Properly cast ENUMs to TEXT for CASE and CONVERT statements (#2791)

Author: jycor

enginetest/queries/script_queries.go

@@ -7641,14 +7641,14 @@ where
 	},
 	{
 		// https://github.com/dolthub/dolt/issues/8598
-		Name: "enum cast to int and string",
+		Name:    "enum cast to int and string",
+		Dialect: "mysql",
 		SetUpScript: []string{
 			"create table t (i int primary key, e enum('abc', 'def', 'ghi'));",
 			"insert into t values (1, 'abc'), (2, 'def'), (3, 'ghi');",
 		},
 		Assertions: []ScriptTestAssertion{
 			{
-				Skip:  true,
 				Query: "select i, cast(e as signed) from t;",
 				Expected: []sql.Row{
 					{1, 1},
@@ -7657,14 +7657,46 @@ where
 				},
 			},
 			{
-				Skip:  true,
 				Query: "select i, cast(e as char) from t;",
 				Expected: []sql.Row{
 					{1, "abc"},
 					{2, "def"},
 					{3, "ghi"},
 				},
 			},
+			{
+				Query: "select i, cast(e as binary) from t;",
+				Expected: []sql.Row{
+					{1, []uint8("abc")},
+					{2, []uint8("def")},
+					{3, []uint8("ghi")},
+				},
+			},
+			{
+				Query: "select case when e = 'abc' then 'abc' when e = 'def' then 123 else e end from t",
+				Expected: []sql.Row{
+					{"abc"},
+					{"123"},
+					{"ghi"},
+				},
+			},
+		},
+	},
+	{
+		Name:    "enum errors",
+		Dialect: "mysql",
+		SetUpScript: []string{
+			"create table t (i int primary key, e enum('abc', 'def', 'ghi'));",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Query:          "insert into t values (1, 500)",
+				ExpectedErrStr: "value 500 is not valid for this Enum",
+			},
+			{
+				Query:          "insert into t values (1, -1)",
+				ExpectedErrStr: "value -1 is not valid for this Enum",
+			},
 		},
 	},
 }

sql/expression/enum.go

@@ -0,0 +1,93 @@
+// Copyright 2024 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package expression
+
+import (
+	"github.com/dolthub/go-mysql-server/sql"
+	"github.com/dolthub/go-mysql-server/sql/types"
+)
+
+// EnumToString is an expression that converts an enum value to a string.
+type EnumToString struct {
+	Enum sql.Expression
+}
+
+var _ sql.Expression = (*EnumToString)(nil)
+var _ sql.CollationCoercible = (*EnumToString)(nil)
+
+func NewEnumToString(enum sql.Expression) *EnumToString {
+	return &EnumToString{Enum: enum}
+}
+
+// Type implements the sql.Expression interface.
+func (e *EnumToString) Type() sql.Type {
+	return types.Text
+}
+
+// CollationCoercibility implements the interface sql.CollationCoercible.
+func (e *EnumToString) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
+	return e.Type().CollationCoercibility(ctx)
+}
+
+// IsNullable implements the sql.Expression interface.
+func (e *EnumToString) IsNullable() bool {
+	return e.Enum.IsNullable()
+}
+
+// Resolved implements the sql.Expression interface.
+func (e *EnumToString) Resolved() bool {
+	return e.Enum.Resolved()
+}
+
+// Children implements the sql.Expression interface.
+func (e *EnumToString) Children() []sql.Expression {
+	return []sql.Expression{e.Enum}
+}
+
+// Eval implements the sql.Expression interface.
+func (e *EnumToString) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
+	span, ctx := ctx.Span("expression.EnumToString")
+	defer span.End()
+
+	val, err := e.Enum.Eval(ctx, row)
+	if err != nil {
+		return nil, err
+	}
+	if val == nil {
+		return nil, nil
+	}
+
+	enumType := e.Enum.Type().(types.EnumType)
+	str, _ := enumType.At(int(val.(uint16)))
+	return str, nil
+}
+
+// WithChildren implements the Expression interface.
+func (e *EnumToString) WithChildren(children ...sql.Expression) (sql.Expression, error) {
+	if len(children) != 1 {
+		return nil, sql.ErrInvalidChildrenNumber.New(e, len(children), 1)
+	}
+
+	return NewEnumToString(children[0]), nil
+}
+
+// String implements the sql.Expression interface.
+func (e *EnumToString) String() string {
+	return e.Enum.String()
+}
+
+// DebugString implements the sql.Expression interface.
+func (e *EnumToString) DebugString() string {
+	return sql.DebugString(e.Enum)
+}

sql/planbuilder/factory.go

@@ -17,6 +17,8 @@ package planbuilder
 import (
 	"strings"
 
+	"github.com/dolthub/go-mysql-server/sql/types"
+
 	"github.com/dolthub/go-mysql-server/sql"
 	"github.com/dolthub/go-mysql-server/sql/expression"
 	"github.com/dolthub/go-mysql-server/sql/plan"
@@ -132,6 +134,13 @@ func (f *factory) buildConvert(expr sql.Expression, castToType string, typeLengt
 			return expr, nil
 		}
 	}
+	if types.IsText(n.Type()) && types.IsEnum(expr.Type()) {
+		newNode, err := n.WithChildren(expression.NewEnumToString(expr))
+		if err != nil {
+			return nil, err
+		}
+		return newNode, nil
+	}
 	return n, nil
 }
 

sql/planbuilder/scalar.go

@@ -794,7 +794,20 @@ func (b *Builder) caseExprToExpression(inScope *scope, e *ast.CaseExpr) (sql.Exp
 		elseExpr = b.buildScalar(inScope, e.Else)
 	}
 
