firebird-mirror/src/jrd/tpc.cpp

/*
 *	PROGRAM:	JRD Access Method
 *	MODULE:		tpc.cpp
 *	DESCRIPTION:	TIP Cache for Database
 *
 * The contents of this file are subject to the Interbase Public
 * License Version 1.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy
 * of the License at http://www.Inprise.com/IPL.html
 *
 * Software distributed under the License is distributed on an
 * "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express
 * or implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code was created by Inprise Corporation
 * and its predecessors. Portions created by Inprise Corporation are
 * Copyright (C) Inprise Corporation.
 *
 * All Rights Reserved.
 * Contributor(s): ______________________________________.
 */

#include "firebird.h"
#include <string.h>
#include "../jrd/common.h"
#include "../jrd/jrd.h"
#include "../jrd/tpc.h"
#include "../jrd/ods.h"
#include "../jrd/tra.h"
#include "../jrd/lck.h"
#include "../jrd/pag.h"
#include "gen/iberror.h"
#include "../jrd/cch_proto.h"
#include "../jrd/err_proto.h"
#include "../jrd/gds_proto.h"
#include "../jrd/lck_proto.h"
#include "../jrd/mov_proto.h"
#include "../jrd/tpc_proto.h"
#include "../jrd/tra_proto.h"
#include "../common/classes/auto.h"
#include "../common/utils_proto.h"

using namespace Jrd;

static TxPageCache* allocate_tpc(thread_db*, SLONG);
static SLONG cache_transactions(thread_db*, TxPageCache**, SLONG);
static int extend_cache(thread_db*, SLONG);


int TPC_cache_state(thread_db* tdbb, SLONG number)
{
/**************************************
 *
 *	T P C _ c a c h e _ s t a t e
 *
 **************************************
 *
 * Functional description
 *	Get the current state of a transaction in the cache.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->getDatabase();
	CHECK_DBB(dbb);

	const TxPageCache* tip_cache = dbb->dbb_tip_cache;
	if (!tip_cache)
	{
		TPC_initialize_tpc(tdbb, number);
		tip_cache = dbb->dbb_tip_cache;
	}

	if (number && dbb->dbb_pc_transactions)
	{
		if (TRA_precommited(tdbb, number, number))
			return tra_precommitted;
	}

	// if the transaction is older than the oldest
	// transaction in our tip cache, it must be committed
	// hvlad: system transaction always committed too

	if (number < tip_cache->tpc_base || number == 0)
		return tra_committed;

	// locate the specific TIP cache block for the transaction

	const SLONG trans_per_tip = dbb->dbb_page_manager.transPerTIP;
	for (; tip_cache; tip_cache = tip_cache->tpc_next)
	{
		if ((ULONG) number < (ULONG) (tip_cache->tpc_base + trans_per_tip)) {
			return TRA_state(tip_cache->tpc_transactions, tip_cache->tpc_base, number);
		}
	}

	// Cover all possibilities by returning active

	return tra_active;
}


void TPC_initialize_tpc(thread_db* tdbb, SLONG number)
{
/**************************************
 *
 *	T P C _ i n i t i a l i z e _ t p c
 *
 **************************************
 *
 * Functional description
 *	At transaction startup, intialize the tip cache up to
 *	number.  This is used at TRA_start () time.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->getDatabase();
	CHECK_DBB(dbb);

	TxPageCache* tip_cache = dbb->dbb_tip_cache;
	if (!tip_cache)
	{
		cache_transactions(tdbb, NULL, 0);
		return;
	}

	// If there is already a cache, extend it if required.
	// find the end of the linked list, and cache
	// all transactions from that point up to the most recent transaction

	const SLONG trans_per_tip = dbb->dbb_page_manager.transPerTIP;

	TxPageCache** tip_cache_ptr;
	for (tip_cache_ptr = &dbb->dbb_tip_cache; *tip_cache_ptr;
		tip_cache_ptr = &(*tip_cache_ptr)->tpc_next)
	{
		tip_cache = *tip_cache_ptr;
	}

	if ((ULONG) number < (ULONG) (tip_cache->tpc_base + trans_per_tip))
		return;

	if (tip_cache->tpc_base < MAX_TRA_NUMBER - trans_per_tip)
		cache_transactions(tdbb, tip_cache_ptr, tip_cache->tpc_base + trans_per_tip);
}


void TPC_set_state(thread_db* tdbb, SLONG number, SSHORT state)
{
/**************************************
 *
 *	T P C _ s e t _ s t a t e
 *
 **************************************
 *
 * Functional description
 *	Set the state of a particular transaction
 *	in the TIP cache.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->getDatabase();
	CHECK_DBB(dbb);

	const SLONG trans_per_tip = dbb->dbb_page_manager.transPerTIP;
	const SLONG byte = TRANS_OFFSET(number % trans_per_tip);
	const SSHORT shift = TRANS_SHIFT(number);

	for (TxPageCache* tip_cache = dbb->dbb_tip_cache; tip_cache; tip_cache = tip_cache->tpc_next)
	{
		if ((ULONG) number < (ULONG) (tip_cache->tpc_base + trans_per_tip))
		{
			UCHAR* address = tip_cache->tpc_transactions + byte;
			*address &= ~(TRA_MASK << shift);
			*address |= state << shift;
			break;
		}
	}

