Function clear_precedence

src/jrd/cch.cpp:3325–3366

static void clear_precedence(thread_db* tdbb, BufferDesc* bdb)
{
/**************************************
 *
 *	c l e a r _ p r e c e d e n c e
 *
 **************************************
 *
 * Functional description
 *	Clear precedence relationships to lower precedence block.
 *
 **************************************/
	SET_TDBB(tdbb);

	if (QUE_EMPTY(bdb->bdb_lower))
		return;

	BufferControl* const bcb = bdb->bdb_bcb;
	Sync precSync(&bcb->bcb_syncPrecedence, "clear_precedence");
	if (!bcb->bcb_syncPrecedence.ourExclusiveLock())
		precSync.lock(SYNC_EXCLUSIVE);

	// Loop thru lower precedence buffers.  If any can be downgraded,
	// by all means down grade them.

	while (QUE_NOT_EMPTY(bdb->bdb_lower))
	{
		QUE que_inst = bdb->bdb_lower.que_forward;
		Precedence* precedence = BLOCK(que_inst, Precedence, pre_lower);
		BufferDesc* low_bdb = precedence->pre_low;
		QUE_DELETE(precedence->pre_higher);
		QUE_DELETE(precedence->pre_lower);

		precedence->pre_hi = (BufferDesc*) bcb->bcb_free;
		bcb->bcb_free = precedence;
		if (!(precedence->pre_flags & PRE_cleared))
		{
			if (low_bdb->bdb_ast_flags & BDB_blocking)
				PAGE_LOCK_RE_POST(tdbb, bcb, low_bdb->bdb_lock);
		}
	}
}


static void down_grade(thread_db* tdbb, BufferDesc* bdb, int high)