merge of 2876.430.11 & 2876.430.1

CF_PREOPEN_TMP_TABLES & CF_HA_CLOSE & Patch for Bug#11746602 (27480: Extend CREATE TEMPORARY TABLES 
  privilege to allow temp table operations).

sql/sql_acl.cc

@@ -4643,6 +4643,7 @@ bool check_grant(THD *thd, ulong want_access, TABLE_LIST *tables,
         Note that during creation of temporary table we still need to check
         if user has CREATE_TMP_ACL.
       */
+      tl->grant.privilege|= TMP_TABLE_ACLS;
       tl->grant.want_privilege= 0;
       continue;
     }

sql/sql_admin.cc

@@ -122,8 +122,7 @@ static int prepare_for_repair(THD *thd, TABLE_LIST *table_list,
                                  MDL_EXCLUSIVE, MDL_TRANSACTION);
 
     if (lock_table_names(thd, table_list, table_list->next_global,
-                         thd->variables.lock_wait_timeout,
-                         MYSQL_OPEN_SKIP_TEMPORARY))
+                         thd->variables.lock_wait_timeout, 0))
       DBUG_RETURN(0);
     has_mdl_lock= TRUE;
 

sql/sql_base.cc

@@ -2276,14 +2276,15 @@ TABLE *find_temporary_table(THD *thd,
 
 int drop_temporary_table(THD *thd, TABLE_LIST *table_list, bool *is_trans)
 {
-  TABLE *table;
   DBUG_ENTER("drop_temporary_table");
   DBUG_PRINT("tmptable", ("closing table: '%s'.'%s'",
                           table_list->db, table_list->table_name));
 
-  if (!(table= find_temporary_table(thd, table_list)))
+  if (!is_temporary_table(table_list))
     DBUG_RETURN(1);
 
+  TABLE *table= table_list->table;
+
   /* Table might be in use by some outer statement. */
   if (table->query_id && table->query_id != thd->query_id)
   {
@@ -2291,7 +2292,6 @@ int drop_temporary_table(THD *thd, TABLE_LIST *table_list, bool *is_trans)
     DBUG_RETURN(-1);
   }
 
-  if (is_trans != NULL)
   *is_trans= table->file->has_transactions();
 
   /*
@@ -2300,6 +2300,7 @@ int drop_temporary_table(THD *thd, TABLE_LIST *table_list, bool *is_trans)
   */
   mysql_lock_remove(thd, thd->lock, table);
   close_temporary_table(thd, table, 1, 1);
+  table_list->table= NULL;
   DBUG_RETURN(0);
 }
 
@@ -4238,8 +4239,7 @@ recover_from_failed_open(THD *thd)
     case OT_DISCOVER:
       {
         if ((result= lock_table_names(thd, m_failed_table, NULL,
-                                      get_timeout(),
-                                      MYSQL_OPEN_SKIP_TEMPORARY)))
+                                      get_timeout(), 0)))
           break;
 
         tdc_remove_table(thd, TDC_RT_REMOVE_ALL, m_failed_table->db,
@@ -4255,8 +4255,7 @@ recover_from_failed_open(THD *thd)
     case OT_REPAIR:
       {
         if ((result= lock_table_names(thd, m_failed_table, NULL,
-                                      get_timeout(),
-                                      MYSQL_OPEN_SKIP_TEMPORARY)))
+                                      get_timeout(), 0)))
           break;
 
