fix an old bug where dd_frm_type() could incorrectly determine the table type

for dynamic engines (because it only looked at the one-byte code, not at the full
engine name).

mysql-test/r/drop_bad_db_type.result

+set debug_dbug='+d,unstable_db_type';
+install soname 'ha_archive';
+create table t1 (a int) engine=archive;
+insert t1 values (1),(2),(3);
+flush tables;
+uninstall soname 'ha_archive';
+install soname 'ha_archive';
+t1.ARZ
+t1.frm
+drop table t1;
+uninstall soname 'ha_archive';
+set debug_dbug='-d,unstable_db_type';

mysql-test/t/drop_bad_db_type.test

+
+--source include/have_debug.inc
+
+if (!$HA_ARCHIVE_SO) {
+  skip Needs Archive plugin;
+}
+
+let $mysqld_datadir= `select @@datadir`;
+
+set debug_dbug='+d,unstable_db_type';
+
+install soname 'ha_archive';
+create table t1 (a int) engine=archive;
+insert t1 values (1),(2),(3);
+flush tables;
+uninstall soname 'ha_archive';
+
+install soname 'ha_archive';
+--list_files $mysqld_datadir/test
+drop table t1;
+--list_files $mysqld_datadir/test
+uninstall soname 'ha_archive';
+
+set debug_dbug='-d,unstable_db_type';
+

mysql-test/t/func_str.test

@@ -6,6 +6,8 @@
 drop table if exists t1,t2;
 --enable_warnings
 
+let $mysqld_datadir= `select @@datadir`;
+
 set names latin1;
 
 select 'hello',"'hello'",'""hello""','''h''e''l''l''o''',"hel""lo",'hel\'lo';
@@ -1385,6 +1387,8 @@ LOAD DATA INFILE 'bug58165.txt' INTO TABLE t1;
 SELECT * FROM t1;
 DROP TABLE t1;
 
+--remove_file $mysqld_datadir/test/bug58165.txt
+
 #
 # MDEV-759 lp:998340 - Valgrind complains on simple selects containing expression DAY(FROM_UNIXTIME(-1))
 #

sql/datadict.cc

@@ -36,6 +36,7 @@ frm_type_enum dd_frm_type(THD *thd, char *path, enum legacy_db_type *dbt)
   File file;
   uchar header[10];     //"TYPE=VIEW\n" it is 10 characters
   size_t error;
+  frm_type_enum type= FRMTYPE_ERROR;
   DBUG_ENTER("dd_frm_type");
 
   *dbt= DB_TYPE_UNKNOWN;
@@ -43,12 +44,16 @@ frm_type_enum dd_frm_type(THD *thd, char *path, enum legacy_db_type *dbt)
   if ((file= mysql_file_open(key_file_frm, path, O_RDONLY | O_SHARE, MYF(0))) < 0)
     DBUG_RETURN(FRMTYPE_ERROR);
   error= mysql_file_read(file, (uchar*) header, sizeof(header), MYF(MY_NABP));
-  mysql_file_close(file, MYF(MY_WME));
 
   if (error)
-    DBUG_RETURN(FRMTYPE_ERROR);
+    goto err;
   if (!strncmp((char*) header, "TYPE=VIEW\n", sizeof(header)))
-    DBUG_RETURN(FRMTYPE_VIEW);
+  {
+    type= FRMTYPE_VIEW;
+    goto err;
+  }
+
+  type= FRMTYPE_TABLE;
 
   /*
     This is just a check for DB_TYPE. We'll return default unknown type
@@ -58,12 +63,57 @@ frm_type_enum dd_frm_type(THD *thd, char *path, enum legacy_db_type *dbt)
   if (header[0] != (uchar) 254 || header[1] != 1 ||
       (header[2] != FRM_VER && header[2] != FRM_VER+1 &&
        (header[2] < FRM_VER+3 || header[2] > FRM_VER+4)))
-    DBUG_RETURN(FRMTYPE_TABLE);
+    goto err;
 
   *dbt= (enum legacy_db_type) (uint) *(header + 3);
 
+  if (*dbt >= DB_TYPE_FIRST_DYNAMIC) /* read the true engine name */
+  {
+    MY_STAT state;  
+    uchar *frm_image= 0;
+    uint n_length;
+
+    if (mysql_file_fstat(file, &state, MYF(MY_WME)))
+      goto err;
+
+    if (mysql_file_seek(file, 0, SEEK_SET, MYF(MY_WME)))
+      goto err;
+
+    if (read_string(file, &frm_image, state.st_size))
+      goto err;
+
+    if ((n_length= uint4korr(frm_image+55)))
+    {
+      uint record_offset= (uint2korr(frm_image+6)+
+                      ((uint2korr(frm_image+14) == 0xffff ?
+                        uint4korr(frm_image+47) : uint2korr(frm_image+14))));
+      uint reclength= uint2korr(frm_image+16);
+
+      uchar *next_chunk= frm_image + record_offset + reclength;
+      uchar *buff_end= next_chunk + n_length;
+      uint connect_string_length= uint2korr(next_chunk);
+      next_chunk+= connect_string_length + 2;
+      if (next_chunk + 2 < buff_end)
+      {
+        uint str_db_type_length= uint2korr(next_chunk);
+        LEX_STRING name;
+        name.str= (char*) next_chunk + 2;
+        name.length= str_db_type_length;
+        plugin_ref tmp_plugin= ha_resolve_by_name(thd, &name);
+        if (tmp_plugin)
+          *dbt= plugin_data(tmp_plugin, handlerton *)->db_type;
+        else
+          *dbt= DB_TYPE_UNKNOWN;
+      }
+    }
+
+    my_free(frm_image);
+  }
+
   /* Probably a table. */
-  DBUG_RETURN(FRMTYPE_TABLE);
+err:
+  mysql_file_close(file, MYF(MY_WME));
+  DBUG_RETURN(type);
 }
 
 

sql/handler.cc

@@ -486,6 +486,12 @@ int ha_initialize_handlerton(st_plugin_int *plugin)
     {
       uint tmp;
       ulong fslot;
+
+      DBUG_EXECUTE_IF("unstable_db_type", {
+                        static int i= (int) DB_TYPE_FIRST_DYNAMIC;
+                        hton->db_type= (enum legacy_db_type)++i;
+                      });
+
       /* now check the db_type for conflict */
       if (hton->db_type <= DB_TYPE_UNKNOWN ||
           hton->db_type >= DB_TYPE_DEFAULT ||