[mapguide-internals] Avoiding unnecessary Tile Cache invalidation (Trac Ticket 1332)

[Jason Birch]

My suggestion has always been to treat tile sets as separate resources
and allow them to be included in multiple map definitions. This
increases usefulness and stability all in one go.

On 2010-04-27, Jackie Ng <jumpinjackie at gmail.com> wrote:
>
> Hi All,
>
> At Zac's suggestion, I'm spawning this thread off of discussions on Trac
> #1332 (http://trac.osgeo.org/mapguide/ticket/1332) to stimulate some more
> discussion on this list.
>
> Sometime last week, I heard a tale of total frustration about how a Tile
> Cache of 1.5 million tiles that was built over 1.5-2 days was instantly
> trashed the moment a dynamic untiled layer was added to the map definition
> and saved back into the repository.
>
> That got me thinking about whether something as innocuous as changing the
> description or background color of a map definition w/ tiled layers would
> invalidate the tile cache so I tested this out and just as I feared, it
> indeed wiped out the tile cache.
>
> My initial thoughts were that tiling's only concerned with the base layer
> settings in the Map Definition. So theoretically speaking, doing
> modifications that don't affect the base layers should not affect the
> integrity of the original tiles.
>
> Now according to Tom, there is a whole stack of dependencies that would have
> to be checked such as Feature Source changes, Symbol changes, Layer
> Definition changes in order to determine whether a Map Definition's Tile
> Cache needs to be rebuilt. I wonder what overhead would be incurred by
> performing these checks (if it hasn't been done already).
>
> There's also renaming the tile cache directory before saving (also suggested
> by Tom) and then renaming back. I wonder what other things can be done so
> that the Tile Cache is cleared *only* if it has to be.
>
> - Jackie
> --
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> Sent from the MapGuide Internals mailing list archive at Nabble.com.
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