Function CCH_fetch_page

src/jrd/cch.cpp:899–1068

}

void CCH_fetch_page(thread_db* tdbb, WIN* window, const bool read_shadow)
{
/**************************************
 *
 *	C C H _ f e t c h _ p a g e
 *
 **************************************
 *
 * Functional description
 *	Fetch a specific page.  If it's already in cache,
 *	so much the better.  When "compute_checksum" is 1, compute
 * 	the checksum of the page.  When it is 2, compute
 *	the checksum only when the page type is nonzero.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->getDatabase();
	BufferDesc* bdb = window->win_bdb;
	BufferControl* bcb = bdb->bdb_bcb;

	FbStatusVector* const status = tdbb->tdbb_status_vector;

	pag* page = bdb->bdb_buffer;
	bdb->bdb_incarnation = ++bcb->bcb_page_incarnation;

	tdbb->bumpStats(RuntimeStatistics::PAGE_READS);

	PageSpace* pageSpace = dbb->dbb_page_manager.findPageSpace(bdb->bdb_page.getPageSpaceID());
	fb_assert(pageSpace);

	jrd_file* file = pageSpace->file;
	const bool isTempPage = pageSpace->isTemporary();

	/*
	We will read a page, and if there is an I/O error we will try to
	use the shadow file, and try reading again, for a maximum of
	3 tries, before it gives up.

	The read_shadow flag is set to false only in the call to
	FETCH_NO_SHADOW, which is only called from validate
	code.

	read_shadow = false -> IF an I/O error occurs give up (exit
	the loop, clean up, and return). So the caller,
	validate in most cases, can know about it and attempt
	to remedy the situation.

	read_shadow = true -> IF an I/O error occurs attempt
	to rollover to the shadow file.  If the I/O error is
	persistant (more than 3 times) error out of the routine by
	calling CCH_unwind, and eventually punting out.
	*/

	class Pio : public CryptoManager::IOCallback
	{
	public:
		Pio(jrd_file* f, BufferDesc* b, bool tp, bool rs, PageSpace* ps)
			: file(f), bdb(b), isTempPage(tp),