evalengine: disable the static IN hash table for JSON operands

Signed-off-by: Graham Campbell <hello@gjcampbell.co.uk>

Author: GrahamCampbell

go/vt/vtgate/evalengine/compiler_test.go

@@ -918,6 +918,29 @@ func TestJSONComparisonDomains(t *testing.T) {
 		{expression: `'[]' IN (JSON_ARRAY(), '0')`, result: `INT64(0)`},
 		{expression: `'0' IN (CAST('[]' AS JSON), '0')`, result: `INT64(1)`},
 
+		// JSON arrays and objects hash by kind and cardinality only: IN
+		// must compare them for real instead of trusting a hash hit.
+		{
+			expression: `column0 IN (JSON_ARRAY(2))`,
+			values:     []sqltypes.Value{sqltypes.MakeTrusted(sqltypes.TypeJSON, []byte(`[1]`))},
+			result:     `INT64(0)`,
+		},
+		{
+			expression: `column0 IN (JSON_OBJECT('b', 2))`,
+			values:     []sqltypes.Value{sqltypes.MakeTrusted(sqltypes.TypeJSON, []byte(`{"a": 1}`))},
+			result:     `INT64(0)`,
+		},
+		{
+			expression: `column0 IN (JSON_ARRAY(1))`,
+			values:     []sqltypes.Value{sqltypes.MakeTrusted(sqltypes.TypeJSON, []byte(`[1]`))},
+			result:     `INT64(1)`,
+		},
+		{
+			expression: `column0 IN (JSON_OBJECT('a', 1))`,
+			values:     []sqltypes.Value{sqltypes.MakeTrusted(sqltypes.TypeJSON, []byte(`{"a": 1}`))},
+			result:     `INT64(1)`,
+		},
+
 		// ENUM and SET values convert to JSON string scalars of their
 		// textual value when a JSON value participates in the IN domain.
 		{

go/vt/vtgate/evalengine/expr_compare.go

@@ -727,6 +727,13 @@ func (i *InExpr) eval(env *ExpressionEnv) (eval, error) {
 }
 
 func (i *InExpr) compileTable(lhs ctype, rhs TupleExpr) map[vthash.Hash]struct{} {
+	// JSON hashes fingerprint arrays and objects by kind and cardinality
+	// only: a hash hit is not equality, so JSON stays on the comparing
+	// slow path.
+	if lhs.Type == sqltypes.TypeJSON {
+		return nil
+	}
+
 	var (
 		table  = make(map[vthash.Hash]struct{})
 		hasher = vthash.New()