Bug#16218 - Crash on insert delayed

Bug#17294 - INSERT DELAYED puting an \n before data
Bug#16611 - INSERT DELAYED corrupts data
Bug#13707 - Server crash with INSERT DELAYED on MyISAM table
Combined as Bug#16218.

INSERT DELAYED crashed in 5.0 on a table with a varchar that 
could be NULL and was created pre-5.0 (Bugs 16218 and 13707).
INSERT DELAYED corrupted data in 5.0 on a table with varchar 
fields that was created pre-5.0 (Bugs 17294 and 16611).

In case of INSERT DELAYED the open table is copied from the
delayed insert thread to be able to create a record for the 
queue. When copying the fields, a method was used that did 
convert old varchar to new varchar fields and did not set up 
some pointers into the record buffer of the table.

The field conversion was guilty for the misinterpretation of 
the record contents by the delayed insert thread. The wrong
pointer setup was guilty for the crashes.

For Bug 13707 (Server crash with INSERT DELAYED on MyISAM table)
I fixed the above mentioned method to set up one of the pointers.
For Bug 16218 I set up the other pointers too.

But when looking at the corruptions I got aware that converting
the field type was totally wrong for INSERT DELAYED. The copied
table is used to create a record that is to be sent to the
delayed insert thread. Of course it can interpret the record
correctly only if all field types are the same in both table
objects.

So I revoked the fix for Bug 13707 and changed the new_field() 
method so that it can suppress conversions.

No test case as this is a migration problem. One needs to
create a table with 4.x and use it with 5.x. I added two
test scripts to the bug report.

sql/field.cc

@@ -1515,7 +1515,8 @@ bool Field::optimize_range(uint idx, uint part)
 }
 
 
-Field *Field::new_field(MEM_ROOT *root, struct st_table *new_table)
+Field *Field::new_field(MEM_ROOT *root, struct st_table *new_table,
+                        bool keep_type __attribute__((unused)))
 {
   Field *tmp;
   if (!(tmp= (Field*) memdup_root(root,(char*) this,size_of())))
@@ -1540,7 +1541,7 @@ Field *Field::new_key_field(MEM_ROOT *root, struct st_table *new_table,
                             uint new_null_bit)
 {
   Field *tmp;
-  if ((tmp= new_field(root, new_table)))
+  if ((tmp= new_field(root, new_table, table == new_table)))
   {
     tmp->ptr=      new_ptr;
     tmp->null_ptr= new_null_ptr;
@@ -6224,29 +6225,21 @@ uint Field_string::max_packed_col_length(uint max_length)
 }
 
 
-Field *Field_string::new_field(MEM_ROOT *root, struct st_table *new_table)
+Field *Field_string::new_field(MEM_ROOT *root, struct st_table *new_table,
+                               bool keep_type)
 {
   Field *new_field;
 
-  if (type() != MYSQL_TYPE_VAR_STRING || table == new_table)
-    return Field::new_field(root, new_table);
+  if (type() != MYSQL_TYPE_VAR_STRING || keep_type)
+    return Field::new_field(root, new_table, keep_type);
 
   /*
     Old VARCHAR field which should be modified to a VARCHAR on copy
     This is done to ensure that ALTER TABLE will convert old VARCHAR fields
     to now VARCHAR fields.
   */
-  if ((new_field= new Field_varstring(field_length, maybe_null(),
-                                      field_name, new_table, charset())))
-  {
-    /*
-      delayed_insert::get_local_table() needs a ptr copied from old table.
-      This is what other new_field() methods do too. The above method of
-      Field_varstring sets ptr to NULL.
-    */
-    new_field->ptr= ptr;
-  }
-  return new_field;
+  return new Field_varstring(field_length, maybe_null(),
+                             field_name, new_table, charset());
 }
 
 /****************************************************************************
@@ -6738,9 +6731,11 @@ int Field_varstring::cmp_binary(const char *a_ptr, const char *b_ptr,
 }
 
