style:fix ineffassign and mis-spell (pingcap#9415)

ddl/db_test.go

@@ -2210,6 +2210,7 @@ func (s *testDBSuite) TestCheckConvertToCharacter(c *C) {
 	ctx := s.tk.Se.(sessionctx.Context)
 	is := domain.GetDomain(ctx).InfoSchema()
 	t, err := is.TableByName(model.NewCIStr("test"), model.NewCIStr("t"))
+	c.Assert(err, IsNil)
 	rs, err := s.tk.Exec("alter table t modify column a varchar(10) charset utf8 collate utf8_bin")
 	c.Assert(err, NotNil)
 	rs, err = s.tk.Exec("alter table t modify column a varchar(10) charset utf8mb4 collate utf8mb4_bin")

ddl/ddl_algorithm_test.go

@@ -100,7 +100,7 @@ Loop:
 
 	// Test unsupported.
 	for _, alm := range unsupported {
-		algorithm, err = ddl.ResolveAlterAlgorithm(&tc.alterSpec, alm)
+		_, err = ddl.ResolveAlterAlgorithm(&tc.alterSpec, alm)
 		c.Assert(err, NotNil, Commentf("Tp:%v, alm:%s", tc.alterSpec.Tp, alm))
 		c.Assert(ddl.ErrAlterOperationNotSupported.Equal(err), IsTrue)
 	}

ddl/ddl_api.go

@@ -1438,7 +1438,7 @@ func getCharsetAndCollateInTableOption(startIdx int, options []*ast.TableOption)
 }
 
 // resolveAlterTableSpec resolves alter table algorithm and removes ignore table spec in specs.
-// returns valied specs, and the occured error.
+// returns valied specs, and the occurred error.
 func resolveAlterTableSpec(ctx sessionctx.Context, specs []*ast.AlterTableSpec) ([]*ast.AlterTableSpec, error) {
 	validSpecs := make([]*ast.AlterTableSpec, 0, len(specs))
 	algorithm := ast.AlterAlgorithmDefault
@@ -1469,7 +1469,6 @@ func resolveAlterTableSpec(ctx sessionctx.Context, specs []*ast.AlterTableSpec)
 			// For the compatibility, we return warning instead of error when the algorithm is COPY,
 			// because the COPY ALGORITHM is not supported in TiDB.
 			ctx.GetSessionVars().StmtCtx.AppendError(err)
-			err = nil
 		}
 
 		spec.Algorithm = resolvedAlgorithm