         tdc_remove_table(thd, TDC_RT_REMOVE_ALL, m_failed_table->db,

sql/sql_base.h

@@ -93,7 +93,7 @@ TABLE *open_ltable(THD *thd, TABLE_LIST *table_list, thr_lock_type update,
 /* mysql_lock_tables() and open_table() flags bits */
 #define MYSQL_OPEN_IGNORE_GLOBAL_READ_LOCK      0x0001
 #define MYSQL_OPEN_IGNORE_FLUSH                 0x0002
-#define MYSQL_OPEN_TEMPORARY_ONLY               0x0004
+/* MYSQL_OPEN_TEMPORARY_ONLY (0x0004) is not used anymore. */
 #define MYSQL_LOCK_IGNORE_GLOBAL_READ_ONLY      0x0008
 #define MYSQL_LOCK_LOG_TABLE                    0x0010
 /**
@@ -106,8 +106,7 @@ TABLE *open_ltable(THD *thd, TABLE_LIST *table_list, thr_lock_type update,
   a new instance of the table.
 */
 #define MYSQL_OPEN_GET_NEW_TABLE                0x0040
-/** Don't look up the table in the list of temporary tables. */
-#define MYSQL_OPEN_SKIP_TEMPORARY               0x0080
+/* 0x0080 used to be MYSQL_OPEN_SKIP_TEMPORARY */
 /** Fail instead of waiting when conficting metadata lock is discovered. */
 #define MYSQL_OPEN_FAIL_ON_MDL_CONFLICT         0x0100
 /** Open tables using MDL_SHARED lock instead of one specified in parser. */
@@ -140,7 +139,6 @@ TABLE *open_ltable(THD *thd, TABLE_LIST *table_list, thr_lock_type update,
                             MYSQL_LOCK_IGNORE_GLOBAL_READ_ONLY |\
                             MYSQL_LOCK_IGNORE_TIMEOUT |\
                             MYSQL_OPEN_GET_NEW_TABLE |\
-                            MYSQL_OPEN_SKIP_TEMPORARY |\
                             MYSQL_OPEN_HAS_MDL_LOCK)
 
 bool open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,

sql/sql_db.cc

@@ -815,7 +815,7 @@ bool mysql_rm_db(THD *thd,char *db,bool if_exists, bool silent)
 
   /* Lock all tables and stored routines about to be dropped. */
   if (lock_table_names(thd, tables, NULL, thd->variables.lock_wait_timeout,
-                       MYSQL_OPEN_SKIP_TEMPORARY) ||
+                       0) ||
       lock_db_routines(thd, db))
     goto exit;
 

sql/sql_insert.cc

@@ -3918,10 +3918,10 @@ static TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info,
         {
           /*
             This shouldn't happen as creation of temporary table should make
-            it preparable for open. But let us do close_temporary_table() here
-            just in case.
+            it preparable for open. Anyway we can't drop temporary table if
+            we are unable to find it.
           */
-          drop_temporary_table(thd, create_table, NULL);
+          DBUG_ASSERT(0);
         }
         else
           table= create_table->table;

sql/sql_parse.cc

@@ -24,7 +24,7 @@
                               // set_handler_table_locks,
                               // lock_global_read_lock,
                               // make_global_read_lock_block_commit
-#include "sql_base.h"         // find_temporary_tablesx
+#include "sql_base.h"         // find_temporary_table
 #include "sql_cache.h"        // QUERY_CACHE_FLAGS_SIZE, query_cache_*
 #include "sql_show.h"         // mysqld_list_*, mysqld_show_*,
                               // calc_sum_of_all_status
@@ -44,7 +44,6 @@
 #include "sql_table.h"        // mysql_create_like_table,
                               // mysql_create_table,
                               // mysql_alter_table,
-                              // mysql_recreate_table,
                               // mysql_backup_table,
                               // mysql_restore_table
 #include "sql_reload.h"       // reload_acl_and_cache
@@ -124,6 +123,7 @@ static void sql_kill(THD *thd, ulong id, killed_state state);
 static void sql_kill_user(THD *thd, LEX_USER *user, killed_state state);
 static bool execute_show_status(THD *, TABLE_LIST *);
 static bool execute_rename_table(THD *, TABLE_LIST *, TABLE_LIST *);
+static bool lock_tables_precheck(THD *thd, TABLE_LIST *tables);
 
 const char *any_db="*any*";	// Special symbol for check_access
 
@@ -499,6 +499,7 @@ void init_update_queries(void)
   sql_command_flags[SQLCOM_SELECT]|=          CF_PREOPEN_TMP_TABLES;
   sql_command_flags[SQLCOM_SET_OPTION]|=      CF_PREOPEN_TMP_TABLES;
   sql_command_flags[SQLCOM_DO]|=              CF_PREOPEN_TMP_TABLES;
+  sql_command_flags[SQLCOM_HA_OPEN]|=         CF_PREOPEN_TMP_TABLES;
   sql_command_flags[SQLCOM_CALL]|=            CF_PREOPEN_TMP_TABLES;
   sql_command_flags[SQLCOM_CHECKSUM]|=        CF_PREOPEN_TMP_TABLES;
   sql_command_flags[SQLCOM_ANALYZE]|=         CF_PREOPEN_TMP_TABLES;
@@ -2413,6 +2414,7 @@ mysql_execute_command(THD *thd)
     if (open_temporary_tables(thd, all_tables))
       goto error;
   }
+
   switch (lex->sql_command) {
 
