stephen barncard wrote:
> Remember a stack can both be a visible window with objects and
> a holder for scripts, it can also be a very efficient and
> addressable data container.
>
> The stack one compiles as an app can call other stacks that are not
> compiled. The best of both worlds.
Stack files are my favorite means of storage. These days I only use
text files for ultra-large repositories too big to be loaded into RAM
(with an index you'd be surprised how fast Rev can get in and out of
such things with seek). But for almost everything else I use stacks.
With stacks you can use custom props, which are by far the most
efficient means of using persistent arrays in Rev. RevTalk provides the
arrayEncode and arrayDecode functions which can be used for similar
purposes, but the overhead of translating arrays with those functions is
many times more costly than just opening a stack which has the data in
custom props.
I've tested with more than 100,000 custom props on stack files up to
100MB, and as long as you have the RAM it works great. Smaller files
(50MB or less) work amazingly fast in most memory configurations, even
with similarly large numbers of props.
Since custom props can be separated into property sets, you get two
levels of hierarchy supported with amazingly efficient access speed.
While it's possible to store arrays in props to extend that hierarchy
further, the speed is lost as those need to go through the internal
equivalent of arrayDecode to be accessed.
But as long as you stick with property sets and properties you get a
robust data store that's hard to beat for efficiency. If you need a
deeper hierarchy you can add objects there and use those props as well.
That's one of the other things I like about stack files as data
stores: you can store either text or binary data, or even native
objects, mixing and matching for nearly every need.
Extra bonus points: unlike a text file, with stacks you get an
automatic backup made during save, so if you have a power outage or
other interruption during save at least you'll have a copy of your last
saved file, found in the same directory with the same name preceded with
"~".
Tip: The engine currently doesn't prevent you from using property names
longer than 255 chars, but as noted in the Limits section of the docs
such names are not allowed. If you attempt to use a longer name it will
corrupt your stack file - see:
<http://quality.runrev.com/qacenter/show_bug.cgi?id=8840>
Just stick to the 255-char limit and you're good to go. Short strings
and of course numeric keys work great.
--
Richard Gaskin
Fourth World
Rev training and consulting: http://www.fourthworld.com
Webzine for Rev developers: http://www.revjournal.com
revJournal blog: http://revjournal.com/blog.irv
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