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

@@ -1129,3 +1129,69 @@ func TestCompilerNonConstant(t *testing.T) {
 		})
 	}
 }
+
+// TestJSONInStaticTable checks that IN over folded JSON literals does not
+// compile the static hash table: JSON arrays and objects hash by kind and
+// cardinality only, so a hash hit is not equality. Compilation fails until
+// the compiler learns to push JSON literals; the follow-up literal change
+// flips this test to compiled evaluation.
+func TestJSONInStaticTable(t *testing.T) {
+	testCases := []struct {
+		expression string
+		values     []sqltypes.Value
+		result     string
+	}{
+		{
+			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)`,
+		},
+	}
+
+	venv := vtenv.NewTestEnv()
+	for _, tc := range testCases {
+		t.Run(tc.expression, func(t *testing.T) {
+			expr, err := venv.Parser().ParseExpr(tc.expression)
+			require.NoError(t, err)
+
+			fields := evalengine.FieldResolver(makeFields(tc.values))
+			cfg := &evalengine.Config{
+				ResolveColumn: fields.Column,
+				Collation:     collations.CollationUtf8mb4ID,
+				Environment:   venv,
+			}
+
+			translated, err := evalengine.Translate(expr, cfg)
+			require.NoError(t, err)
+
+			untyped, ok := translated.(*evalengine.UntypedExpr)
+			require.True(t, ok)
+
+			env := evalengine.EmptyExpressionEnv(venv)
+			env.Row = tc.values
+			env.Fields = makeFields(tc.values)
+
+			res, err := env.EvaluateAST(untyped)
+			require.NoError(t, err)
+			assert.Equal(t, tc.result, res.String())
+
+			_, err = untyped.Compile(env)
+			require.ErrorContains(t, err, "unsupported literal kind")
+		})
+	}
+}

go/vt/vtgate/evalengine/expr_compare.go

@@ -531,6 +531,13 @@ 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()