expression: fix reverse function on bit type column (#50146)

expression/builtin_cast.go

@@ -2254,6 +2254,10 @@ func WrapWithCastAsString(ctx sessionctx.Context, expr Expression) Expression {
 		charset, collate := expr.CharsetAndCollation()
 		tp.SetCharset(charset)
 		tp.SetCollate(collate)
+	} else if exprTp.GetType() == mysql.TypeBit {
+		// Implicitly casting BIT to string will make it a binary
+		tp.SetCharset(charset.CharsetBin)
+		tp.SetCollate(charset.CollationBin)
 	} else {
 		charset, collate := ctx.GetSessionVars().GetCharsetInfo()
 		tp.SetCharset(charset)

expression/builtin_string.go

@@ -768,7 +768,7 @@ func (c *reverseFunctionClass) getFunction(ctx sessionctx.Context, args []Expres
 	bf.tp.SetFlen(args[0].GetType().GetFlen())
 	addBinFlag(bf.tp)
 	var sig builtinFunc
-	if types.IsBinaryStr(argTp) {
+	if types.IsBinaryStr(argTp) || types.IsTypeBit(argTp) {
 		sig = &builtinReverseSig{bf}
 		sig.setPbCode(tipb.ScalarFuncSig_Reverse)
 	} else {

expression/collation.go

@@ -177,6 +177,8 @@ func deriveCoercibilityForColumn(c *Column) Coercibility {
 	// For specified type null, it should return CoercibilityIgnorable, which means it got the lowest priority in DeriveCollationFromExprs.
 	if c.RetType.GetType() == mysql.TypeNull {
 		return CoercibilityIgnorable
+	} else if types.IsTypeBit(c.RetType) {
+		return CoercibilityImplicit
 	}
 
 	switch c.RetType.EvalType() {
@@ -374,6 +376,8 @@ func inferCollation(exprs ...Expression) *ExprCollation {
 	dstCharset, dstCollation := exprs[0].GetType().GetCharset(), exprs[0].GetType().GetCollate()
 	if exprs[0].GetType().EvalType() == types.ETJson {
 		dstCharset, dstCollation = charset.CharsetUTF8MB4, charset.CollationUTF8MB4
+	} else if types.IsTypeBit(exprs[0].GetType()) {
+		dstCharset, dstCollation = charset.CharsetBin, charset.CollationBin
 	}
 	unknownCS := false
 
@@ -384,6 +388,8 @@ func inferCollation(exprs ...Expression) *ExprCollation {
 		// see details https://github.com/pingcap/tidb/issues/31320#issuecomment-1010599311
 		if arg.GetType().EvalType() == types.ETJson {
 			argCharset, argCollation = charset.CharsetUTF8MB4, charset.CollationUTF8MB4
+		} else if types.IsTypeBit(arg.GetType()) {
+			argCharset, argCollation = charset.CharsetBin, charset.CollationBin
 		}
 		// If one of the arguments is binary charset, we allow it can be used with other charsets.
 		// If they have the same coercibility, let the binary charset one to be the winner because binary has more precedence.

expression/integration_test/integration_test.go

@@ -7982,3 +7982,46 @@ func TestIssue49526(t *testing.T) {
 	}
 	tk.MustQuery("select null as a union all select 'a' as a;").Sort().Check(testkit.Rows("<nil>", "a"))
 }
+
+func TestIssue49566(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t;")
+	tk.MustExec("create table t (col bit(37) NOT NULL);")
+	tk.MustExec("insert into t (col) values(x'05d3a46d88'), (x'04dba3570c'), (x'0ed284dfee'), (x'12657141bf');")
+	tk.MustQuery("select hex(col), hex(reverse(col)) from t order by reverse(col);").Check(
+		testkit.Rows("4DBA3570C 0C57A3DB04", "5D3A46D88 886DA4D305", "12657141BF BF41716512", "ED284DFEE EEDF84D20E"))
+	tk.MustExec("drop table if exists t;")
+}
+
+func TestIssue50855(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t2;")
+	tk.MustExec("create table t2 (col bit(45) NOT NULL);")
+	tk.MustExec("insert into t2 (col) values(x'09a1441d083c');")
+	tk.MustQuery("select hex(r) from (select reverse(col) as r from t2 group by reverse(col)) as t;").Check(testkit.Rows("3C081D44A109"))
+	tk.MustQuery("select hex(r) from (select distinct reverse(col) as r from t2) as t;").Check(testkit.Rows("3C081D44A109"))
+	tk.MustExec("drop table if exists t2;")
+}
+
+func TestIssue50850(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t3;")
+	tk.MustExec("create table t3 (col1 double not null, col2 bit(8) NOT NULL);")
+	tk.MustExec("insert into t3 (col1, col2) values (2306.9705216860984, x'31'), (6779.239615471537, x'65'), (7601.530447792593, x'd5'), " +
+		"(7058.842877388801, x'a5'), (615.6011553350702, x'34'), (5613.036187642952, x'01'), (7047.649466854864, x'a6'), (8632.659024782468, x'5d'), " +
+		"(9546.629394674586, x'ff'), (2972.7118048537704, x'b1');")
+	tk.MustQuery("select hex(r) as r0 from (select ELT(2, col1, col2) as r from t3 group by ELT(2, col1, col2)) as t order by r0;").Check(
+		testkit.Rows("01", "31", "34", "5D", "65", "A5", "A6", "B1", "D5", "FF"))
+	tk.MustQuery("select hex(r) as r0 from (select distinct ELT(2, col1, col2) as r from t3) as t order by r0;").Check(
+		testkit.Rows("01", "31", "34", "5D", "65", "A5", "A6", "B1", "D5", "FF"))
+	tk.MustExec("drop table if exists t3;")
+}