-	return expression.NewCase(expr, branches, elseExpr), nil
+	newCase := expression.NewCase(expr, branches, elseExpr)
+	if types.IsText(newCase.Type()) {
+		for _, branch := range branches {
+			if types.IsEnum(branch.Value.Type()) {
+				branch.Value = expression.NewEnumToString(branch.Value)
+			}
+		}
+		if elseExpr != nil && types.IsEnum(elseExpr.Type()) {
+			elseExpr = expression.NewEnumToString(elseExpr)
+		}
+		newCase = expression.NewCase(expr, branches, elseExpr)
+	}
+
+	return newCase, nil
 }
 
 func (b *Builder) intervalExprToExpression(inScope *scope, e *ast.IntervalExpr) *expression.Interval {

sql/types/conversion.go

@@ -517,11 +517,11 @@ func TypesEqual(a, b sql.Type) bool {
 	case EnumType:
 		aEnumType := at
 		bEnumType := b.(EnumType)
-		if len(aEnumType.indexToVal) != len(bEnumType.indexToVal) {
+		if len(aEnumType.idxToVal) != len(bEnumType.idxToVal) {
 			return false
 		}
-		for i := 0; i < len(aEnumType.indexToVal); i++ {
-			if aEnumType.indexToVal[i] != bEnumType.indexToVal[i] {
+		for i := 0; i < len(aEnumType.idxToVal); i++ {
+			if aEnumType.idxToVal[i] != bEnumType.idxToVal[i] {
 				return false
 			}
 		}

sql/types/enum.go

@@ -48,9 +48,9 @@ var (
 
 type EnumType struct {
 	collation             sql.CollationID
-	hashedValToIndex      map[uint64]int
+	hashedValToIdx        map[uint64]int
 	valToIdx              map[string]int
-	indexToVal            []string
+	idxToVal              []string
 	maxResponseByteLength uint32
 }
 
@@ -98,8 +98,8 @@ func CreateEnumType(values []string, collation sql.CollationID) (sql.EnumType, e
 	}
 	return EnumType{
 		collation:             collation,
-		hashedValToIndex:      hashedValToIndex,
-		indexToVal:            values,
+		hashedValToIdx:        hashedValToIndex,
+		idxToVal:              values,
 		valToIdx:              valToIdx,
 		maxResponseByteLength: maxResponseByteLength,
 	}, nil
@@ -217,9 +217,9 @@ func (t EnumType) MustConvert(v interface{}) interface{} {
 
 // Equals implements the Type interface.
 func (t EnumType) Equals(otherType sql.Type) bool {
-	if ot, ok := otherType.(EnumType); ok && t.collation.Equals(ot.collation) && len(t.indexToVal) == len(ot.indexToVal) {
-		for i, val := range t.indexToVal {
-			if ot.indexToVal[i] != val {
+	if ot, ok := otherType.(EnumType); ok && t.collation.Equals(ot.collation) && len(t.idxToVal) == len(ot.idxToVal) {
+		for i, val := range t.idxToVal {
+			if ot.idxToVal[i] != val {
 				return false
 			}
 		}
@@ -289,16 +289,19 @@ func (t EnumType) Zero() interface{} {
 }
 
 // At implements EnumType interface.
-func (t EnumType) At(index int) (string, bool) {
-	// The elements listed in the column specification are assigned index numbers, beginning with 1.
-	index -= 1
-	if index <= -1 {
-		// for index zero, the value is empty. It's used for insert ignore.
+func (t EnumType) At(idx int) (string, bool) {
+	// for index zero, the value is empty. It's used for insert ignore.
+	if idx < 0 {
+		return "", false
+	}
+	if idx == 0 {
 		return "", true
-	} else if index >= len(t.indexToVal) {
+	}
+	if idx > len(t.idxToVal) {
 		return "", false
 	}
-	return t.indexToVal[index], true
+	// The elements listed in the column specification are assigned index numbers, beginning with 1.
+	return t.idxToVal[idx-1], true
 }
 
 // CharacterSet implements EnumType interface.
@@ -318,7 +321,7 @@ func (t EnumType) IndexOf(v string) int {
 	}
 	hashedVal, err := t.collation.HashToUint(v)
 	if err == nil {
-		if index, ok := t.hashedValToIndex[hashedVal]; ok {
+		if index, ok := t.hashedValToIdx[hashedVal]; ok {
 			return index
 		}
 	}
@@ -334,24 +337,24 @@ func (t EnumType) IndexOf(v string) int {
 
 // NumberOfElements implements EnumType interface.
 func (t EnumType) NumberOfElements() uint16 {
-	return uint16(len(t.indexToVal))
+	return uint16(len(t.idxToVal))
 }
 
 // Values implements EnumType interface.
 func (t EnumType) Values() []string {
-	vals := make([]string, len(t.indexToVal))
-	copy(vals, t.indexToVal)
+	vals := make([]string, len(t.idxToVal))
+	copy(vals, t.idxToVal)
 	return vals
 }
 
 // WithNewCollation implements sql.TypeWithCollation interface.
 func (t EnumType) WithNewCollation(collation sql.CollationID) (sql.Type, error) {
-	return CreateEnumType(t.indexToVal, collation)
+	return CreateEnumType(t.idxToVal, collation)
 }
 
 // StringWithTableCollation implements sql.TypeWithCollation interface.
 func (t EnumType) StringWithTableCollation(tableCollation sql.CollationID) string {
-	s := fmt.Sprintf("enum('%v')", strings.Join(t.indexToVal, `','`))
+	s := fmt.Sprintf("enum('%v')", strings.Join(t.idxToVal, `','`))
 	if t.CharacterSet() != tableCollation.CharacterSet() {
 		s += " CHARACTER SET " + t.CharacterSet().String()
 	}