   case SQLCOM_SHOW_EVENTS:
@@ -2422,8 +2424,7 @@ mysql_execute_command(THD *thd)
 #endif
   case SQLCOM_SHOW_STATUS_PROC:
   case SQLCOM_SHOW_STATUS_FUNC:
-    if ((res= check_table_access(thd, SELECT_ACL, all_tables, FALSE,
-                                  UINT_MAX, FALSE)))
+    if (lock_tables_precheck(thd, all_tables))
       goto error;
     res= execute_sqlcom_select(thd, all_tables);
     break;
@@ -2798,12 +2799,6 @@ case SQLCOM_PREPARE:
     }
 #endif
 
-    /*
-      Close any open handlers for the table. We need to this extra call here
-      as there may have been new handlers created since the previous call.
-     */
-    mysql_ha_rm_tables(thd, create_table);
-
     if (select_lex->item_list.elements)		// With select
     {
       select_result *result;
@@ -4173,6 +4168,9 @@ end_with_restore_list:
     DBUG_ASSERT(first_table == all_tables && first_table != 0);
     if (check_table_access(thd, SELECT_ACL, all_tables, FALSE, UINT_MAX, FALSE))
       goto error;
+    /* Close temporary tables which were pre-opened for privilege checking. */
+    close_thread_tables(thd);
+    all_tables->table= NULL;
     res= mysql_ha_open(thd, first_table, 0);
     break;
   case SQLCOM_HA_CLOSE:
@@ -5519,6 +5517,9 @@ static bool check_show_access(THD *thd, TABLE_LIST *table)
     if (check_grant(thd, SELECT_ACL, dst_table, TRUE, UINT_MAX, FALSE))
       return TRUE; /* Access denied */
 
+    close_thread_tables(thd);
+    dst_table->table= NULL;
+
     /* Access granted */
     return FALSE;
   }
@@ -5604,10 +5605,10 @@ check_table_access(THD *thd, ulong requirements,TABLE_LIST *tables,
 
     DBUG_PRINT("info", ("derived: %d  view: %d", tables->derived != 0,
                         tables->view != 0));
-    if (tables->is_anonymous_derived_table() ||
-        (tables->table && tables->table->s &&
-         (int)tables->table->s->tmp_table))
+
+    if (tables->is_anonymous_derived_table())
       continue;
+
     thd->security_ctx= sctx;
 
     if (check_access(thd, want_access, tables->get_db_name(),
@@ -7465,6 +7466,19 @@ bool multi_delete_precheck(THD *thd, TABLE_LIST *tables)
   TABLE_LIST **save_query_tables_own_last= thd->lex->query_tables_own_last;
   DBUG_ENTER("multi_delete_precheck");
 
+  /*
+    Temporary tables are pre-opened in 'tables' list only. Here we need to
+    initialize TABLE instances in 'aux_tables' list.
+  */
+  for (TABLE_LIST *tl= aux_tables; tl; tl= tl->next_global)
+  {
+    if (tl->table)
+      continue;
+
+    if (tl->correspondent_table)
+      tl->table= tl->correspondent_table->table;
+  }
+
   /* sql_yacc guarantees that tables and aux_tables are not zero */
   DBUG_ASSERT(aux_tables != 0);
   if (check_table_access(thd, SELECT_ACL, tables, FALSE, UINT_MAX, FALSE))
@@ -7733,9 +7747,9 @@ bool create_table_precheck(THD *thd, TABLE_LIST *tables,
     CREATE TABLE ... SELECT, also require INSERT.
   */
 
-  want_priv= ((lex->create_info.options & HA_LEX_CREATE_TMP_TABLE) ?
-              CREATE_TMP_ACL : CREATE_ACL) |
-             (select_lex->item_list.elements ? INSERT_ACL : 0);
+  want_priv= (lex->create_info.options & HA_LEX_CREATE_TMP_TABLE) ?
+             CREATE_TMP_ACL :
+             (CREATE_ACL | (select_lex->item_list.elements ? INSERT_ACL : 0));
 
   if (check_access(thd, want_priv, create_table->db,
                    &create_table->grant.privilege,
@@ -7744,11 +7758,48 @@ bool create_table_precheck(THD *thd, TABLE_LIST *tables,
     goto err;
 