 
-Field *Field_varstring::new_field(MEM_ROOT *root, struct st_table *new_table)
+Field *Field_varstring::new_field(MEM_ROOT *root, struct st_table *new_table,
+                                  bool keep_type)
 {
-  Field_varstring *res= (Field_varstring*) Field::new_field(root, new_table);
+  Field_varstring *res= (Field_varstring*) Field::new_field(root, new_table,
+                                                            keep_type);
   if (res)
     res->length_bytes= length_bytes;
   return res;

sql/field.h

@@ -211,7 +211,8 @@ public:
   */
   virtual bool can_be_compared_as_longlong() const { return FALSE; }
   virtual void free() {}
-  virtual Field *new_field(MEM_ROOT *root, struct st_table *new_table);
+  virtual Field *new_field(MEM_ROOT *root, struct st_table *new_table,
+                           bool keep_type);
   virtual Field *new_key_field(MEM_ROOT *root, struct st_table *new_table,
                                char *new_ptr, uchar *new_null_ptr,
                                uint new_null_bit);
@@ -1033,7 +1034,7 @@ public:
   enum_field_types real_type() const { return FIELD_TYPE_STRING; }
   bool has_charset(void) const
   { return charset() == &my_charset_bin ? FALSE : TRUE; }
-  Field *new_field(MEM_ROOT *root, struct st_table *new_table);
+  Field *new_field(MEM_ROOT *root, struct st_table *new_table, bool keep_type);
 };
 
 
@@ -1105,7 +1106,7 @@ public:
   enum_field_types real_type() const { return MYSQL_TYPE_VARCHAR; }
   bool has_charset(void) const
   { return charset() == &my_charset_bin ? FALSE : TRUE; }
-  Field *new_field(MEM_ROOT *root, struct st_table *new_table);
+  Field *new_field(MEM_ROOT *root, struct st_table *new_table, bool keep_type);
   Field *new_key_field(MEM_ROOT *root, struct st_table *new_table,
                        char *new_ptr, uchar *new_null_ptr,
                        uint new_null_bit);

sql/sql_insert.cc

@@ -17,6 +17,44 @@
 
 /* Insert of records */
 
+/*
+  INSERT DELAYED
+
+  Insert delayed is distinguished from a normal insert by lock_type ==
+  TL_WRITE_DELAYED instead of TL_WRITE. It first tries to open a
+  "delayed" table (delayed_get_table()), but falls back to
+  open_and_lock_tables() on error and proceeds as normal insert then.
+
+  Opening a "delayed" table means to find a delayed insert thread that
+  has the table open already. If this fails, a new thread is created and
+  waited for to open and lock the table.
+
+  If accessing the thread succeeded, in
+  delayed_insert::get_local_table() the table of the thread is copied
+  for local use. A copy is required because the normal insert logic
+  works on a target table, but the other threads table object must not
+  be used. The insert logic uses the record buffer to create a record.
+  And the delayed insert thread uses the record buffer to pass the
+  record to the table handler. So there must be different objects. Also
+  the copied table is not included in the lock, so that the statement
+  can proceed even if the real table cannot be accessed at this moment.
+
+  Copying a table object is not a trivial operation. Besides the TABLE
+  object there are the field pointer array, the field objects and the
+  record buffer. After copying the field objects, their pointers into
+  the record must be "moved" to point to the new record buffer.
+
+  After this setup the normal insert logic is used. Only that for
+  delayed inserts write_delayed() is called instead of write_record().
+  It inserts the rows into a queue and signals the delayed insert thread
+  instead of writing directly to the table.
+
+  The delayed insert thread awakes from the signal. It locks the table,
+  inserts the rows from the queue, unlocks the table, and waits for the
+  next signal. It does normally live until a FLUSH TABLES or SHUTDOWN.
+
+*/
+
 #include "mysql_priv.h"
 #include "sp_head.h"
 #include "sql_trigger.h"
@@ -1466,6 +1504,7 @@ TABLE *delayed_insert::get_local_table(THD* client_thd)
   my_ptrdiff_t adjust_ptrs;
   Field **field,**org_field, *found_next_number_field;
   TABLE *copy;
+  DBUG_ENTER("delayed_insert::get_local_table");
 
   /* First request insert thread to get a lock */
   status=1;
@@ -1489,31 +1528,47 @@ TABLE *delayed_insert::get_local_table(THD* client_thd)
     }
   }
 
+  /*
+    Allocate memory for the TABLE object, the field pointers array, and
+    one record buffer of reclength size. Normally a table has three
+    record buffers of rec_buff_length size, which includes alignment
+    bytes. Since the table copy is used for creating one record only,
+    the other record buffers and alignment are unnecessary.
+  */
   client_thd->proc_info="allocating local table";
   copy= (TABLE*) client_thd->alloc(sizeof(*copy)+
 				   (table->s->fields+1)*sizeof(Field**)+
 				   table->s->reclength);
   if (!copy)
     goto error;
+
+  /* Copy the TABLE object. */
   *copy= *table;
   copy->s= &copy->share_not_to_be_used;
   // No name hashing
   bzero((char*) &copy->s->name_hash,sizeof(copy->s->name_hash));
   /* We don't need to change the file handler here */
 
