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# Compatibility Guide

Comet aims to provide consistent results with the version of Apache Spark that is being used.

This guide documents areas where Comet's behavior is known to differ from Spark. Topics are grouped by subsystem:

- **Parquet**: limitations when reading Parquet files (both scan implementations, shared and per-implementation).
- **Floating-point comparison**: NaN and signed-zero handling in comparisons.
- **Regular expressions**: differences between the Rust regexp crate and Java's regex engine.
- **Operators**: operator-level compatibility notes, including window functions and round-robin partitioning.
- **Expressions**: per-expression compatibility notes, including cast.
- **Spark versions**: version-specific known issues and limitations.

```{toctree}
:maxdepth: 1
:hidden:

scans
floating-point
regex
operators
expressions/index
spark-versions
```
