[PR] fix(arrow/array): use scale-aware ValueStr in decimal array String() [arrow-go]

["zeroshade (via GitHub)" <gi...@apache.org>]

zeroshade opened a new pull request, #849:
URL: https://github.com/apache/arrow-go/pull/849

   ### Rationale for this change
   
   Decimal arrays stringify the raw `decimal.Num` struct instead of the scaled logical value. `fmt.Println` on a decimal array — or on a `Record`/`RecordBatch` containing one — prints e.g. `{1999 0}` instead of `19.99`, even though `ValueStr` already formats the value correctly using the type's scale. This is inconsistent with `ValueStr`/JSON output and with other Arrow implementations (e.g. PyArrow prints `19.99`).
   
   ### What changes are included in this PR?
   
   - `baseDecimal[T].String()` now formats each non-null value via `ValueStr` (which applies the type's scale through `GetOneForMarshal`) instead of `fmt.Sprintf("%v", Value(i))`. Because `baseDecimal` is generic, this corrects `Decimal32/64/128/256` at once, and `RecordBatch` printing inherits the fix through the column `String()` path (`record.go`).
   - Updated two existing slice-test assertions in `decimal128_test.go` / `decimal256_test.go` that pinned the old raw-struct output (they were already inconsistent with the adjacent `ValueStr` expectations on the next lines).
   - Added `TestDecimal128StringScaled`, reproducing the issue (`decimal128(5, 2)` = `19.99`) and asserting both the array `String()` and the `RecordBatch` output.
   
   ### Are these changes tested?
   
   Yes. `go test ./arrow/array/` passes, including the new regression test and the updated slice tests. `go build ./...` and `go vet`/golangci-lint (via pre-commit) pass.
   
   ### Are there any user-facing changes?
   
   Yes — the textual output of `String()` on decimal arrays, and of any `Record`/`RecordBatch` containing decimal columns, now shows scaled decimal values (e.g. `19.99`) instead of the internal struct (e.g. `{1999 0}`). This only affects human-readable stringification; binary/IPC/JSON representations are unchanged.
   
   Closes #848
   


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Re: [PR] fix(arrow/array): use scale-aware ValueStr in decimal array String() [arrow-go]

["zeroshade (via GitHub)" <gi...@apache.org>]

zeroshade merged PR #849:
URL: https://github.com/apache/arrow-go/pull/849


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