cherry pick pingcap#17116 to release-4.0

Signed-off-by: sre-bot <[email protected]>

executor/set.go

@@ -253,7 +253,7 @@ func (e *SetExecutor) setCharset(cs, co string) error {
 			return errors.Trace(err)
 		}
 	}
-	return errors.Trace(sessionVars.SetSystemVar(variable.CollationConnection, co))
+	return sessionVars.SetSystemVar(variable.CollationConnection, co)
 }
 
 func (e *SetExecutor) getVarValue(v *expression.VarAssignment, sysVar *variable.SysVar) (value types.Datum, err error) {

expression/builtin_info.go

@@ -673,6 +673,7 @@ func (c *collationFunctionClass) getFunction(ctx sessionctx.Context, args []Expr
 	if err != nil {
 		return nil, err
 	}
+	bf.tp.Charset, bf.tp.Collate = ctx.GetSessionVars().GetCharsetInfo()
 	sig := &builtinCollationSig{bf}
 	return sig, nil
 }

expression/integration_test.go

@@ -6372,3 +6372,64 @@ func (s *testIntegrationSuite) TestIssue16697(c *C) {
 		}
 	}
 }
+<<<<<<< HEAD
+=======
+
+func (s *testIntegrationSuite) TestIssue17045(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(a int,b varchar(20),c datetime,d double,e int,f int as(a+b),key(a),key(b),key(c),key(d),key(e),key(f));")
+	tk.MustExec("insert into t(a,b,e) values(null,\"5\",null);")
+	tk.MustExec("insert into t(a,b,e) values(\"5\",null,null);")
+	tk.MustQuery("select /*+ use_index_merge(t)*/ * from t where t.e=5 or t.a=5;").Check(testkit.Rows("5 <nil> <nil> <nil> <nil> <nil>"))
+}
+
+func (s *testIntegrationSuite) TestIssue17098(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t1, t2")
+	tk.MustExec("create table t1(a char) collate utf8mb4_bin;")
+	tk.MustExec("create table t2(a char) collate utf8mb4_bin;;")
+	tk.MustExec("insert into t1 values('a');")
+	tk.MustExec("insert into t2 values('a');")
+	tk.MustQuery("select collation(t1.a) from t1 union select collation(t2.a) from t2;").Check(testkit.Rows("utf8mb4_bin"))
+}
+
+func (s *testIntegrationSuite) TestIssue17115(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustQuery("select collation(user());").Check(testkit.Rows("utf8mb4_bin"))
+	tk.MustQuery("select collation(compress('abc'));").Check(testkit.Rows("binary"))
+}
+
+func (s *testIntegrationSuite) TestIndexedVirtualGeneratedColumnTruncate(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t1")
+	tk.MustExec("create table t(a int, b tinyint as(a+100) unique key)")
+	tk.MustExec("insert ignore into t values(200, default)")
+	tk.MustExec("update t set a=1 where a=200")
+	tk.MustExec("admin check table t")
+	tk.MustExec("delete from t")
+	tk.MustExec("insert ignore into t values(200, default)")
+	tk.MustExec("admin check table t")
+	tk.MustExec("insert ignore into t values(200, default) on duplicate key update a=100")
+	tk.MustExec("admin check table t")
+	tk.MustExec("delete from t")
+	tk.MustExec("admin check table t")
+
+	tk.MustExec("begin")
+	tk.MustExec("insert ignore into t values(200, default)")
+	tk.MustExec("update t set a=1 where a=200")
+	tk.MustExec("admin check table t")
+	tk.MustExec("delete from t")
+	tk.MustExec("insert ignore into t values(200, default)")
+	tk.MustExec("admin check table t")
+	tk.MustExec("insert ignore into t values(200, default) on duplicate key update a=100")
+	tk.MustExec("admin check table t")
+	tk.MustExec("delete from t")
+	tk.MustExec("admin check table t")
+	tk.MustExec("commit")
+	tk.MustExec("admin check table t")
+}
+>>>>>>> ea2e215... *: fix a bug caused by the wrong collation setting which leads to the wrong result of collation function (#17116)

session/session.go

@@ -321,12 +321,7 @@ func (s *session) SetCollation(coID int) error {
 	for _, v := range variable.SetNamesVariables {
 		terror.Log(s.sessionVars.SetSystemVar(v, cs))
 	}
-	err = s.sessionVars.SetSystemVar(variable.CollationConnection, co)
-	if err != nil {
-		// Some clients may use the unsupported collations, such as utf8mb4_0900_ai_ci, We shouldn't return error or use the ERROR level log.
-		logutil.BgLogger().Warn(err.Error())
-	}
-	return nil
+	return s.sessionVars.SetSystemVar(variable.CollationConnection, co)
 }
 
 func (s *session) PreparedPlanCache() *kvcache.SimpleLRUCache {

sessionctx/variable/session.go

@@ -29,6 +29,7 @@ import (
 	"github.com/pingcap/errors"
 	"github.com/pingcap/parser/ast"
 	"github.com/pingcap/parser/auth"
+	"github.com/pingcap/parser/charset"
 	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/parser/terror"
 	pumpcli "github.com/pingcap/tidb-tools/tidb-binlog/pump_client"
@@ -1242,7 +1243,25 @@ func (s *SessionVars) SetSystemVar(name string, val string) error {
 		s.MetricSchemaRangeDuration = tidbOptInt64(val, DefTiDBMetricSchemaRangeDuration)
 	case CollationConnection, CollationDatabase, CollationServer:
 		if _, err := collate.GetCollationByName(val); err != nil {
-			return errors.Trace(err)
+			var ok bool
+			var charsetVal string
+			var err2 error
+			if name == CollationConnection {
+				charsetVal, ok = s.systems[CharacterSetConnection]
+			} else if name == CollationDatabase {
+				charsetVal, ok = s.systems[CharsetDatabase]
+			} else {
+				// CollationServer
+				charsetVal, ok = s.systems[CharacterSetServer]
+			}
+			if !ok {
+				return err
+			}
+			val, err2 = charset.GetDefaultCollation(charsetVal)
+			if err2 != nil {
+				return err2
+			}
+			logutil.BgLogger().Warn(err.Error())
 		}
 	case TiDBSlowLogThreshold:
 		atomic.StoreUint64(&config.GetGlobalConfig().Log.SlowThreshold, uint64(tidbOptInt64(val, logutil.DefaultSlowThreshold)))