fluidb/docs/datatypes.md

Value-types

A runtime value in Cozo can be of the following value-types:

• Null
• Bool
• Number
• String
• Bytes
• List

Number can be Float (double precision) or Int (signed, 64 bits). Cozo will auto-promote Int to Float when necessary.

List can contain any number of mixed-type values, including other lists.

Cozo sorts values according to the above order, e.g. null is smaller than true, which is in turn smaller than the list [].

Within each type values are compared according to logic custom to each type:

• false < true;
• -1 == -1.0 < 0 == 0.0 < 0.5 == 0.5 < 1 == 1.0 (however, see the caveat below);
• Lists are ordered lexicographically by their elements;
• Bytes are compared lexicographically;
• Strings are ordered lexicographically by their UTF-8 byte representations.

!> Because there are two internal number types Int and Float under the umbrella type Number, sorting numbers can be more complex than anticipated: when sorting, the integer always comes before the equivalent float. For example, 1.0 == 1, 1.0 >= 1 and 1.0 <= 1 all evaluate to true, but when sorting 1 and 1.0 are two different values and 1 is placed before 1.0. This may create problems when applying aggregations since if a grouping key contains both 1.0 and 1, they are treated as separate group headings. In such cases, it may help to use explicit coercion to_float or round to coerce all sorted values to the same type.

Value literals

null for the type Null, false and true for the type Bool are standard.

Numbers ...

Strings ...

There is no literal representation for Bytes due to restrictions placed by JSON. But ...

Lists ...

Schema-types

In schema definition, the required type for a value can be specified by any of the following schema-types

• Ref
• Component
• Int
• Float
• Bool
• String
• Bytes
• List

When retrieving triples' values, the schema-types Ref, Component, and Int are all represented by the value-type Number (actually Int). The entity (the subject of the triple) is always a Ref, always represented by a Number (Int).

Note the absence of the Null type in schema-types.

When asserting (inserting or updating) triples, if a value given is not of the correct schema-type, Cozo will first try to coerce the value and will only error out if no known coercion methods exist.