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/* Copyright (C) 2005 MySQL AB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#ifndef TABLE_MAPPING_H
#define TABLE_MAPPING_H
/* Forward declarations */
#ifndef MYSQL_CLIENT
struct TABLE;
#else
class Table_map_log_event;
typedef Table_map_log_event TABLE;
void free_table_map_log_event(TABLE *table);
#endif
/*
CLASS table_mapping
RESPONSIBILITIES
The table mapping is used to map table id's to table pointers
COLLABORATION
RELAY_LOG For mapping table id:s to tables when receiving events.
*/
/*
Guilhem to Mats:
in the table_mapping class, the memory is allocated and never freed (until
destruction). So this is a good candidate for allocating inside a MEM_ROOT:
it gives the efficient allocation in chunks (like in expand()). So I have
introduced a MEM_ROOT.
Note that inheriting from Sql_alloc had no effect: it has effects only when
"ptr= new table_mapping" is called, and this is never called. And it would
then allocate from thd->mem_root which is a highly volatile object (reset
from example after executing each query, see dispatch_command(), it has a
free_root() at end); as the table_mapping object is supposed to live longer
than a query, it was dangerous.
A dedicated MEM_ROOT needs to be used, see below.
*/
class table_mapping {
private:
MEM_ROOT m_mem_root;
public:
enum enum_error {
ERR_NO_ERROR = 0,
ERR_LIMIT_EXCEEDED,
ERR_MEMORY_ALLOCATION
};
table_mapping();
~table_mapping();
TABLE* get_table(ulong table_id);
int set_table(ulong table_id, TABLE* table);
int remove_table(ulong table_id);
void clear_tables();
ulong count() const { return m_table_ids.records; }
private:
/*
This is a POD (Plain Old Data). Keep it that way (we apply offsetof() to
it, which only works for PODs)
*/
struct entry {
ulong table_id;
union {
TABLE *table;
entry *next;
};
};
entry *find_entry(ulong table_id)
{
return (entry *) my_hash_search(&m_table_ids,
(uchar*)&table_id,
sizeof(table_id));
}
int expand();
/*
Head of the list of free entries; "free" in the sense that it's an
allocated entry free for use, NOT in the sense that it's freed
memory.
*/
entry *m_free;
/* Correspondance between an id (a number) and a TABLE object */
HASH m_table_ids;
};
#endif
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