Function TRA_setup_request_snapshot

src/jrd/tra.cpp:146–179

}

void TRA_setup_request_snapshot(Jrd::thread_db* tdbb, Jrd::Request* request)
{
	// This function is called whenever request is started in a transaction.
	// Setup context to preserve read consistency in READ COMMITTED transactions.

	Jrd::jrd_tra* transaction = request->req_transaction;

	// We assume that request is already attached to a transaction
	fb_assert(transaction);

	// If we are not READ COMMITTED or read consistency is not needed then nothing to do here
	if (!(transaction->tra_flags & TRA_read_committed) || !(transaction->tra_flags & TRA_read_consistency))
		return;

	// See if there is any request right above us in the call stack
	Request* org_request = TRA_get_prior_request(tdbb);

	if (org_request && org_request->req_transaction == transaction)
	{
		fb_assert(org_request->req_snapshot.m_owner);
		request->req_snapshot.m_owner = org_request->req_snapshot.m_owner;
		return;
	}

	// If we are a top-level request or caller is executed in a different transaction,
	// we need to set up statement snapshot for read consistency and own it

	request->req_snapshot.m_owner = request;
	request->req_snapshot.m_number = 0;

	request->req_snapshot.m_handle =
		tdbb->getDatabase()->dbb_tip_cache->beginSnapshot(tdbb,
			tdbb->getAttachment()->att_attachment_id, request->req_snapshot.m_number);
}


void TRA_release_request_snapshot(Jrd::thread_db* tdbb, Jrd::Request* request)