diff --git a/enginetest/queries/script_queries.go b/enginetest/queries/script_queries.go
index b6657abc91..102c39b801 100644
--- a/enginetest/queries/script_queries.go
+++ b/enginetest/queries/script_queries.go
@@ -5897,6 +5897,257 @@ where
 			},
 		},
 	},
+	{
+		Name: "varchar primary key",
+		SetUpScript: []string{
+			"create table vt (v varchar(3) primary key);",
+			"insert into vt values ('abc'), ('def'), ('ghi');",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Query: "select * from vt where v = 'def';",
+				Expected: []sql.Row{
+					{"def"},
+				},
+			},
+			{
+				Query: "select * from vt where v < 'def';",
+				Expected: []sql.Row{
+					{"abc"},
+				},
+			},
+			{
+				Query: "select * from vt where v > 'def';",
+				Expected: []sql.Row{
+					{"ghi"},
+				},
+			},
+			{
+				Query: "select * from vt where v <= 'def';",
+				Expected: []sql.Row{
+					{"abc"},
+					{"def"},
+				},
+			},
+			{
+				Query: "select * from vt where v >= 'def';",
+				Expected: []sql.Row{
+					{"def"},
+					{"ghi"},
+				},
+			},
+
+			{
+				Query:    "select * from vt where v = 'defdef';",
+				Expected: []sql.Row{},
+			},
+			{
+				Query: "select * from vt where v < 'defdef';",
+				Expected: []sql.Row{
+					{"abc"},
+					{"def"},
+				},
+			},
+			{
+				Query: "select * from vt where v > 'defdef';",
+				Expected: []sql.Row{
+					{"ghi"},
+				},
+			},
+			{
+				Query: "select * from vt where v <= 'defdef';",
+				Expected: []sql.Row{
+					{"abc"},
+					{"def"},
+				},
+			},
+			{
+				Query: "select * from vt where v >= 'defdef';",
+				Expected: []sql.Row{
+					{"ghi"},
+				},
+			},
+
+			// MySQL behavior around null bytes is strange
+			{
+				Skip:  true,
+				Query: `select * from vt where v = 'def\0\0';`,
+				Expected: []sql.Row{
+					{"def"},
+				},
+			},
+			{
+				Skip:  true,
+				Query: `select * from vt where v < 'def\0\0';`,
+				Expected: []sql.Row{
+					{"abc"},
+				},
+			},
+			{
+				Query: `select * from vt where v > 'def\0\0';`,
+				Expected: []sql.Row{
+					{"ghi"},
+				},
+			},
+			{
+				Query: `select * from vt where v <= 'def\0\0';`,
+				Expected: []sql.Row{
+					{"abc"},
+					{"def"},
+				},
+			},
+			{
+				Skip:  true,
+				Query: `select * from vt where v >= 'def\0\0';`,
+				Expected: []sql.Row{
+					{"def"},
+					{"ghi"},
+				},
+			},
+
+			{
+				Query: "select * from vt where v = cast('def' as char(6));",
+				Expected: []sql.Row{
+					{"def"},
+				},
+			},
+			{
+				Query: "select * from vt where v < cast('def' as char(6));",
+				Expected: []sql.Row{
+					{"abc"},
+				},
+			},
+			{
+				Query: "select * from vt where v > cast('def' as char(6));",
+				Expected: []sql.Row{
+					{"ghi"},
+				},
+			},
+			{
+				Query: "select * from vt where v <= cast('def' as char(6));",
+				Expected: []sql.Row{
+					{"abc"},
+					{"def"},
+				},
+			},
+			{
+				Query: "select * from vt where v >= cast('def' as char(6));",
+				Expected: []sql.Row{
+					{"def"},
+					{"ghi"},
+				},
+			},
+		},
+	},
+	{
+		Name: "varbinary primary key",
+		SetUpScript: []string{
+			"create table vt (v varbinary(3) primary key);",
+			"insert into vt values ('abc'), ('def'), ('ghi');",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Query: "select cast(v as char(3)) from vt where v = 'def';",
+				Expected: []sql.Row{
+					{"def"},
+				},
+			},
+			{
+				Query: "select cast(v as char(3)) from vt where v < 'def';",
+				Expected: []sql.Row{
+					{"abc"},
+				},
+			},
+			{
+				Query: "select cast(v as char(3)) from vt where v > 'def';",
+				Expected: []sql.Row{
+					{"ghi"},
+				},
+			},
+			{
+				Query: "select cast(v as char(3)) from vt where v <= 'def';",
+				Expected: []sql.Row{
+					{"abc"},
+					{"def"},
+				},
+			},
+			{
+				Query: "select cast(v as char(3)) from vt where v >= 'def';",
+				Expected: []sql.Row{
+					{"def"},
+					{"ghi"},
+				},
+			},
+
+			{
+				Query:    "select cast(v as char(3)) from vt where v = 'defdef';",
+				Expected: []sql.Row{},
+			},
+			{
+				Query: "select cast(v as char(3)) from vt where v < 'defdef';",
+				Expected: []sql.Row{
+					{"abc"},
+					{"def"},
+				},
+			},
+			{
+				Query: "select cast(v as char(3)) from vt where v > 'defdef';",
