alamb commented on code in PR #22114:
URL: https://github.com/apache/datafusion/pull/22114#discussion_r4269770164
##########
datafusion/functions/src/datetime/date_trunc.rs:
##########
@@ -587,8 +687,313 @@ where
1 + 3 * ((date.month() - 1) / 3)
}
+/// Extract an `i64` timestamp value from a literal that matches the column's
+/// `(unit, tz)`. Returns `None` if the literal is null or not a matching
Review Comment:
I think this only supports `None` timestamps, right?
##########
datafusion/functions/src/datetime/date_trunc.rs:
##########
@@ -436,16 +457,93 @@ impl ScalarUDFImpl for DateTruncFunc {
&self.aliases
}
+ /// Compute the preimage for `date_trunc(granularity, col) = literal`.
+ ///
+ /// `date_trunc` floors a timestamp to the start of the given period, so
+ /// for any aligned literal `L` the preimage is the half-open interval
+ /// `[L, L + 1 granularity)`.
+ fn preimage(
+ &self,
+ args: &[Expr],
+ lit_expr: &Expr,
+ info: &SimplifyContext,
+ ) -> Result<PreimageResult> {
+ let [precision, col_expr] = take_function_args(self.name(), args)?;
+
+ // Granularity literal (e.g. "month").
+ let Some(granularity) = precision
+ .as_literal()
+ .and_then(|sv| sv.try_as_str().flatten())
+ .and_then(|s| DateTruncGranularity::from_str(s).ok())
+ else {
+ return Ok(PreimageResult::None);
+ };
+
+ // If the column is a Date32/Date64 wrapped in the signature's implicit
+ // cast to Timestamp(ns), emit bounds in the Date type against the raw
+ // column. `unwrap_cast_in_comparison` doesn't currently support Date
Review Comment:
What does this mean that `unwrap_cast_in_comparison` doesn't support Date
targets?
That sounds like a gap we should fix (as a separate PR)
- https://github.com/apache/datafusion/issues/26289
##########
datafusion/functions/src/datetime/date_trunc.rs:
##########
@@ -587,8 +687,313 @@ where
1 + 3 * ((date.month() - 1) / 3)
}
+/// Extract an `i64` timestamp value from a literal that matches the column's
+/// `(unit, tz)`. Returns `None` if the literal is null or not a matching
+/// `Timestamp*` variant — the simplifier is responsible for coercing the
+/// literal first, so a mismatch here means the rewrite is not applicable.
+/// Peel the signature-inserted `Cast(date_col, Timestamp(ns))` wrapper and
+/// emit Date-type preimage bounds against the raw column. Returns `None` if
+/// the column isn't a Date wrapped in the expected cast, or if the literal
+/// isn't a midnight-UTC value aligned to the granularity boundary.
+fn date_column_preimage(
+ col_expr: &Expr,
+ lit_expr: &Expr,
+ granularity: DateTruncGranularity,
+ info: &SimplifyContext,
+) -> Option<PreimageResult> {
+ // The signature wraps Date columns as exactly Cast(_,
Timestamp(Nanosecond, None)).
Review Comment:
Update -- filed an issue
- https://github.com/apache/datafusion/issues/26289
##########
datafusion/functions/src/datetime/date_trunc.rs:
##########
@@ -587,8 +687,313 @@ where
1 + 3 * ((date.month() - 1) / 3)
}
+/// Extract an `i64` timestamp value from a literal that matches the column's
+/// `(unit, tz)`. Returns `None` if the literal is null or not a matching
+/// `Timestamp*` variant — the simplifier is responsible for coercing the
+/// literal first, so a mismatch here means the rewrite is not applicable.
+/// Peel the signature-inserted `Cast(date_col, Timestamp(ns))` wrapper and
+/// emit Date-type preimage bounds against the raw column. Returns `None` if
+/// the column isn't a Date wrapped in the expected cast, or if the literal
+/// isn't a midnight-UTC value aligned to the granularity boundary.
+fn date_column_preimage(
+ col_expr: &Expr,
+ lit_expr: &Expr,
+ granularity: DateTruncGranularity,
+ info: &SimplifyContext,
+) -> Option<PreimageResult> {
+ // The signature wraps Date columns as exactly Cast(_,
Timestamp(Nanosecond, None)).
Review Comment:
this is weird to me -- it seems like this should have been simplified to me
(like constants evaluated so the cast was already evaluated)
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