util: fix bad number error with DISTINCT when dividing long decimals (#…

…21783)
pingcap · Dec 18, 2020 · e9b11b7 · e9b11b7
1 parent 503819b
commit e9b11b7
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Showing 2 changed files with 9 additions and 0 deletions.
diff --git a/executor/executor_test.go b/executor/executor_test.go
@@ -7267,3 +7267,8 @@ func (s *testSuite) Test12201(c *C) {
 	tk.MustQuery("select * from e where case e when 1 then e end").Check(testkit.Rows("a"))
 	tk.MustQuery("select * from e where case 1 when e then e end").Check(testkit.Rows("a"))
 }
+
+func (s *testSuite) TestIssue15563(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustQuery("select distinct 0.7544678906163867 /  0.68234634;").Check(testkit.Rows("1.10569639842486251190"))
+}
diff --git a/util/codec/decimal.go b/util/codec/decimal.go
@@ -16,6 +16,7 @@ package codec
 import (
 	"github.com/pingcap/errors"
 	"github.com/pingcap/failpoint"
+	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb/types"
 )
 
@@ -24,6 +25,9 @@ func EncodeDecimal(b []byte, dec *types.MyDecimal, precision, frac int) ([]byte,
 	if precision == 0 {
 		precision, frac = dec.PrecisionAndFrac()
 	}
+	if frac > mysql.MaxDecimalScale {
+		frac = mysql.MaxDecimalScale
+	}
 	b = append(b, byte(precision), byte(frac))
 	b, err := dec.WriteBin(precision, frac, b)
 	return b, errors.Trace(err)