Operators, by profile

All of the listed filters must evaluate TRUE.

At least one of the listed filters must evaluate TRUE.

NOT (a OR b OR …), evaluated under three-valued logic. It is TRUE only when every listed filter is FALSE: if one of them is UNKNOWN the result is UNKNOWN, not TRUE, so a $nor over a nullable field excludes the records whose field is null or absent. See the spec §4.1.

Negates a filter. Under three-valued logic NOT UNKNOWN is UNKNOWN, not TRUE — so this does not match records whose field is null or absent. Add $unknownAs to the inner constraint to include them. See the spec §4.1.

Negates the constraint on this field. {"age": {"$not": {"$gt": 5}}} is TRUE when age is not greater than 5 and UNKNOWN when age is null or absent.

Field equals the operand. Any JSON value, including null, arrays and objects. A value of a different JSON type is unequal — FALSE, not UNKNOWN.

Field does not equal the operand. The negation of $eq under three-valued logic, so this is UNKNOWN — and therefore does not match — when the field is null or absent. Add $unknownAs: true to include those records. See the spec §4.1.

Field equals at least one member of the list. Compares the whole value — it does NOT test membership inside an array-valued field: {"tags": {"$in": ["a"]}} asks whether tags equals "a". For array elements quantify explicitly: {"tags": {"$some": {"$in": ["a"]}}}.

Field equals no member of the list. Like $in, compares the whole value rather than array elements. The negation of $in under three-valued logic, so it is UNKNOWN when the field is null or absent.

Field is strictly greater than the operand.

Field is greater than or equal to the operand.

Field is strictly less than the operand.

Field is less than or equal to the operand.

true if the field is present on the record, even when its value is null; false if absent. Total — never UNKNOWN. Distinct from $isNull — see the spec §4.2.

true if the field's value is null (equivalent to {"$eq": null}); false if it is non-null (equivalent to {"$ne": null}). UNKNOWN only when the path resolves to nothing.

Resolves UNKNOWN to TRUE or FALSE for this constraint, applied last — after every sibling operator, including a field-level $not. {"status": {"$ne": "archived", "$unknownAs": true}} means not archived, and count the records where status is null or absent. A modifier, not a predicate: it needs at least one operator beside it. No-op on $exists, which is already total. See the spec §4.6.

SQL LIKE pattern: % matches any run of characters, _ matches exactly one, and \ escapes either. Case-sensitive.

Negated $like, under three-valued logic: UNKNOWN when the field is null, absent or not a string.

Case-insensitive $like. Collation is server-defined; see the spec §5.5.

Negated $ilike, under three-valued logic: UNKNOWN when the field is null, absent or not a string.

Field begins with this literal substring. Wildcards are not interpreted.

Field ends with this literal substring. Wildcards are not interpreted.

Field contains this literal substring. String-only — for arrays, quantify over the elements with $some or $every.

Field matches this regular expression (ECMA-262 syntax). Servers SHOULD bound execution time; see the spec §7.

Modifiers for $regex: i case-insensitive, m multiline, s dot-matches-newline. Only valid alongside $regex.

Field falls within [lower, upper], inclusive of both bounds.

Field falls outside [lower, upper]. The negation of $between under three-valued logic, so it is UNKNOWN when the field is null or absent.

Fields JSON type. integer' matches a number with no fractional part.

At least one element of the array-valued field satisfies this condition. Supply a Filter for arrays of objects (paths are relative to the element) or a constraint object for arrays of scalars. An element for which the condition is UNKNOWN does not satisfy it, so the quantifier yields TRUE or FALSE over any array — FALSE for an empty one. It is UNKNOWN only when the field is not an array, including when it is null or absent. See the spec §5.8.

Every element of the array-valued field satisfies this condition; an element for which it is UNKNOWN does not. TRUE for an empty array, vacuously. UNKNOWN only when the field is not an array, including when it is null or absent — a missing array is not vacuously TRUE. Same operand shape as $some. See the spec §5.8.

The array-valued field contains every member of this list. Quantifies over the operand rather than over the elements, which is why it is not expressible as a $some or $every. Set semantics: multiplicity is ignored. UNKNOWN when the field is not an array.

Length of the array-valued field: either an exact count or a nested numeric constraint.

Compares against another field of the same record rather than a constant: {"price": {"$gt": {"$field": "cost"}}} is SQL's WHERE price > cost.

Forces the wrapped value to be treated as data. Required only when an object operand would otherwise look like a field reference, e.g. {"$literal": {"$field": "not-a-reference"}}.

Free-text match against the field. Tokenisation, stemming and relevance are server-defined.