Module row_rule 

The values a compiled row rule computes with, and its operators.

The schema generator compiles each row rule a module declares (a condition over one row’s own fields) into a Rust expression over Val, built from the functions here, and evaluates it against the row the write would store, read through the row’s JSON form so enums, decimals and dates arrive as the text and numbers their columns hold.

The semantics are SQL’s, because the same rule also compiles to a CHECK constraint and both must give one answer:

• A missing or null field is Val::Null, and an operator over a null is null: name.length >= 1 with no name is neither true nor false.
• &&, || and ! are three-valued: false && null is false, true || null is true, anything else with a null is null.
• A rule holds unless it is definitely false, as a CHECK passes on null. x == null and x != null test for null itself and are never null.
• A comparison between a number and a text parses the text, the way a decimal column serialized as "12.50" compares to 0; a comparison between a time and a text parses the text as a timestamp or a date.

A rule may also read the row before the write ($old.x, through field on that row), the writer (actor) and the time of the write (at).

Enums

Val

One value inside a rule.

Functions

abs

actor

The writer, as $actor.id reads it; null for a job, a seed or an unscoped caller.

add

and

at

The time of the write, as now() reads it.

ceil

changed

Whether any of fields differs between the row before and the row after a write. A rule about the time of the write checks an update only when it changes what the rule reads, so a later edit of a row whose deadline has passed is not a break.

coalesce

The first value that is not null.

cond

c ? t : e, as SQL’s CASE WHEN c THEN t ELSE e END: a null condition takes e.

contains

a.contains(b): a text containing a text, or a list containing an item.

div

Division by zero is null rather than an error: a rule never panics a write.

ends_with

eq

field

The row’s field name; Val::Null when it is absent or null.

floor

ge

gt

has_role

$actor.has_role(role): null without a writer, without an installed roles source (crate::actor_roles), or when the source cannot tell; the rule then holds.

holds

Whether a rule’s value lets the write through: everything but a definite false.

in_list

a in [..], as SQL’s IN: true on a match, null when a is null or no item matched but one was null, false otherwise.

is_empty

is_not_null

is_null

le

length

A text’s length in characters (code points, as on every target), or a list’s.

lower

lt

matches

a matches 'pattern': whether the text contains a match of the pattern. The generator only emits patterns that compile.

mul

ne

neg

not

not_in

or

referencing

How many rows still reference the row being deleted: sql counts them with the row’s id as $1, run on the request’s own connection. Null outside a request or without an id.

rem

round

starts_with

sub

text

trim

upper