jayzhan211 commented on code in PR #22906:
URL: https://github.com/apache/datafusion/pull/22906#discussion_r4319612498
##########
datafusion/expr-common/src/casts.rs:
##########
@@ -76,6 +112,501 @@ pub fn try_cast_literal_to_type(
.or_else(|| try_cast_binary(lit_value, target_type))
}
+/// Computes a source-domain preimage for `CAST(source AS target_type) OP
literal`.
+///
+/// This is the shared semantic core for logical and physical cast-predicate
+/// rewrites. It returns an exact same-operator source bound or literal as
+/// [`CastPredicatePreimage::Exact`] where moving the cast preserves comparison
+/// semantics subject to the documented family-level overflow exceptions, and a
+/// [`CastPredicatePreimage::Range`] for many-to-one casts with known preimages
+/// such as timestamp precision narrowing.
+pub fn cast_predicate_preimage(
Review Comment:
The decimal change looks good, thanks for adding the Bloom-filter test. Fine
to do this in a follow-up: every timestamp unit pair can use one interval.
Narrowing takes the truncation bucket and widening takes `[ceil(v/r),
floor(v/r) + 1)`. A singleton becomes `Exact`, an empty interval with
`=`/`!=`/`IN` returns `None`, and anything else becomes `Range`. That replaces
`maybe_range_preimage`, `timestamp_widening_ordered_preimage` and the
round-trip check, and in my local try it removed about 100 non-test lines. The
dispatcher needs to strip one `Dictionary` level first so dictionary-encoded
timestamps keep their rewrites.
```rs
let (lower, upper) = if source_scale > target_scale {
let Some(bucket) = trunc_toward_zero_bucket(value, source_scale /
target_scale) else {
return Ok(None);
};
bucket
} else {
let ratio = target_scale / source_scale;
let floor = value.div_euclid(ratio);
let ceil = floor + i128::from(value.rem_euclid(ratio) != 0);
(ceil, floor + 1)
};
```
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