fix: read default for the data insert before first instant (#48)

Author: WinChua

devtools/create_instant_table.py

@@ -37,4 +37,13 @@
     conn.exec_driver_sql('''
 alter table test_for_instant add column drop1 int(11) not null default '99'
 ''')
-
+    conn.exec_driver_sql('''
+insert into test_for_instant (name, drop1, drop2, add2) values ('insert after first add', 23, 'drop2 after first add', 'add2')
+''')
+    conn.exec_driver_sql('''
+alter table test_for_instant add column add3 varchar(255) not null 
+''')
+    conn.exec_driver_sql('''
+insert into test_for_instant (name, drop1, drop2, add2, add3) values ('insert after second add', 23, 'drop2 after second add', 'add2', 'add3')
+''')
+    conn.commit()

src/pyinnodb/disk_struct/index.py

@@ -132,9 +132,9 @@ def value_parser(rh: MRecordHeader, f):
             if rh.instant == 1:
                 f.seek(-1, 1)
                 extra_byte = int.from_bytes(f.read(1), "big")
+                cols_disk_layout = cols_disk_layout[:extra_byte]
                 logger.debug("instant col extra byte is %s, &0x80 is %s, len(cols) is %d", hex(extra_byte), extra_byte & 0x80, 
                         len(cols_disk_layout))
-                cols_disk_layout = cols_disk_layout[:extra_byte]
 
             nullable_cols = [d[0] for d in cols_disk_layout if d[1] == 4294967295 and d[0].is_nullable]
 
@@ -143,8 +143,8 @@ def value_parser(rh: MRecordHeader, f):
 
 
             if rh.instant == 0 and rh.instant_version == 0:
-                nullable_cols = [c for c in nullable_cols if "default_null" not in c.se_private_data]
-                cols_disk_layout = [d for d in cols_disk_layout if "default_null" not in d[0].se_private_data]
+                nullable_cols = [c for c in nullable_cols if not c.is_instant_col_80017]
+                cols_disk_layout = [d for d in cols_disk_layout if not d[0].is_instant_col_80017]
 
             nullcol_bitmask_size = int((len(nullable_cols) + 7) / 8)
             f.seek(-nullcol_bitmask_size - rh.instant_version - rh.instant, 1)

src/pyinnodb/sdi/table.py

@@ -169,7 +169,11 @@ def is_hidden_from_user(self):
     @cache
     def is_instant_col(self):
         return "version_added" in self.private_data or "version_dropped" in self.private_data
-        #return "default_null" in self.private_data or "default" in self.private_data
+
+    @property
+    @cache
+    def is_instant_col_80017(self):
+        return "default_null" in self.private_data or "default" in self.private_data
 
     def get_instant_default(self):
         # if self.default_value_utf8_null: