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/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
* vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
*
* Copyright (C) 2008 Sun Microsystems
*
* 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef DRIZZLED_HA_TRX_INFO_H
#define DRIZZLED_HA_TRX_INFO_H
/**
Either statement transaction or normal transaction - related
thread-specific storage engine data.
If a storage engine participates in a statement/transaction,
an instance of this class is present in
session->transaction.{stmt|all}.ha_list. The addition to
{stmt|all}.ha_list is made by trans_register_ha().
When it's time to commit or rollback, each element of ha_list
is used to access storage engine's prepare()/commit()/rollback()
methods, and also to evaluate if a full two phase commit is
necessary.
@sa General description of transaction handling in handler.cc.
*/
class Ha_trx_info
{
public:
/** Register this storage engine in the given transaction context. */
void register_ha(Session_TRANS *trans, handlerton *ht_arg)
{
assert(m_flags == 0);
assert(m_ht == NULL);
assert(m_next == NULL);
m_ht= ht_arg;
m_flags= (int) TRX_READ_ONLY; /* Assume read-only at start. */
m_next= trans->ha_list;
trans->ha_list= this;
}
/** Clear, prepare for reuse. */
void reset()
{
m_next= NULL;
m_ht= NULL;
m_flags= 0;
}
Ha_trx_info() { reset(); }
void set_trx_read_write()
{
assert(is_started());
m_flags|= (int) TRX_READ_WRITE;
}
bool is_trx_read_write() const
{
assert(is_started());
return m_flags & (int) TRX_READ_WRITE;
}
bool is_started() const { return m_ht != NULL; }
/** Mark this transaction read-write if the argument is read-write. */
void coalesce_trx_with(const Ha_trx_info *stmt_trx)
{
/*
Must be called only after the transaction has been started.
Can be called many times, e.g. when we have many
read-write statements in a transaction.
*/
assert(is_started());
if (stmt_trx->is_trx_read_write())
set_trx_read_write();
}
Ha_trx_info *next() const
{
assert(is_started());
return m_next;
}
handlerton *ht() const
{
assert(is_started());
return m_ht;
}
private:
enum { TRX_READ_ONLY= 0, TRX_READ_WRITE= 1 };
/** Auxiliary, used for ha_list management */
Ha_trx_info *m_next;
/**
Although a given Ha_trx_info instance is currently always used
for the same storage engine, 'ht' is not-NULL only when the
corresponding storage is a part of a transaction.
*/
handlerton *m_ht;
/**
Transaction flags related to this engine.
Not-null only if this instance is a part of transaction.
May assume a combination of enum values above.
*/
unsigned char m_flags;
};
#endif /* DRIZZLED_HA_TRX_INFO_H */
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