Function CCH_release

src/jrd/cch.cpp:2020–2149

void CCH_release(thread_db* tdbb, WIN* window, const bool release_tail)
{
/**************************************
 *
 *	C C H _ r e l e a s e
 *
 **************************************
 *
 * Functional description
 *	Release a window. If the release_tail
 *	flag is true then make the buffer
 *	least-recently-used.
 *
 **************************************/
	SET_TDBB(tdbb);

	BufferDesc* const bdb = window->win_bdb;
	BLKCHK(bdb, type_bdb);

	BufferControl* bcb = bdb->bdb_bcb;

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

	// A large sequential scan has requested that the garbage
	// collector garbage collect. Mark the buffer so that the
	// page isn't released to the LRU tail before the garbage
	// collector can process the page.

	if (window->win_flags & WIN_large_scan && window->win_flags & WIN_garbage_collect)
	{
		bdb->bdb_flags |= BDB_garbage_collect;
		window->win_flags &= ~WIN_garbage_collect;
	}

	const bool mustWrite = (bdb->bdb_flags & BDB_must_write) ||
		bcb->bcb_database->dbb_backup_manager->databaseFlushInProgress();

	if (bdb->bdb_writers == 1 || bdb->bdb_use_count == 1 ||
		(bdb->bdb_writers == 0 && mustWrite))
	{
		const bool marked = bdb->bdb_flags & BDB_marked;
		bdb->bdb_flags &= ~(BDB_writer | BDB_marked | BDB_faked);

		if (marked)
			bdb->unLockIO(tdbb);

		if (mustWrite)
		{
			// Downgrade exclusive latch to shared to allow concurrent share access
			// to page during I/O.

			bdb->downgrade(SYNC_SHARED);

			if (!write_buffer(tdbb, bdb, bdb->bdb_page, false, tdbb->tdbb_status_vector, true))
			{
				insertDirty(bcb, bdb);
				CCH_unwind(tdbb, true);
			}