Data Types

MekaDB is a SQL database. Below is a list of data types supported or planned.

Character Types

SQL DataType
CHAR
VARCHAR
TEXT
STRING

Numeric Types

SQL DataType
TINYINT
SMALLINT
INT or INTEGER
BIGINT
TINYINT UNSIGNED
SMALLINT UNSIGNED
INT UNSIGNED or INTEGER UNSIGNED
BIGINT UNSIGNED
FLOAT
REAL
DOUBLE

Date/Time Types

SQL DataType
TIMESTAMP

Boolean Types

SQL DataType
BOOLEAN

Binary Types

SQL DataType
BYTEA

You can create binary literals using a hex string literal such as X'1234 to create a Binary value of two bytes, 0x12 and 0x34.

Unsupported SQL Types

SQL Data Type	Arrow DataType
UUID	Not yet supported
BLOB	Not yet supported
CLOB	Not yet supported
BINARY	Not yet supported
VARBINARY	Not yet supported
REGCLASS	Not yet supported
NVARCHAR	Not yet supported
CUSTOM	Not yet supported
ARRAY	Not yet supported
ENUM	Not yet supported
SET	Not yet supported
DATETIME	Not yet supported

Supported Arrow Types

MekaDB's SQL capability is built on top of Datafusion. As a result, its arrow_typeof function is also available. The following types are supported by the arrow_typeof function:

Arrow Type
Null
Boolean
Int8
Int16
Int32
Int64
UInt8
UInt16
UInt32
UInt64
Float16
Float32
Float64
Utf8
LargeUtf8
Binary
Timestamp(Second, None)
Timestamp(Millisecond, None)
Timestamp(Microsecond, None)
Timestamp(Nanosecond, None)
Time32
Time64
Duration(Second)
Duration(Millisecond)
Duration(Microsecond)
Duration(Nanosecond)
Interval(YearMonth)
Interval(DayTime)
Interval(MonthDayNano)
FixedSizeBinary(<len>) (e.g. FixedSizeBinary(16))
Decimal128(<precision>, <scale>) e.g. Decimal128(3, 10)
Decimal256(<precision>, <scale>) e.g. Decimal256(3, 10)

MekaDB uses Arrow, and thus the Arrow type system, for query execution. The SQL types from sqlparser-rs are mapped to Arrow data types according to the following table.

This mapping occurs when defining the schema in a CREATE EXTERNAL TABLE command or when performing a SQL CAST operation.

You can see the corresponding Arrow type for any SQL expression using the arrow_typeof function. For example:

❯ select arrow_typeof(interval '1 month');
+-------------------------------------+
| arrowtypeof(IntervalYearMonth("1")) |
+-------------------------------------+
| Interval(YearMonth)                 |
+-------------------------------------+

You can cast a SQL expression to a specific Arrow type using the arrow_cast function For example, to cast the output of now() to a Timestamp with second precision:

❯ select arrow_cast(now(), 'Timestamp(Second, None)');
+---------------------+
| now()               |
+---------------------+
| 2023-03-03T17:19:21 |
+---------------------+

note

Large portions of this page is copied from the Apache Datafusion documentation on January 26th 2024 - where there have been customisations to match Hypi's deployment this has been noted. Apache Datafusion and the Apache name are the property of the Apache Foundation and licensed under the Apache V2 license .