Updated IsNullable for all functions to match Eval output

enginetest/queries/script_queries.go

@@ -9642,9 +9642,9 @@ where
 			{
 				Query: "describe t;",
 				Expected: []sql.Row{
-					{"port1", "bigint", "NO", "", nil, ""},
-					{"port2", "bigint", "NO", "", nil, ""},
-					{"port3", "bigint", "NO", "", nil, ""},
+					{"port1", "bigint", "YES", "", nil, ""},
+					{"port2", "bigint", "YES", "", nil, ""},
+					{"port3", "bigint", "YES", "", nil, ""},
 				},
 			},
 		},

sql/expression/arithmetic.go

@@ -114,7 +114,8 @@ func (a *Arithmetic) DebugString() string {
 
 // IsNullable implements the sql.Expression interface.
 func (a *Arithmetic) IsNullable() bool {
-	if types.IsDatetimeType(a.Type()) || types.IsTimestampType(a.Type()) {
+	typ := a.Type()
+	if types.IsDatetimeType(typ) || types.IsTimestampType(typ) {
 		return true
 	}
 

sql/expression/collatedexpr.go

@@ -35,7 +35,7 @@ var _ sql.CollationCoercible = (*CollatedExpression)(nil)
 var _ sql.DebugStringer = (*CollatedExpression)(nil)
 
 // NewCollatedExpression creates a new CollatedExpression expression. If the given expression is already a
-// CollatedExpression, then the previous collation is overriden with the given one.
+// CollatedExpression, then the previous collation is overridden with the given one.
 func NewCollatedExpression(expr sql.Expression, collation sql.CollationID) *CollatedExpression {
 	if collatedExpr, ok := expr.(*CollatedExpression); ok {
 		return &CollatedExpression{

sql/expression/comparison.go

@@ -529,6 +529,11 @@ func (e *NullSafeEquals) Eval(ctx *sql.Context, row sql.Row) (interface{}, error
 	return result == 0, nil
 }
 
+// IsNullable implements sql.Expression
+func (e *NullSafeEquals) IsNullable() bool {
+	return false
+}
+
 // WithChildren implements the Expression interface.
 func (e *NullSafeEquals) WithChildren(children ...sql.Expression) (sql.Expression, error) {
 	if len(children) != 2 {

sql/expression/convert.go

@@ -147,7 +147,7 @@ func GetConvertToType(l, r sql.Type) string {
 // IsNullable implements the Expression interface.
 func (c *Convert) IsNullable() bool {
 	switch c.castToType {
-	case ConvertToDate, ConvertToDatetime:
+	case ConvertToDate, ConvertToDatetime, ConvertToBinary, ConvertToChar, ConvertToNChar:
 		return true
 	default:
 		return c.Child.IsNullable()

sql/expression/distinct.go

@@ -97,7 +97,7 @@ func (de *DistinctExpression) CollationCoercibility(ctx *sql.Context) (collation
 }
 
 func (de *DistinctExpression) IsNullable() bool {
-	return false
+	return true
 }
 
 // Returns the child value if the cache hasn't seen the value before otherwise returns nil.

sql/expression/div.go

@@ -76,7 +76,7 @@ func (d *Div) DebugString() string {
 
 // IsNullable implements the sql.Expression interface.
 func (d *Div) IsNullable() bool {
-	return d.BinaryExpressionStub.IsNullable()
+	return true
 }
 
 // Type returns the result type for this division expression. For nested division expressions, we prefer sending
@@ -656,7 +656,7 @@ func (i *IntDiv) DebugString() string {
 
 // IsNullable implements the sql.Expression interface.
 func (i *IntDiv) IsNullable() bool {
-	return i.BinaryExpressionStub.IsNullable()
+	return true
 }
 
 // Type returns the greatest type for given operation.

sql/expression/function/absval.go

@@ -108,6 +108,10 @@ func (t *AbsVal) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
 		return x.Abs(), nil
 	}
 
+	// TODO: Strings should truncate to float prefix. We should also check what other types return. But abs should not
+	// return null for non-null values
+	// https://github.com/dolthub/dolt/issues/10171
+	// https://dev.mysql.com/doc/refman/8.4/en/mathematical-functions.html#function_abs
 	return nil, nil
 }
 

sql/expression/function/aggregation/group_concat.go

@@ -213,7 +213,12 @@ func (g *GroupConcat) Type() sql.Type {
 
 // IsNullable implements the Expression interface.
 func (g *GroupConcat) IsNullable() bool {
-	return false
+	for _, se := range g.selectExprs {
+		if !se.IsNullable() {
+			return false
+		}
+	}
+	return true
 }
 
 // Children implements the Expression interface.

sql/expression/function/aggregation/json_agg.go

@@ -90,7 +90,7 @@ func (*JSONObjectAgg) CollationCoercibility(ctx *sql.Context) (collation sql.Col
 
 // IsNullable implements the Expression interface.
 func (j *JSONObjectAgg) IsNullable() bool {
-	return false
+	return true
 }
 
 // Children implements the Expression interface.

sql/expression/function/aggregation/window/first_value.go

@@ -104,7 +104,7 @@ func (f *FirstValue) CollationCoercibility(ctx *sql.Context) (collation sql.Coll
 
 // IsNullable implements sql.Expression
 func (f *FirstValue) IsNullable() bool {
-	return false
+	return f.Child.IsNullable()
 }
 
 // Eval implements sql.Expression

sql/expression/function/aggregation/window/last_value.go

@@ -104,7 +104,7 @@ func (f *LastValue) CollationCoercibility(ctx *sql.Context) (collation sql.Colla
 
 // IsNullable implements sql.Expression
 func (f *LastValue) IsNullable() bool {
-	return false
+	return f.Child.IsNullable()
 }
 
 // Eval implements sql.Expression

sql/expression/function/ceil_round_floor.go

@@ -325,7 +325,7 @@ func (r *Round) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
 
 // IsNullable implements the Expression interface.
 func (r *Round) IsNullable() bool {
-	return r.Num.IsNullable() && (r == nil || r.Dec.IsNullable())
+	return r.Num.IsNullable() || (r.Dec != nil && r.Dec.IsNullable())
 }
 
 func (r *Round) String() string {