	// right now we don't set the state of a transaction on a page
	// that has not already been cached -- this should probably be done
}


int TPC_snapshot_state(thread_db* tdbb, SLONG number)
{
/**************************************
 *
 *	T P C _ s n a p s h o t _ s t a t e
 *
 **************************************
 *
 * Functional description
 *	Get the current state of a transaction.
 *	Look at the TIP cache first, but if it
 *	is marked as still alive we must do some
 *	further checking to see if it really is.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->getDatabase();
	CHECK_DBB(dbb);

	const TxPageCache* tip_cache = dbb->dbb_tip_cache;
	if (!tip_cache)
	{
		cache_transactions(tdbb, NULL, 0);
		tip_cache = dbb->dbb_tip_cache;
	}

	if (number && dbb->dbb_pc_transactions)
	{
		if (TRA_precommited(tdbb, number, number)) {
			return tra_precommitted;
		}
	}

	// if the transaction is older than the oldest
	// transaction in our tip cache, it must be committed
	// hvlad: system transaction always committed too

	if (number < tip_cache->tpc_base || number == 0) {
		return tra_committed;
	}

	// locate the specific TIP cache block for the transaction

	const SLONG trans_per_tip = dbb->dbb_page_manager.transPerTIP;
	for (; tip_cache; tip_cache = tip_cache->tpc_next)
	{
		if ((ULONG) number < (ULONG) (tip_cache->tpc_base + trans_per_tip))
		{
			const USHORT state = TRA_state(tip_cache->tpc_transactions, tip_cache->tpc_base, number);

			// committed or dead transactions always stay that
			// way, so no need to check their current state

			if (state == tra_committed || state == tra_dead) {
				return state;
			}

			// see if we can get a lock on the transaction; if we can't
			// then we know it is still active
			Lock temp_lock;
			temp_lock.lck_dbb = dbb;
			temp_lock.lck_type = LCK_tra;
			temp_lock.lck_owner_handle = LCK_get_owner_handle(tdbb, temp_lock.lck_type);
			temp_lock.lck_parent = dbb->dbb_lock;
			temp_lock.lck_length = sizeof(SLONG);
			temp_lock.lck_key.lck_long = number;

			// If we can't get a lock on the transaction, it must be active.

			if (!LCK_lock(tdbb, &temp_lock, LCK_read, LCK_NO_WAIT))
			{
				fb_utils::init_status(tdbb->tdbb_status_vector);
				return tra_active;
			}

			fb_utils::init_status(tdbb->tdbb_status_vector);
			LCK_release(tdbb, &temp_lock);

			// as a last resort we must look at the TIP page to see
			// whether the transaction is committed or dead; to minimize
			// having to do this again we will check the state of all
			// other transactions on that page

			return TRA_fetch_state(tdbb, number);
		}
	}

	// if the transaction has been started since we last looked, extend the cache upward

	return extend_cache(tdbb, number);
}


void TPC_update_cache(thread_db* tdbb, const Ods::tx_inv_page* tip_page, SLONG sequence)
{
/**************************************
 *
 *	T P C _ u p d a t e _ c a c h e
 *
 **************************************
 *
 * Functional description
 *	A TIP page has been fetched into memory,
 *	so we should take the opportunity to update
 *	the TIP cache with the state of all transactions
 *	on that page.
 *
 **************************************/

	SET_TDBB(tdbb);
	Database* dbb = tdbb->getDatabase();
	CHECK_DBB(dbb);

	const SLONG trans_per_tip = dbb->dbb_page_manager.transPerTIP;
	const SLONG first_trans = sequence * trans_per_tip;

	// while we're in the area we can check to see if there are
	// any tip cache pages we can release--this is cheaper and
	// easier than finding out when a TIP page is dropped

	TxPageCache* tip_cache;
	while ( (tip_cache = dbb->dbb_tip_cache) )
	{
		if ((ULONG) dbb->dbb_oldest_transaction >= (ULONG) (tip_cache->tpc_base + trans_per_tip))
		{
			dbb->dbb_tip_cache = tip_cache->tpc_next;
			delete tip_cache;
		}
		else
			break;
	}

	// find the appropriate page in the TIP cache and assign all transaction
	// bits -- it's not worth figuring out which ones are actually used

	for (; tip_cache; tip_cache = tip_cache->tpc_next)
	{
		if (first_trans == tip_cache->tpc_base)
		{
			const USHORT l = TRANS_OFFSET(trans_per_tip);
			memcpy(tip_cache->tpc_transactions, tip_page->tip_transactions, l);
			break;
		}
	}

