Module predicate 

Filter predicates evaluated against Value field contents.

Predicate is an enum (rather than a trait) so callers can pattern match on the special IsNull / IsNotNull cases that need to see the None field value, while everything else short-circuits on missing fields. Like / ILike regex variants land alongside the SQL compiler.

Enums

Predicate

Functions

sql_null_test

SQL IS NULL (or IS NOT NULL when negated), as PostgreSQL’s NullTest evaluates it: a row value is null when every field is null and not null when no field is, so a row with both kinds of fields is neither; any other value is null only when it is the null value. An absent field is null.