Function CCH_fake

src/jrd/cch.cpp:679–771

pag* CCH_fake(thread_db* tdbb, WIN* window, int wait)
{
/**************************************
 *
 *	C C H _ f a k e
 *
 **************************************
 *
 * Functional description
 *	Fake a fetch to a page.  Rather than reading it, however,
 *	zero it in memory.  This is used when allocating a new page.
 *
 * input
 *	wait:	1 => Wait as long as necessary to get the latch.
 *				This can cause deadlocks of course.
 *			0 => If the latch can't be acquired immediately,
 *				or an IO would be necessary, then give
 *				up and return 0.
 *			<negative number> => Latch timeout interval in seconds.
 *
 * return
 *	pag pointer if successful.
 *	NULL pointer if timeout occurred (only possible if wait <> 1).
 *	NULL pointer if wait=0 and the faked page would have to be
 *			before reuse.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* const dbb = tdbb->getDatabase();
	BufferControl *bcb = dbb->dbb_bcb;

	CCH_TRACE(("FAKE    %d:%06d", window->win_page.getPageSpaceID(), window->win_page.getPageNum()));

	// if there has been a shadow added recently, go out and
	// find it before we grant any more write locks

	if (dbb->dbb_ast_flags & DBB_get_shadows)
		SDW_get_shadows(tdbb);

	BufferDesc* bdb = get_buffer(tdbb, window->win_page, SYNC_EXCLUSIVE, wait);
	if (!bdb)
		return NULL;			// latch timeout occurred

	fb_assert(bdb->bdb_page == window->win_page);

	// If a dirty orphaned page is being reused - better write it first
	// to clear current precedences and checkpoint state. This would also
	// update the bcb_free_pages field appropriately.

	if (bdb->bdb_flags & (BDB_dirty | BDB_db_dirty))
	{
		// If the caller didn't want to wait at all, then
		// return 'try to fake an other page' to the caller.

		if (!wait)
		{
			bdb->release(tdbb, true);
			return NULL;