	// note that a potential optimization here would be to extend the cache
	// if the fetched page is not already in cache; it would involve a little
	// extra effort to make sure the pages remained in order, and since there
	// is a fetched page passed to us we can't fetch any other pages in this
	// routine, so I just decided not to do it - djb
}


static TxPageCache* allocate_tpc(thread_db* tdbb, SLONG base)
{
/**************************************
 *
 *	a l l o c a t e _ t p c
 *
 **************************************
 *
 * Functional description
 *	Create a tip cache block to hold the state
 *	of all transactions on one page.
 *
 **************************************/
	Database* dbb = tdbb->getDatabase();
	const SLONG trans_per_tip = dbb->dbb_page_manager.transPerTIP;

	// allocate a TIP cache block with enough room for all desired transactions

	TxPageCache* tip_cache = FB_NEW_RPT(*dbb->dbb_permanent, trans_per_tip / 4) TxPageCache();
	tip_cache->tpc_base = base;

	return tip_cache;
}


static SLONG cache_transactions(thread_db* tdbb, TxPageCache** tip_cache_ptr, SLONG oldest)
{
/**************************************
 *
 *	c a c h e _ t r a n s a c t i o n s
 *
 **************************************
 *
 * Functional description
 *	Cache the state of all the transactions since
 *	the last time this routine was called, or since
 *	the oldest interesting transaction.
 *
 **************************************/
	Database* dbb = tdbb->getDatabase();
	CHECK_DBB(dbb);

	// check the header page for the oldest and newest transaction numbers

#ifdef SUPERSERVER_V2
	const SLONG top = dbb->dbb_next_transaction;
	const ULONG hdr_oldest = dbb->dbb_oldest_transaction;
#else
	WIN window(HEADER_PAGE_NUMBER);
	const Ods::header_page* header = (Ods::header_page*) CCH_FETCH(tdbb, &window, LCK_read, pag_header);
	const SLONG top = header->hdr_next_transaction;
	const SLONG hdr_oldest = header->hdr_oldest_transaction;
	CCH_RELEASE(tdbb, &window);
#endif
	oldest = MAX(oldest, hdr_oldest);

	// allocate TxPageCache blocks to hold all transaction states --
	// assign one TxPageCache block per page to simplify cache maintenance

	const SLONG trans_per_tip = dbb->dbb_page_manager.transPerTIP;
	if (!tip_cache_ptr)
		tip_cache_ptr = &dbb->dbb_tip_cache;

	for (SLONG base = oldest - oldest % trans_per_tip; base <= top; base += trans_per_tip)
	{
		*tip_cache_ptr = allocate_tpc(tdbb, base);
		tip_cache_ptr = &(*tip_cache_ptr)->tpc_next;

		if (base >= MAX_TRA_NUMBER - trans_per_tip)
			break;
	}

	// now get the inventory of all transactions, which will
	// automatically fill in the tip cache pages

	TRA_get_inventory(tdbb, NULL, oldest, top);

	// hvlad: No need to cache TIP pages below hdr_oldest just refreshed from
	// header page. Moreover out tip cache can now contain an gap between last
	// cached tip page and new pages if our process was idle for long time

	for (TxPageCache* tip_cache = dbb->dbb_tip_cache;
		 tip_cache && ((ULONG) (tip_cache->tpc_base + trans_per_tip) < (ULONG) hdr_oldest);
		 tip_cache = dbb->dbb_tip_cache)
	{
		dbb->dbb_tip_cache = tip_cache->tpc_next;
		delete tip_cache;
	}

	return hdr_oldest;
}


static int extend_cache(thread_db* tdbb, SLONG number)
{
/**************************************
 *
 *	e x t e n d _ c a c h e
 *
 **************************************
 *
 * Functional description
 *	Extend the transaction inventory page
 *	cache to include at least all transactions
 *	up to the passed transaction, and return
 *	the state of the passed transaction.
 *
 **************************************/
	Database* dbb = tdbb->getDatabase();
	const SLONG trans_per_tip = dbb->dbb_page_manager.transPerTIP;

	// find the end of the linked list, and cache
	// all transactions from that point up to the
	// most recent transaction

	TxPageCache* tip_cache = 0;
	TxPageCache** tip_cache_ptr;
	for (tip_cache_ptr = &dbb->dbb_tip_cache; *tip_cache_ptr;
		tip_cache_ptr = &(*tip_cache_ptr)->tpc_next)
	{
		tip_cache = *tip_cache_ptr;
	}

	if (tip_cache->tpc_base < MAX_TRA_NUMBER - trans_per_tip)
	{
		const SLONG oldest = cache_transactions(tdbb, tip_cache_ptr, tip_cache->tpc_base + trans_per_tip);
		if (number < oldest)
			return tra_committed;
	}

	// find the right block for this transaction and return the state

	for (tip_cache = dbb->dbb_tip_cache; tip_cache; tip_cache = tip_cache->tpc_next)
	{
		if ((ULONG) number < (ULONG) (tip_cache->tpc_base + trans_per_tip))
			 return TRA_state(tip_cache->tpc_transactions, tip_cache->tpc_base, number);
	}

	// we should never get to this point, but if we do the
	// safest thing to do is return active

	return tra_active;
}