fix: exclude precision-losing integer-to-float conversions from CastExpr::check_bigger_cast (#23808)

[getChan]

Which issue does this PR close?

• Closes Fix precision loss in CastExpr::check_bigger_cast for integer-to-float conversions #23808.

Rationale for this change

ref. #23807

CastExpr::check_bigger_cast is used to determine whether a cast is a widening (order-preserving) conversion. Currently, it classifies Int32 -> Float32, UInt32 -> Float32, Int64 -> Float64, and UInt64 -> Float64 as widening casts.

However, integer-to-float conversions for 32-bit and 64-bit integers lose precision when values exceed the mantissa bit limit (24 bits for Float32, 53 bits for Float64). For example:
16_777_216_i32 as f32 == 16_777_217_i32 as f32 (both yield 16777216.0f32).

Because distinct integer inputs can collapse to the same float output, these casts are not strictly 1-to-1 (injective) and can break suffix sort key ordering in multi-column ordering analysis (e.g. [CAST(a AS Float32), b]).

What changes are included in this PR?

• Updated CastExpr::check_bigger_cast to exclude precision-losing integer-to-float conversions (Int32/UInt32 -> Float32 and Int64/UInt64 -> Float64).
• Added unit test test_check_bigger_cast_precision_loss to verify precision-losing casts return false while exact conversions (Int16 -> Float32, Int32 -> Float64, etc.) continue to return true.

Are these changes tested?

Yes, new unit test test_check_bigger_cast_precision_loss in cast.rs.

Are there any user-facing changes?

No breaking API changes. Internal optimizer behavior fix.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.63%. Comparing base (9e3c71f) to head (0bc07d5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #23809   +/-   ##
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  Coverage   80.63%   80.63%           
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  Files        1091     1091           
  Lines      370720   370736   +16     
  Branches   370720   370736   +16     
=======================================
+ Hits       298934   298947   +13     
  Misses      53948    53948           
- Partials    17838    17841    +3     

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[nuno-faria]

Thanks @getChan. Since only EquivalenceProperties uses this, it should be ok. However, I think it's better to add some sqllogictests to force this bug. I explored this a bit and here is an example that returns invalid results for the int to float case:

Test data (test.csv):

k,v
1,16777217
2,16777216

-- t1 is defined with the sort order, t2 is not
> create external table t1 (k int, v int) stored as csv with order (v desc, k desc) location 'test.csv';
> create external table t2 (k int, v int) stored as csv location 'test.csv';

-- the result is wrong, since both v_ are equal the k should be switched
> select k, cast(v as float) v_ from t1 order by v_ desc, k desc;
+---+------------+
| k | v_         |
+---+------------+
| 1 | 16777216.0 |
| 2 | 16777216.0 |
+---+------------+

-- using the version without the sort works
> select k, cast(v as float) v_ from t2 order by v_ desc, k desc;
+---+------------+
| k | v_         |
+---+------------+
| 2 | 16777216.0 |
| 1 | 16777216.0 |
+---+------------+

[nuno-faria]

Thanks @getChan.

[alamb]

Thanks @getChan and @nuno-faria