+				Expected: []sql.Row{
+					{"ghi"},
+				},
+			},
+			{
+				Query: "select cast(v as char(3)) from vt where v <= 'defdef';",
+				Expected: []sql.Row{
+					{"abc"},
+					{"def"},
+				},
+			},
+			{
+				Query: "select cast(v as char(3)) from vt where v >= 'defdef';",
+				Expected: []sql.Row{
+					{"ghi"},
+				},
+			},
+
+			// MySQL behavior around null bytes is strange
+			{
+				Skip:  true,
+				Query: `select cast(v as char(3)) from vt where v = 'def\0\0';`,
+				Expected: []sql.Row{
+					{"def"},
+				},
+			},
+			{
+				Skip:  true,
+				Query: `select cast(v as char(3)) from vt where v < 'def\0\0';`,
+				Expected: []sql.Row{
+					{"abc"},
+				},
+			},
+			{
+				Query: `select cast(v as char(3)) from vt where v > 'def\0\0';`,
+				Expected: []sql.Row{
+					{"ghi"},
+				},
+			},
+			{
+				Query: `select cast(v as char(3)) from vt where v <= 'def\0\0';`,
+				Expected: []sql.Row{
+					{"abc"},
+					{"def"},
+				},
+			},
+			{
+				Skip:  true,
+				Query: `select cast(v as char(3)) from vt where v >= 'def\0\0';`,
+				Expected: []sql.Row{
+					{"def"},
+					{"ghi"},
+				},
+			},
+		},
+	},
 }
 
 var SpatialScriptTests = []ScriptTest{
diff --git a/sql/index_builder.go b/sql/index_builder.go
index 3254c08862..9e675fe614 100644
--- a/sql/index_builder.go
+++ b/sql/index_builder.go
@@ -44,8 +44,12 @@ func NewIndexBuilder(idx Index) *IndexBuilder {
 	colExprTypes := make(map[string]Type)
 	ranges := make(map[string][]RangeColumnExpr)
 	for _, cet := range idx.ColumnExpressionTypes() {
-		colExprTypes[strings.ToLower(cet.Expression)] = cet.Type
-		ranges[strings.ToLower(cet.Expression)] = []RangeColumnExpr{AllRangeColumnExpr(cet.Type)}
+		typ := cet.Type
+		if _, ok := typ.(StringType); ok {
+			typ = typ.Promote()
+		}
+		colExprTypes[strings.ToLower(cet.Expression)] = typ
+		ranges[strings.ToLower(cet.Expression)] = []RangeColumnExpr{AllRangeColumnExpr(typ)}
 	}
 	return &IndexBuilder{
 		idx:          idx,
@@ -128,13 +132,14 @@ func (b *IndexBuilder) Equals(ctx *Context, colExpr string, keys ...interface{})
 			}
 		}
 
-		res, _, err := typ.Convert(k)
+		var err error
+		k, _, err = typ.Convert(k)
 		if err != nil {
 			b.isInvalid = true
 			b.err = err
 			return b
 		}
-		potentialRanges[i] = ClosedRangeColumnExpr(res, res, typ)
+		potentialRanges[i] = ClosedRangeColumnExpr(k, k, typ)
 	}
 	b.updateCol(ctx, colExpr, potentialRanges...)
 	return b
@@ -151,7 +156,6 @@ func (b *IndexBuilder) NotEquals(ctx *Context, colExpr string, key interface{})
 		b.err = ErrInvalidColExpr.New(colExpr, b.idx.ID())
 		return b
 	}
-
 	// if converting from float to int results in rounding, then it's entire range (excluding nulls)
 	f, c := floor(key), ceil(key)
 	switch key.(type) {
@@ -275,7 +279,6 @@ func (b *IndexBuilder) LessThan(ctx *Context, colExpr string, key interface{}) *
 	if t, ok := typ.(NumberType); ok && !t.IsFloat() {
 		key = ceil(key)
 	}
-
 	key, _, err := typ.Convert(key)
 	if err != nil {
 		b.isInvalid = true
@@ -371,7 +374,11 @@ func (b *IndexBuilder) Ranges(ctx *Context) RangeCollection {
 		cets := b.idx.ColumnExpressionTypes()
 		emptyRange := make(Range, len(cets))
 		for i, cet := range cets {
-			emptyRange[i] = EmptyRangeColumnExpr(cet.Type)
+			typ := cet.Type
+			if _, ok := typ.(StringType); ok {
+				typ = typ.Promote()
+			}
+			emptyRange[i] = EmptyRangeColumnExpr(typ)
 		}
 		return RangeCollection{emptyRange}
 	}
@@ -421,7 +428,7 @@ func (b *IndexBuilder) Ranges(ctx *Context) RangeCollection {
 		cets := b.idx.ColumnExpressionTypes()
 		emptyRange := make(Range, len(cets))
 		for i, cet := range cets {
-			emptyRange[i] = EmptyRangeColumnExpr(cet.Type)
+			emptyRange[i] = EmptyRangeColumnExpr(cet.Type.Promote())
 		}
 		return RangeCollection{emptyRange}
 	}
diff --git a/sql/range.go b/sql/range.go
index ab11dde4f6..a990b5352a 100644
--- a/sql/range.go
+++ b/sql/range.go
@@ -223,6 +223,9 @@ func (rang Range) TryMerge(otherRange Range) (Range, bool, error) {
 			}
 		}
 	}
+	if indexToMerge == -1 {
+		return nil, false, fmt.Errorf("invalid index to merge")
+	}
 	mergedLastExpr, ok, err := rang[indexToMerge].TryUnion(otherRange[indexToMerge])
 	if err != nil || !ok {
 		return nil, false, err