copr: fix neg sign when decimal divide to zero (#11302) (#11335)

ref #11302, close pingcap/tidb#29586

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

Co-authored-by: Zhuomin Liu <lzmhhh123@gmail.com>
Co-authored-by: Ti Chi Robot <ti-community-prow-bot@tidb.io>

components/tidb_query_datatype/src/codec/mysql/decimal.rs

@@ -765,6 +765,9 @@ fn do_div_mod_impl(
  let dest = &mut res.word_buf[idx_to..idx_to + src.len()];
  dest.copy_from_slice(src);
  }
+ if res.is_zero() {
+ res.negative = false
+ }
  Some(res)
 }
 
@@ -3495,9 +3498,23 @@ mod tests {
  0,
  "-0.000000000000000000000000000000000000000000004078816115216077",
  "770994069125765500000000000000000000000000000",
- Some("-0.000000000000000000000000000000000000000000000000000000000000000"),
+ Some("0.000000000000000000000000000000000000000000000000000000000000000"),
  Some("-0.000000000000000000000000000000000000000000004078816115216077"),
  ),
+ (
+ DEFAULT_DIV_FRAC_INCR,
+ "-125",
+ "489466941506",
+ Some("0.000000000"),
+ Some("-125"),
+ ),
+ (
+ DEFAULT_DIV_FRAC_INCR,
+ "-56",
+ "489466941506",
+ Some("0.000000000"),
+ Some("-56"),
+ ),
  ];
 
  for (frac_incr, lhs_str, rhs_str, div_exp, rem_exp) in cases {