   /* If it is a merge table, check privileges for merge children. */
-  if (lex->create_info.merge_list.first &&
-      check_table_access(thd, SELECT_ACL | UPDATE_ACL | DELETE_ACL,
+  if (lex->create_info.merge_list.first)
+  {
+    /*
+      The user must have (SELECT_ACL | UPDATE_ACL | DELETE_ACL) on the
+      underlying base tables, even if there are temporary tables with the same
+      names.
+
+      From user's point of view, it might look as if the user must have these
+      privileges on temporary tables to create a merge table over them. This is
+      one of two cases when a set of privileges is required for operations on
+      temporary tables (see also CREATE TABLE).
+
+      The reason for this behavior stems from the following facts:
+
+        - For merge tables, the underlying table privileges are checked only
+          at CREATE TABLE / ALTER TABLE time.
+
+          In other words, once a merge table is created, the privileges of
+          the underlying tables can be revoked, but the user will still have
+          access to the merge table (provided that the user has privileges on
+          the merge table itself). 
+
+        - Temporary tables shadow base tables.
+
+          I.e. there might be temporary and base tables with the same name, and
+          the temporary table takes the precedence in all operations.
+
+        - For temporary MERGE tables we do not track if their child tables are
+          base or temporary. As result we can't guarantee that privilege check
+          which was done in presence of temporary child will stay relevant later
+          as this temporary table might be removed.
+
+      If SELECT_ACL | UPDATE_ACL | DELETE_ACL privileges were not checked for
+      the underlying *base* tables, it would create a security breach as in
+      Bug#12771903.
+    */
+
+    if (check_table_access(thd, SELECT_ACL | UPDATE_ACL | DELETE_ACL,
                            lex->create_info.merge_list.first,
                            FALSE, UINT_MAX, FALSE))
       goto err;
+  }
 
   if (want_priv != CREATE_TMP_ACL &&
       check_grant(thd, want_priv, create_table, FALSE, 1, FALSE))
@@ -7773,6 +7824,35 @@ err:
 }
 
 
+/**
+  Check privileges for LOCK TABLES statement.
+
+  @param thd     Thread context.
+  @param tables  List of tables to be locked.
+
+  @retval FALSE - Success.
+  @retval TRUE  - Failure.
+*/
+
+static bool lock_tables_precheck(THD *thd, TABLE_LIST *tables)
+{
+  TABLE_LIST *first_not_own_table= thd->lex->first_not_own_table();
+
+  for (TABLE_LIST *table= tables; table != first_not_own_table && table;
+       table= table->next_global)
+  {
+    if (is_temporary_table(table))
+      continue;
+
+    if (check_table_access(thd, LOCK_TABLES_ACL | SELECT_ACL, table,
+                           FALSE, 1, FALSE))
+      return TRUE;
+  }
+
+  return FALSE;
+}
+
+
 /**
   negate given expression.
 

sql/sql_prepare.cc

@@ -106,6 +106,7 @@ When one supplies long data for a placeholder:
 #include "sp_head.h"
 #include "sp.h"
 #include "sp_cache.h"
+#include "sql_handler.h"  // mysql_ha_rm_tables
 #include "probes_mysql.h"
 #ifdef EMBEDDED_LIBRARY
 /* include MYSQL_BIND headers */

sql/sql_rename.cc

@@ -142,7 +142,7 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list, bool silent)
   }
 
   if (lock_table_names(thd, table_list, 0, thd->variables.lock_wait_timeout,
-                       MYSQL_OPEN_SKIP_TEMPORARY))
+                       0))
     goto err;
 
   for (ren_table= table_list; ren_table; ren_table= ren_table->next_local)

sql/sql_table.cc

@@ -2073,14 +2073,12 @@ bool mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists,
     }
   }
 
-  mysql_ha_rm_tables(thd, tables);
-
   if (!drop_temporary)
   {
     if (!thd->locked_tables_mode)
     {
-      if (lock_table_names(thd, tables, NULL, thd->variables.lock_wait_timeout,
-                           MYSQL_OPEN_SKIP_TEMPORARY))
+      if (lock_table_names(thd, tables, NULL,
+                           thd->variables.lock_wait_timeout, 0))
         DBUG_RETURN(true);
       for (table= tables; table; table= table->next_local)
       {
@@ -2206,6 +2204,9 @@ static uint32 comment_length(THD *thd, uint32 comment_pos,
   @note This function assumes that metadata locks have already been taken.
         It is also assumed that the tables have been removed from TDC.
 
