cherry pick #24297 to release-5.0

Signed-off-by: ti-srebot <[email protected]>
pingcap · Apr 26, 2021 · 675f854 · 675f854
1 parent 1145e34
commit 675f854
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Showing 2 changed files with 12 additions and 1 deletion.
diff --git a/expression/builtin_cast.go b/expression/builtin_cast.go
@@ -1906,7 +1906,11 @@ func WrapWithCastAsString(ctx sessionctx.Context, expr Expression) Expression {
 		argLen = -1
 	}
 	tp := types.NewFieldType(mysql.TypeVarString)
-	tp.Charset, tp.Collate = expr.CharsetAndCollation(ctx)
+	if expr.Coercibility() == CoercibilityExplicit {
+		tp.Charset, tp.Collate = expr.CharsetAndCollation(ctx)
+	} else {
+		tp.Charset, tp.Collate = ctx.GetSessionVars().GetCharsetInfo()
+	}
 	tp.Flen, tp.Decimal = argLen, types.UnspecifiedLength
 	return BuildCastFunction(ctx, expr, tp)
 }

diff --git a/expression/integration_test.go b/expression/integration_test.go
@@ -7744,6 +7744,7 @@ func (s *testIntegrationSerialSuite) TestIssue19116(c *C) {
 	defer collate.SetNewCollationEnabledForTest(false)
 
 	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
 	tk.MustExec("set names utf8mb4 collate utf8mb4_general_ci;")
 	tk.MustQuery("select collation(concat(1 collate `binary`));").Check(testkit.Rows("binary"))
 	tk.MustQuery("select coercibility(concat(1 collate `binary`));").Check(testkit.Rows("0"))
@@ -7754,6 +7755,12 @@ func (s *testIntegrationSerialSuite) TestIssue19116(c *C) {
 	tk.MustQuery("select collation(1);").Check(testkit.Rows("binary"))
 	tk.MustQuery("select coercibility(1);").Check(testkit.Rows("5"))
 	tk.MustQuery("select coercibility(1=1);").Check(testkit.Rows("5"))
+
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(a datetime)")
+	tk.MustExec("insert into t values ('2020-02-02')")
+	tk.MustQuery("select collation(concat(unix_timestamp(a))) from t;").Check(testkit.Rows("utf8mb4_general_ci"))
+	tk.MustQuery("select coercibility(concat(unix_timestamp(a))) from t;").Check(testkit.Rows("4"))
 }
 
 // issues 14448, 19383, 17734