Introduce ExprVolatility to model constant expressions #19188
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adriangb
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Dec 7, 2025
| /// | ||
| /// # Examples | ||
| /// | ||
| /// ``` |
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| /// ``` | |
| /// ```rust |
| /// | ||
| /// # Examples | ||
| /// | ||
| /// ``` |
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| /// ``` | |
| /// ```rust |
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| matches!( | ||
| expr.volatility(), | ||
| ExprVolatility::Constant | ExprVolatility::Stable | ||
| ) |
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I don't love this, it's a bit confusing. I wonder if the right distinction is Stable with no inputs (e.g. now()?
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| pub is_volatile_node: unsafe extern "C" fn(&Self) -> bool, | ||
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| pub node_volatility: unsafe extern "C" fn(&Self) -> FFI_ExprVolatility, |
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This looks reasonable but is my first time doing FFI work in DataFusion
adriangb
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Dec 7, 2025
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| fn node_volatility(&self) -> ExprVolatility { | ||
| // Although DynamicFilterPhysicalExpr can change its inner expression, | ||
| // from the perspective of optimizer rules it can be treated as immutable | ||
| // so that it can be pushed down, etc. | ||
| ExprVolatility::Immutable | ||
| } |
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This is unfortunate, but I'm not sure how else to model this?
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I got this mostly working but I'm not sure it's the right path forward and don't have the bandwith to work on it so I'll close as an idea and continue discussion in the issue. |
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Closes #19187
This PR was seeded by giving Claude the plan in the linked issue and guidance/supervision.