docs/source/contributor-guide/expression-audits/map_funcs.md

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# map_funcs Expression Audits

> Audit notes for expressions in this category that have been audited. Absence of an entry means the expression has not been audited yet, not that it is unsupported. See the user guide [Spark Expression Support] for current support status.

## element_at

- Spark 3.4.3 (audited 2026-05-27): identical to 3.5.8.
- Spark 3.5.8 (audited 2026-05-27): baseline. `ElementAt(left, right, defaultValueOutOfBound, failOnError) extends GetMapValueUtil`; the parser routes `element_at(<array>, ...)` to one overload and `element_at(<map>, ...)` to another. Comet routes `MapType` input through the same native `map_extract` path used by `GetMapValue`.
- Spark 4.0.1 (audited 2026-05-27): adds `nullIntolerant: Boolean` field; semantics unchanged.
- Spark 4.1.1 (audited 2026-05-27): identical to 4.0.1.

## map_contains_key

- Spark 3.4.3 (audited 2026-05-27): identical to 3.5.8.
- Spark 3.5.8 (audited 2026-05-27): baseline. `MapContainsKey(left, right) extends RuntimeReplaceable with InheritAnalysisRules`; the analyzer rewrites to `ArrayContains(MapKeys(left), right)`. Comet routes via `CometMapContainsKey` which emits the equivalent `array_has(map_keys(map), key)`.
- Spark 4.0.1 (audited 2026-05-27): semantics unchanged; minor trait refactors.
- Spark 4.1.1 (audited 2026-05-27): identical to 4.0.1.

## map_entries

- Spark 3.4.3 (audited 2026-05-27): identical to 3.5.8.
- Spark 3.5.8 (audited 2026-05-27): baseline. `MapEntries(child)` returns an array of structs `<key, value>`. Wired to native `map_entries`.
- Spark 4.0.1 (audited 2026-05-27): semantics unchanged.
- Spark 4.1.1 (audited 2026-05-27): identical to 4.0.1.

## map_from_arrays

- Spark 3.4.3 (audited 2026-05-27): identical to 3.5.8.
- Spark 3.5.8 (audited 2026-05-27): baseline. `MapFromArrays(left, right) extends BinaryExpression with NullIntolerant`; Spark uses `ArrayBasedMapBuilder` to detect duplicate keys (subject to `spark.sql.mapKeyDedupPolicy`) and rejects null keys with `RuntimeException("Cannot use null as map key")`. Comet `CometMapFromArrays` wraps the inputs in `CaseWhen(IsNotNull(left) AND IsNotNull(right), map(left, right), null)` so NULL-array inputs return NULL rather than triggering the previously reported native crash ([#3327](https://github.com/apache/datafusion-comet/issues/3327)).
- Spark 4.0.1 (audited 2026-05-27): semantics unchanged; `NullIntolerant` trait replaced by `nullIntolerant: Boolean`.
- Spark 4.1.1 (audited 2026-05-27): identical to 4.0.1.

## map_from_entries

- Spark 3.4.3 (audited 2026-05-27): identical to 3.5.8.
- Spark 3.5.8 (audited 2026-05-27): baseline. `MapFromEntries(child) extends UnaryExpression with NullIntolerant`; expects an array of structs and produces a map. Wired as `CometScalarFunction("map_from_entries")`.
- Spark 4.0.1 (audited 2026-05-27): semantics unchanged; trait refactor.
- Spark 4.1.1 (audited 2026-05-27): identical to 4.0.1.
- Known limitation: input arrays where the struct's key or value type contains `BinaryType` are marked `Incompatible` and fall back unless `spark.comet.expression.MapFromEntries.allowIncompatible=true`.

## map_keys

- Spark 3.4.3 (audited 2026-05-27): identical to 3.5.8.
- Spark 3.5.8 (audited 2026-05-27): baseline. `MapKeys(child)` returns the map's keys as an array. Wired to native `map_keys`.
- Spark 4.0.1 (audited 2026-05-27): semantics unchanged.
- Spark 4.1.1 (audited 2026-05-27): identical to 4.0.1.

## map_values

- Spark 3.4.3 (audited 2026-05-27): identical to 3.5.8.
- Spark 3.5.8 (audited 2026-05-27): baseline. `MapValues(child)` returns the map's values as an array. Wired to native `map_values`.
- Spark 4.0.1 (audited 2026-05-27): semantics unchanged.
- Spark 4.1.1 (audited 2026-05-27): identical to 4.0.1.

## str_to_map

- Spark 3.4.3 (audited 2026-05-27): identical to 3.5.8.
- Spark 3.5.8 (audited 2026-05-27): baseline. `StringToMap(text, pairDelim, keyValueDelim) extends TernaryExpression`; splits `text` on `pairDelim`, then each pair on `keyValueDelim` (default `","` and `":"`). Uses `ArrayBasedMapBuilder` for duplicate-key handling. Wired as `CometScalarFunction("str_to_map")`.
- Spark 4.0.1 (audited 2026-05-27): `inputTypes` widened to `StringTypeNonCSAICollation`; uses `CollationAwareUTF8String.splitSQL` with a `collationId`. Runtime unchanged for `UTF8_BINARY`.
- Spark 4.1.1 (audited 2026-05-27): adds the `legacySplitTruncate` flag (driven by `spark.sql.legacy.truncateForEmptyRegexSplit`) to both `splitSQL` calls. The Comet native impl always behaves as if the flag were false, so `CometStrToMap` reads the config by string key and reports `Incompatible` when it is enabled; the `CodegenDispatchFallback` trait then routes the expression through the JVM codegen dispatcher rather than falling the whole projection back to Spark. Non-UTF8_BINARY collations on the input or the delimiters are handled the same way.

[Spark Expression Support]: ../../user-guide/latest/expressions.md