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

close #49566, close #50850, close #50855

pkg/expression/builtin_cast.go

@@ -2272,6 +2272,10 @@ func WrapWithCastAsString(ctx BuildContext, 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)

pkg/expression/builtin_string.go

@@ -767,7 +767,7 @@ func (c *reverseFunctionClass) getFunction(ctx BuildContext, args []Expression)
 	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 {

pkg/expression/collation.go

@@ -176,6 +176,8 @@ 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() {
@@ -373,6 +375,8 @@ 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
 
@@ -383,6 +387,8 @@ 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.

tests/integrationtest/r/expression/builtin.result

@@ -3287,3 +3287,49 @@ RELEASE_LOCK('test_lock3')
 SELECT RELEASE_ALL_LOCKS();
 RELEASE_ALL_LOCKS()
 0
+drop table if exists t;
+create table t (col bit(37) NOT NULL);
+insert into t (col) values(x'05d3a46d88'), (x'04dba3570c'), (x'0ed284dfee'), (x'12657141bf');
+select hex(col), hex(reverse(col)) from t order by reverse(col);
+hex(col)	hex(reverse(col))
+4DBA3570C	0C57A3DB04
+5D3A46D88	886DA4D305
+12657141BF	BF41716512
+ED284DFEE	EEDF84D20E
+drop table if exists t2;
+create table t2 (col bit(45) NOT NULL);
+insert into t2 (col) values (x'09a1441d083c');
+select hex(r) from (select REVERSE(col) as r from t2 group by REVERSE(col)) as t;
+hex(r)
+3C081D44A109
+select hex(r) from (select distinct REVERSE(col) as r from t2) as t;
+hex(r)
+3C081D44A109
+drop table if exists t3;
+create table t3 (col1 double NOT NULL, col2 bit(8) NOT NULL);
+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');
+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;
+r0
+01
+31
+34
+5D
+65
+A5
+A6
+B1
+D5
+FF
+select hex(r) as r0 from (select distinct ELT(2, col1, col2) as r from t3) as t order by r0;
+r0
+01
+31
+34
+5D
+65
+A5
+A6
+B1
+D5
+FF
+drop table t, t2, t3;

tests/integrationtest/t/expression/builtin.test

@@ -1560,3 +1560,21 @@ SELECT RELEASE_LOCK('test_lock1');
 SELECT RELEASE_LOCK('test_lock3');
 SELECT RELEASE_ALL_LOCKS();
 
+# Issue #49566
+drop table if exists t;
+create table t (col bit(37) NOT NULL);
+insert into t (col) values(x'05d3a46d88'), (x'04dba3570c'), (x'0ed284dfee'), (x'12657141bf');
+select hex(col), hex(reverse(col)) from t order by reverse(col);
+# Issue #50855
+drop table if exists t2;
+create table t2 (col bit(45) NOT NULL);
+insert into t2 (col) values (x'09a1441d083c');
+select hex(r) from (select REVERSE(col) as r from t2 group by REVERSE(col)) as t;
+select hex(r) from (select distinct REVERSE(col) as r from t2) as t;
+# Issue #50850
+drop table if exists t3;
+create table t3 (col1 double NOT NULL, col2 bit(8) NOT NULL);
+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');
+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;
+select hex(r) as r0 from (select distinct ELT(2, col1, col2) as r from t3) as t order by r0;
+drop table t, t2, t3;