# `Lotus.UnsupportedOperatorError`
[🔗](https://github.com/elixir-lotus/lotus/blob/v1.0.0/lib/lotus/unsupported_operator_error.ex#L1)

Raised when a caller attempts to apply a `Lotus.Query.Filter` operator
that the adapter has not declared as supported via
`supported_filter_operators/1`.

Rather than silently degrading (substring-match when `:like` is asked
for, or ignoring `:is_null`), Lotus fails loudly so host applications
catch the mismatch early and gate their UI on
`Lotus.Source.supported_filter_operators/1`.

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*Consult [api-reference.md](api-reference.md) for complete listing*