+  @note This function assumes that temporary tables to be dropped have
+        been pre-opened using corresponding table list elements.
+
   @todo When logging to the binary log, we should log
         tmp_tables and transactional tables as separate statements if we
         are in a transaction;  This is needed to get these tables into the
@@ -5060,6 +5061,7 @@ bool mysql_create_like_table(THD* thd, TABLE_LIST* table, TABLE_LIST* src_table,
         String query(buf, sizeof(buf), system_charset_info);
         query.length(0);  // Have to zero it since constructor doesn't
         Open_table_context ot_ctx(thd, MYSQL_OPEN_REOPEN);
+        bool new_table= FALSE; // Whether newly created table is open.
 
         /*
           The condition avoids a crash as described in BUG#48506. Other
@@ -5068,14 +5070,21 @@ bool mysql_create_like_table(THD* thd, TABLE_LIST* table, TABLE_LIST* src_table,
         */
         if (!table->view)
         {
+          if (!table->table)
+          {
+
             /*
-            Here we open the destination table, on which we already have
-            exclusive metadata lock. This is needed for store_create_info()
-            to work. The table will be closed by close_thread_table() at
-            the end of this branch.
+              In order for store_create_info() to work we need to open
+              destination table if it is not already open (i.e. if it
+              has not existed before). We don't need acquire metadata
+              lock in order to do this as we already hold exclusive
+              lock on this table. The table will be closed by
+              close_thread_table() at the end of this branch.
             */
             if (open_table(thd, table, thd->mem_root, &ot_ctx))
               goto err;
+            new_table= TRUE;
+          }
 
           int result __attribute__((unused))=
             store_create_info(thd, table, &query,
@@ -5085,15 +5094,18 @@ bool mysql_create_like_table(THD* thd, TABLE_LIST* table, TABLE_LIST* src_table,
           if (write_bin_log(thd, TRUE, query.ptr(), query.length()))
             goto err;
 
+          if (new_table)
+          {
             DBUG_ASSERT(thd->open_tables == table->table);
             /*
               When opening the table, we ignored the locked tables
-            (MYSQL_OPEN_GET_NEW_TABLE). Now we can close the table without
-            risking to close some locked table.
+              (MYSQL_OPEN_GET_NEW_TABLE). Now we can close the table
+              without risking to close some locked table.
             */
             close_thread_table(thd, &thd->open_tables);
           }
         }
+      }
       else                                      // Case 1
         if (write_bin_log(thd, TRUE, thd->query(), thd->query_length()))
           goto err;
@@ -8821,11 +8833,6 @@ bool mysql_checksum_table(THD *thd, TABLE_LIST *tables,
       if (! thd->in_sub_stmt)
         trans_rollback_stmt(thd);
       close_thread_tables(thd);
-      /*
-        Don't release metadata locks, this will be done at
-        statement end.
-      */
-      table->table=0;				// For query cache
     }
     if (protocol->write())
       goto err;

sql/sql_truncate.cc

@@ -18,9 +18,8 @@
 #include "sql_class.h"   // THD
 #include "sql_base.h"    // open_and_lock_tables
 #include "sql_table.h"   // write_bin_log
-#include "sql_handler.h" // mysql_ha_rm_tables
 #include "datadict.h"    // dd_recreate_table()
-#include "lock.h"        // MYSQL_OPEN_TEMPORARY_ONLY
+#include "lock.h"        // MYSQL_OPEN_* flags
 #include "sql_acl.h"     // DROP_ACL
 #include "sql_parse.h"   // check_one_table_access()
 #include "sql_truncate.h"
@@ -199,9 +198,7 @@ int Sql_cmd_truncate_table::handler_truncate(THD *thd, TABLE_LIST *table_ref,
   */
 
