Bug#49938: Failing assertion: inode or deadlock in fsp/fsp0fsp.c

Bug#54678: InnoDB, TRUNCATE, ALTER, I_S SELECT, crash or deadlock

- Incompatible change: truncate no longer resorts to a row by
row delete if the storage engine does not support the truncate
method. Consequently, the count of affected rows does not, in
any case, reflect the actual number of rows.

- Incompatible change: it is no longer possible to truncate a
table that participates as a parent in a foreign key constraint,
unless it is a self-referencing constraint (both parent and child
are in the same table). To work around this incompatible change
and still be able to truncate such tables, disable foreign checks
with SET foreign_key_checks=0 before truncate. Alternatively, if
foreign key checks are necessary, please use a DELETE statement
without a WHERE condition.

Problem description:

The problem was that for storage engines that do not support
truncate table via a external drop and recreate, such as InnoDB
which implements truncate via a internal drop and recreate, the
delete_all_rows method could be invoked with a shared metadata
lock, causing problems if the engine needed exclusive access
to some internal metadata. This problem originated with the
fact that there is no truncate specific handler method, which
ended up leading to a abuse of the delete_all_rows method that
is primarily used for delete operations without a condition.

Solution:

The solution is to introduce a truncate handler method that is
invoked when the engine does not support truncation via a table
drop and recreate. This method is invoked under a exclusive
metadata lock, so that there is only a single instance of the
table when the method is invoked.

Also, the method is not invoked and a error is thrown if
the table is a parent in a non-self-referencing foreign key
relationship. This was necessary to avoid inconsistency as
some integrity checks are bypassed. This is inline with the
fact that truncate is primarily a DDL operation that was
designed to quickly remove all data from a table.

mysql-test/suite/innodb/t/innodb-truncate.test:
  Add test cases for truncate and foreign key checks.
  Also test that InnoDB resets auto-increment on truncate.
mysql-test/suite/innodb/t/innodb.test:
  FK is not necessary, test is related to auto-increment.
  
  Update error number, truncate is no longer invoked if
  table is parent in a FK relationship.
mysql-test/suite/innodb/t/innodb_mysql.test:
  Update error number, truncate is no longer invoked if
  table is parent in a FK relationship.
  
  Use delete instead of truncate, test is used to check
  the interaction of FKs, triggers and delete.
mysql-test/suite/parts/inc/partition_check.inc:
  Fix typo.
mysql-test/suite/sys_vars/t/foreign_key_checks_func.test:
  Update error number, truncate is no longer invoked if
  table is parent in a FK relationship.
mysql-test/t/mdl_sync.test:
  Modify test case to reflect and ensure that truncate takes
  a exclusive metadata lock.
mysql-test/t/trigger-trans.test:
  Update error number, truncate is no longer invoked if
  table is parent in a FK relationship.
sql/ha_partition.cc:
  Reorganize the various truncate methods. delete_all_rows is now
  passed directly to the underlying engines, so as truncate. The
  code responsible for truncating individual partitions is moved
  to ha_partition::truncate_partition, which is invoked when a
  ALTER TABLE t1 TRUNCATE PARTITION p statement is executed.
  
  Since the partition truncate no longer can be invoked via
  delete, the bitmap operations are not necessary anymore. The
  explicit reset of the auto-increment value is also removed
  as the underlying engines are now responsible for reseting
  the value.
sql/handler.cc:
  Wire up the handler truncate method.
sql/handler.h:
  Introduce and document the truncate handler method. It assumes
  certain use cases of delete_all_rows.
  
  Add method to retrieve the list of foreign keys referencing a
  table. Method is used to avoid truncating tables that are
  parent in a foreign key relationship.
sql/share/errmsg-utf8.txt:
  Add error message for truncate and FK.
sql/sql_lex.h:
  Introduce a flag so that the partition engine can detect when
  a partition is being truncated. Used to give a special error.
sql/sql_parse.cc:
  Function mysql_truncate_table no longer exists.
sql/sql_partition_admin.cc:
  Implement the TRUNCATE PARTITION statement.
sql/sql_truncate.cc:
  Change the truncate table implementation to use the new truncate
  handler method and to not rely on row-by-row delete anymore.
  
  The truncate handler method is always invoked with a exclusive
  metadata lock. Also, it is no longer possible to truncate a
  table that is parent in some non-self-referencing foreign key.
storage/archive/ha_archive.cc:
  Rename method as the description indicates that in the future
  this could be a truncate operation.
storage/blackhole/ha_blackhole.cc:
  Implement truncate as no operation for the blackhole engine in
  order to remain compatible with older releases.
storage/federated/ha_federated.cc:
  Introduce truncate method that invokes delete_all_rows.
  This is required to support partition truncate as this
  form of truncate does not implement the drop and recreate
  protocol.
storage/heap/ha_heap.cc:
  Introduce truncate method that invokes delete_all_rows.
  This is required to support partition truncate as this
  form of truncate does not implement the drop and recreate
  protocol.
storage/ibmdb2i/ha_ibmdb2i.cc:
  Introduce truncate method that invokes delete_all_rows.
  This is required to support partition truncate as this
  form of truncate does not implement the drop and recreate
  protocol.
storage/innobase/handler/ha_innodb.cc:
  Rename delete_all_rows to truncate. InnoDB now does truncate
  under a exclusive metadata lock.
  
  Introduce and reorganize methods used to retrieve the list
  of foreign keys referenced by a or referencing a table.
storage/myisammrg/ha_myisammrg.cc:
  Introduce truncate method that invokes delete_all_rows.
  This is required in order to remain compatible with earlier
  releases where truncate would resort to a row-by-row delete.

