
`VARBINARY[(n)]`	`LONGVARBINARY`, `BINARY VARYING`	`ByteArray`	Variable-length binary.
`BLOB`	`BINARY LARGE OBJECT`, `TINYBLOB`, `MEDIUMBLOB`, `LONGBLOB`, `IMAGE`	`java.sql.Blob`	Large binary object.

Boolean

Canonical	Aliases	DataFrame column type	Notes
`BOOLEAN`	`BOOL`, `BIT`, `LOGICAL`	`Boolean`	Single-bit boolean.

Numeric types

Canonical	Aliases	DataFrame column type	Notes
`TINYINT`	none	`Int`	1-byte signed integer.
`SMALLINT`	`INT2`, `YEAR`	`Int`	2-byte signed integer.
`INTEGER`	`INT`, `INT4`, `MEDIUMINT`, `SIGNED`	`Int`	4-byte signed integer.
`BIGINT`	`INT8`	`Long`	8-byte signed integer.
`NUMERIC[(p[,s])]`	`DECIMAL[(p[,s])]`, `DEC[(p[,s])]`, `NUMBER[(p[,s])]`	`java.math.BigDecimal`	Fixed-point.
`REAL`	`FLOAT4`	`Float`	4-byte float.
`DOUBLE PRECISION`	`DOUBLE`, `FLOAT`, `FLOAT8`	`Double`	8-byte float.
`DECFLOAT[(p)]`	none	`java.math.BigDecimal`	Decimal floating-point (H2 2.0+).

Date and time types

Canonical	Aliases	DataFrame column type	Notes
`DATE`	none	`java.util.Date`
`TIME[(p)] [WITHOUT TIME ZONE]`	none	`java.sql.Time`
`TIME[(p)] WITH TIME ZONE`	none	`java.time.OffsetTime`
`TIMESTAMP[(p)] [WITHOUT TIME ZONE]`	`DATETIME`, `SMALLDATETIME`	`kotlin.time.Instant`	Preprocessed from `java.sql.Timestamp`.
`TIMESTAMP[(p)] WITH TIME ZONE`	`DATETIMEOFFSET`, `TIMESTAMPTZ`	`java.time.OffsetDateTime`
`INTERVAL YEAR[(p)]`, `INTERVAL MONTH[(p)]`, ...	none	`String` (unsupported	Any of the 13 interval subtypes; read as text.

Other types

Canonical	Aliases	DataFrame column type	Notes
`UUID`	none	`kotlin.uuid.Uuid`	Preprocessed from `java.util.UUID`. Driver reports `Types.BINARY` + `java.util.UUID` class.
`JAVA_OBJECT`	`OTHER`	`Any`	Serialised Java object; read as opaque `Any`.
`ENUM`	none	`String`	User-declared enum labels.
`GEOMETRY`	none	`String` (unsupported)	Only WKT text.
`JSON`	none	`String`	JSON text.
`ARRAY`	none	`Array<*>`	Element type inferred; falls back to `Any` for heterogeneous arrays.
`ROW(...)`	none	`String` (unsupported)

Unsupported types

ROW(...) composite / structured types; driver reports Types.OTHER; DataFrame column type is Any.
INTERVAL subtypes (all 13); read as their text form to a String column.
Domain types (H2 supports CREATE DOMAIN); transparent at the JDBC layer — the underlying primitive's mapping applies with a column of the corresponding type.
GEOMETRY in binary/WKB form; DataFrame reads only the WKT text form to a String column.

H2 modes

H2(mode = ...) selects the dialect H2 emulates and delegates its type mapping to that dialect. The default mode is Regular.

Mode	Delegates to
`Regular`	Default H2 mapping (this page)
`MySql`	MySQL
`PostgreSql`	PostgreSQL
`MsSqlServer`	MS SQL
`MariaDb`	MariaDB

09 September 2026