   /* If it is a temporary table, no need to take locks. */
-  if (is_tmp_table)
-    flags= MYSQL_OPEN_TEMPORARY_ONLY;
-  else
+  if (!is_tmp_table)
   {
     /* We don't need to load triggers. */
     DBUG_ASSERT(table_ref->trg_event_map == 0);
@@ -216,7 +213,7 @@ int Sql_cmd_truncate_table::handler_truncate(THD *thd, TABLE_LIST *table_ref,
       the MDL lock taken above and otherwise there is no way to
       wait for FLUSH TABLES in deadlock-free fashion.
     */
-    flags= MYSQL_OPEN_IGNORE_FLUSH | MYSQL_OPEN_SKIP_TEMPORARY;
+    flags= MYSQL_OPEN_IGNORE_FLUSH;
     /*
       Even though we have an MDL lock on the table here, we don't
       pass MYSQL_OPEN_HAS_MDL_LOCK to open_and_lock_tables
@@ -346,8 +343,7 @@ bool Sql_cmd_truncate_table::lock_table(THD *thd, TABLE_LIST *table_ref,
     /* Acquire an exclusive lock. */
     DBUG_ASSERT(table_ref->next_global == NULL);
     if (lock_table_names(thd, table_ref, NULL,
-                         thd->variables.lock_wait_timeout,
-                         MYSQL_OPEN_SKIP_TEMPORARY))
+                         thd->variables.lock_wait_timeout, 0))
       DBUG_RETURN(TRUE);
 
     if (dd_check_storage_engine_flag(thd, table_ref->db, table_ref->table_name,
@@ -399,26 +395,28 @@ bool Sql_cmd_truncate_table::lock_table(THD *thd, TABLE_LIST *table_ref,
 bool Sql_cmd_truncate_table::truncate_table(THD *thd, TABLE_LIST *table_ref)
 {
   int error;
-  TABLE *table;
   bool binlog_stmt;
   DBUG_ENTER("Sql_cmd_truncate_table::truncate_table");
 
+  DBUG_ASSERT((!table_ref->table) ||
+              (table_ref->table && table_ref->table->s));
+
   /* Initialize, or reinitialize in case of reexecution (SP). */
   m_ticket_downgrade= NULL;
 
-  /* Remove table from the HANDLER's hash. */
-  mysql_ha_rm_tables(thd, table_ref);
-
   /* If it is a temporary table, no need to take locks. */
-  if ((table= find_temporary_table(thd, table_ref)))
+  if (is_temporary_table(table_ref))
   {
+    TABLE *tmp_table= table_ref->table;
+
     /* In RBR, the statement is not binlogged if the table is temporary. */
     binlog_stmt= !thd->is_current_stmt_binlog_format_row();
 
     /* Note that a temporary table cannot be partitioned. */
-    if (ha_check_storage_engine_flag(table->s->db_type(), HTON_CAN_RECREATE))
+    if (ha_check_storage_engine_flag(tmp_table->s->db_type(),
+                                     HTON_CAN_RECREATE))
     {
-      if ((error= recreate_temporary_table(thd, table)))
+      if ((error= recreate_temporary_table(thd, tmp_table)))
         binlog_stmt= FALSE; /* No need to binlog failed truncate-by-recreate. */
 
       DBUG_ASSERT(! thd->transaction.stmt.modified_non_trans_table);

sql/sql_view.cc

@@ -1665,8 +1665,7 @@ bool mysql_drop_view(THD *thd, TABLE_LIST *views, enum_drop_mode drop_mode)
     DBUG_RETURN(TRUE);
   }
 
-  if (lock_table_names(thd, views, 0, thd->variables.lock_wait_timeout,
-                       MYSQL_OPEN_SKIP_TEMPORARY))
+  if (lock_table_names(thd, views, 0, thd->variables.lock_wait_timeout, 0))
     DBUG_RETURN(TRUE);
 
   for (view= views; view; view= view->next_local)

storage/myisammrg/ha_myisammrg.cc

@@ -484,6 +484,11 @@ int ha_myisammrg::add_children_list(void)
     /* Set the expected table version, to not cause spurious re-prepare. */
     child_l->set_table_ref_id(mrg_child_def->get_child_table_ref_type(),
                               mrg_child_def->get_child_def_version());
+    /*
+      Copy parent's prelocking attribute to allow opening of child
+      temporary residing in the prelocking list.
+    */
+    child_l->prelocking_placeholder= parent_l->prelocking_placeholder;
     /*
       For statements which acquire a SNW metadata lock on a parent table and
       then later try to upgrade it to an X lock (e.g. ALTER TABLE), SNW