USP_FAFEVENTDATACACHE_GET

create procedure dbo.USP_FAFEVENTDATACACHE_GET
(
    @DATA xml = null output,
    @EVENTID uniqueidentifier,
    @CACHEKEY nvarchar(512)
)
as
begin
    declare @EXPIRATIONDATE as datetime;
    declare @ISCALCULATING as bit;
    declare @NOW as datetime;

    set @NOW = GETDATE();

    select
        @DATA = DATA,
        @EXPIRATIONDATE = EXPIRATIONDATE,
        @ISCALCULATING = ISCALCULATING
    from dbo.FAFEVENTDATACACHE
    where EVENTID = @EVENTID and CACHEKEY = @CACHEKEY

    if @DATA is not null    -- cache exists

    begin
        if @NOW > @EXPIRATIONDATE    -- expired

        begin
            if @ISCALCULATING = 0    -- no re-calculating thread running

            begin
                set @DATA = null;    -- return no data so the caller has to calculate by itself

            end
        end
    end
end