-  field=copy->field=(Field**) (copy+1);
-  copy->record[0]=(byte*) (field+table->s->fields+1);
-  memcpy((char*) copy->record[0],(char*) table->record[0],table->s->reclength);
+  /* Assign the pointers for the field pointers array and the record. */
+  field= copy->field= (Field**) (copy + 1);
+  copy->record[0]= (byte*) (field + table->s->fields + 1);
+  memcpy((char*) copy->record[0], (char*) table->record[0],
+         table->s->reclength);
 
-  /* Make a copy of all fields */
-
-  adjust_ptrs=PTR_BYTE_DIFF(copy->record[0],table->record[0]);
+  /*
+    Make a copy of all fields.
+    The copied fields need to point into the copied record. This is done
+    by copying the field objects with their old pointer values and then
+    "move" the pointers by the distance between the original and copied
+    records. That way we preserve the relative positions in the records.
+  */
+  adjust_ptrs= PTR_BYTE_DIFF(copy->record[0], table->record[0]);
 
-  found_next_number_field=table->found_next_number_field;
-  for (org_field=table->field ; *org_field ; org_field++,field++)
+  found_next_number_field= table->found_next_number_field;
+  for (org_field= table->field; *org_field; org_field++, field++)
   {
-    if (!(*field= (*org_field)->new_field(client_thd->mem_root,copy)))
-      return 0;
+    if (!(*field= (*org_field)->new_field(client_thd->mem_root, copy, 1)))
+      DBUG_RETURN(0);
     (*field)->orig_table= copy;			// Remove connection
     (*field)->move_field(adjust_ptrs);		// Point at copy->record[0]
     if (*org_field == found_next_number_field)
@@ -1540,14 +1595,14 @@ TABLE *delayed_insert::get_local_table(THD* client_thd)
   /* Adjust lock_count. This table object is not part of a lock. */
   copy->lock_count= 0;
 
-  return copy;
+  DBUG_RETURN(copy);
 
   /* Got fatal error */
  error:
   tables_in_use--;
   status=1;
   pthread_cond_signal(&cond);			// Inform thread about abort
-  return 0;
+  DBUG_RETURN(0);
 }
 
 

sql/sql_select.cc

@@ -8217,7 +8217,8 @@ Field* create_tmp_field_from_field(THD *thd, Field* org_field,
                                    org_field->field_name, table,
                                    org_field->charset());
   else
-    new_field= org_field->new_field(thd->mem_root, table);
+    new_field= org_field->new_field(thd->mem_root, table,
+                                    table == org_field->table);
   if (new_field)
   {
     if (item)
@@ -13072,7 +13073,7 @@ setup_copy_fields(THD *thd, TMP_TABLE_PARAM *param,
 	   saved value
 	*/
 	Field *field= item->field;
-	item->result_field=field->new_field(thd->mem_root,field->table);
+	item->result_field=field->new_field(thd->mem_root,field->table, 1);
 	char *tmp=(char*) sql_alloc(field->pack_length()+1);
 	if (!tmp)
 	  goto err;

sql/sql_trigger.cc

@@ -736,7 +736,8 @@ bool Table_triggers_list::prepare_record1_accessors(TABLE *table)
       QQ: it is supposed that it is ok to use this function for field
       cloning...
     */
-    if (!(*old_fld= (*fld)->new_field(&table->mem_root, table)))
+    if (!(*old_fld= (*fld)->new_field(&table->mem_root, table,
+                                      table == (*fld)->table)))
       return 1;
     (*old_fld)->move_field((my_ptrdiff_t)(table->record[1] -
                                           table->record[0]));

sql/table.cc

@@ -802,7 +802,8 @@ int openfrm(THD *thd, const char *name, const char *alias, uint db_stat,
 	    if (!(field->flags & BLOB_FLAG))
 	    {					// Create a new field
 	      field=key_part->field=field->new_field(&outparam->mem_root,
-						     outparam);
+                                                     outparam,
+                                                     outparam == field->table);
 	      field->field_length=key_part->length;
 	    }
 	  }