1 files changed, 71 insertions, 22 deletions

diff --git a/sql/sql_partition_admin.cc b/sql/sql_partition_admin.cc
index fee33303a04..98750314a4a 100644
--- a/sql/sql_partition_admin.cc
+++ b/sql/sql_partition_admin.cc
@@ -16,10 +16,10 @@
 #include "sql_parse.h"                      // check_one_table_access
 #include "sql_table.h"                      // mysql_alter_table, etc.
 #include "sql_lex.h"                        // Sql_statement
-#include "sql_truncate.h"                   // mysql_truncate_table,
-                                            // Truncate_statement
 #include "sql_admin.h"                      // Analyze/Check/.._table_statement
 #include "sql_partition_admin.h"            // Alter_table_*_partition
+#include "ha_partition.h"                   // ha_partition
+#include "sql_base.h"                       // open_and_lock_tables
 
 #ifndef WITH_PARTITION_STORAGE_ENGINE
 
@@ -46,7 +46,7 @@ bool Alter_table_analyze_partition_statement::execute(THD *thd)
   m_lex->alter_info.flags|= ALTER_ADMIN_PARTITION;
 
   res= Analyze_table_statement::execute(thd);
-    
+
   DBUG_RETURN(res);
 }
 
@@ -104,36 +104,85 @@ bool Alter_table_repair_partition_statement::execute(THD *thd)
 
 bool Alter_table_truncate_partition_statement::execute(THD *thd)
 {
+  int error;
+  ha_partition *partition;
+  ulong timeout= thd->variables.lock_wait_timeout;
   TABLE_LIST *first_table= thd->lex->select_lex.table_list.first;
-  bool res;
-  enum_sql_command original_sql_command;
   DBUG_ENTER("Alter_table_truncate_partition_statement::execute");
 
   /*
-    Execute TRUNCATE PARTITION just like TRUNCATE TABLE.
-    Some storage engines (InnoDB, partition) checks thd_sql_command,
-    so we set it to SQLCOM_TRUNCATE during the execution.
-  */
-  original_sql_command= m_lex->sql_command;
-  m_lex->sql_command= SQLCOM_TRUNCATE;
-  
-  /*
     Flag that it is an ALTER command which administrates partitions, used
     by ha_partition.
   */
-  m_lex->alter_info.flags|= ALTER_ADMIN_PARTITION;
-   
+  m_lex->alter_info.flags|= ALTER_ADMIN_PARTITION |
+                            ALTER_TRUNCATE_PARTITION;
+
+  /* Fix the lock types (not the same as ordinary ALTER TABLE). */
+  first_table->lock_type= TL_WRITE;
+  first_table->mdl_request.set_type(MDL_EXCLUSIVE);
+
   /*
-    Fix the lock types (not the same as ordinary ALTER TABLE).
+    Check table permissions and open it with a exclusive lock.
+    Ensure it is a partitioned table and finally, upcast the
+    handler and invoke the partition truncate method. Lastly,
+    write the statement to the binary log if necessary.
   */
-  first_table->lock_type= TL_WRITE;
-  first_table->mdl_request.set_type(MDL_SHARED_NO_READ_WRITE);
 
-  /* execute as a TRUNCATE TABLE */
-  res= Truncate_statement::execute(thd);
+  if (check_one_table_access(thd, DROP_ACL, first_table))
+    DBUG_RETURN(TRUE);
 
-  m_lex->sql_command= original_sql_command;
-  DBUG_RETURN(res);
+  if (open_and_lock_tables(thd, first_table, FALSE, 0))
+    DBUG_RETURN(TRUE);
+
+  /*
+    TODO: Add support for TRUNCATE PARTITION for NDB and other
+          engines supporting native partitioning.
+  */
+  if (first_table->table->s->db_type() != partition_hton)
+  {
+    my_error(ER_PARTITION_MGMT_ON_NONPARTITIONED, MYF(0));
+    DBUG_RETURN(TRUE);
+  }
+
+  /*
+    Under locked table modes this might still not be an exclusive
+    lock. Hence, upgrade the lock since the handler truncate method
+    mandates an exclusive metadata lock.
+  */
+  MDL_ticket *ticket= first_table->table->mdl_ticket;
+  if (thd->mdl_context.upgrade_shared_lock_to_exclusive(ticket, timeout))
+    DBUG_RETURN(TRUE);
+
+  tdc_remove_table(thd, TDC_RT_REMOVE_NOT_OWN, first_table->db,
+                   first_table->table_name, FALSE);
+
+  partition= (ha_partition *) first_table->table->file;
+
+  /* Invoke the handler method responsible for truncating the partition. */
+  if ((error= partition->truncate_partition(&thd->lex->alter_info)))
+    first_table->table->file->print_error(error, MYF(0));
+
+  /*
+    All effects of a truncate operation are committed even if the
+    operation fails. Thus, the query must be written to the binary
+    log. The only exception is a unimplemented truncate method. Also,
+    it is logged in statement format, regardless of the binlog format.
+  */
+  if (error != HA_ERR_WRONG_COMMAND)
+    error|= write_bin_log(thd, !error, thd->query(), thd->query_length());
+
+  /*
+    A locked table ticket was upgraded to a exclusive lock. After the
+    the query has been written to the binary log, downgrade the lock
+    to a shared one.
+  */
+  if (thd->locked_tables_mode)
+    ticket->downgrade_exclusive_lock(MDL_SHARED_NO_READ_WRITE);
+
+  if (! error)
+    my_ok(thd);
+
+  DBUG_RETURN(error);
 }
 
 #endif /* WITH_PARTITION_STORAGE_ENGINE */