Data Types

This chapter describes the list of data types

Genji provides a list of simple data types to store and manipulate data.

Name Description From To
BOOL Can be either true or false false true
INTEGER Signed integer which takes 1, 2, 4 or 8 bytes depending on the size of the stored number -9223372036854775808 9223372036854775807
DOUBLE 8 bytes decimal -1.7976931348623157e+308 1.7976931348623157e+308
BLOB Variable size BLOB of data
TEXT Variable size UTF-8 encoded string
ARRAY ARRAY of values of any type
DOCUMENT Object that contains pairs that associate a string field to a value of any type

The case of NULL

In Genji, NULL is treated as both a value and a type. It represents the absence of data, and is returned in various cases:

  • when selecting a field that doesn’t exists
  • when selecting a field whose value is NULL
  • as the result of the evaluation of an expression

Conversion

Whenever Genji needs to manipulate data of different types, depending on the situation it will rely on either:

  • explicit conversion: The source type and destination type are clearly identified. Ex: When inserting data to field with a constraint or when doing a CAST.
  • implicit conversion: Two values of different types need to be compared or used by an operator during the evaluation of an expression

Explicit conversion

Explicit conversion is used when we want to convert a value of a source type into a target type. However, Genji types are not all compatible with one another, and when a user tries to convert them, Genji returns an error. Here is a table describing type compatibility.

Source type Target type Converted Example
BOOL INTEGER yes, 1 if true, otherwise 0 CAST(true AS INTEGER) -> 1
BOOL TEXT yes, 'true' if true, otherwise 'false' CAST(true AS TEXT) -> 'true'
INTEGER BOOL yes, false if zero, otherwise true CAST(10 AS BOOL) -> true
INTEGER DOUBLE yes CAST(10 AS DOUBLE) -> 10.0
INTEGER TEXT yes CAST(10 AS TEXT) -> '10'
DOUBLE INTEGER yes, cuts off the decimal part CAST(10.5 AS DOUBLE) -> 10
DOUBLE TEXT yes CAST(10.5 AS DOUBLE) -> '10.5'
TEXT BOOL yes, if the content is a valid boolean CAST('true' AS BOOL) -> true
TEXT INTEGER yes, if the content is a valid integer CAST('10' AS INTEGER) -> 10
TEXT DOUBLE yes, if the content is a valid decimal number CAST('10.4' AS DOUBLE) -> 10.4
TEXT BLOB yes, if the content is a valid base64 value CAST('aGVsbG8K' AS BLOB) -> 'aGVsbG8K'
TEXT ARRAY yes, if the content is a valid json array CAST('[1, 2, 3]' AS ARRAY) -> [1, 2, 3]
TEXT DOCUMENT yes, if the content is a valid json object CAST('{"a": 1}' AS DOCUMENT) -> {"a": 1}
BLOB TEXT yes, the content will be encoded in base64
ARRAY TEXT yes, the content will be encoded as a json array CAST([1, 2, 3] AS TEXT) -> '[1, 2, 3]'
DOCUMENT TEXT yes, the content will be encoded as a json object CAST({a: 1} AS DOUBLE) -> '{"a": 1}'
NULL any type yes, NULL CAST(NULL AS DOUBLE) -> NULL

Implicit conversion

There is only one kind of implicit conversion: INTEGER to DOUBLE. This usually takes place during the evaluation of an expression involving INTEGER and DOUBLE values. No other conversion is applied unless it’s explicit.


Last modified September 29, 2020: Remove duration type (05cd01c)