review: better doc

Author: 2010YOUY01

datafusion/functions/src/string/common.rs

@@ -522,7 +522,7 @@ fn case_conversion_utf8view_ascii_inner<F: Fn(&u8) -> u8>(
                 let to_reserve = len.max(block_size as usize);
                 #[expect(
                     clippy::disallowed_methods,
-                    reason = "StringView block_size bounds growth, so reserve cannot overflow capacity"
+                    reason = "StringView's block size bounds growth, so reserve cannot overflow capacity arithmetically. This hot loop intentionally avoids the extra `try_reserve` checks. It remains subject to allocator failure/OOM, which must be managed externally."
                 )]
                 in_progress.reserve(to_reserve);
             }

datafusion/functions/src/strings.rs

@@ -705,7 +705,7 @@ impl StringViewArrayBuilder {
             let to_reserve = (length as usize).max(self.next_block_size() as usize);
             #[expect(
                 clippy::disallowed_methods,
-                reason = "StringView block_size bounds growth, so reserve cannot overflow capacity"
+                reason = "StringView's block size bounds growth, so reserve cannot overflow capacity arithmetically. This hot loop intentionally avoids the extra `try_reserve` checks. It remains subject to allocator failure/OOM, which must be managed externally."
             )]
             self.in_progress.reserve(to_reserve);
         }
@@ -736,7 +736,7 @@ impl StringViewArrayBuilder {
             let to_reserve = (length as usize).max(self.next_block_size() as usize);
             #[expect(
                 clippy::disallowed_methods,
-                reason = "StringView block_size bounds growth, so reserve cannot overflow capacity"
+                reason = "StringView's block size bounds growth, so reserve cannot overflow capacity arithmetically. This hot loop intentionally avoids the extra `try_reserve` checks. It remains subject to allocator failure/OOM, which must be managed externally."
             )]
             self.in_progress.reserve(to_reserve);
         }