maria-discuss team mailing list archive

[Justin Swanhart <greenlion@xxxxxxxxx>]

Hi Sergei!

I moved this back to the mailing list, because of your .FRM explanation,
and also because I'd like to explain rasters.  A GIS raster is an array of
data represented as a raster image.  Rasters have "layers" and each layer
can have a different measurement in it.  It is most commonly used for
height maps.

The pgsql schema that I sent you is for a personal project of mine that
uses Voxel.js (http://voxeljs.com/) to turn real world height maps from the
space shuttle (SRTM v3 data) into interpolated 1 meter resolution voxel
(minecraft-like, as 1 block = 1 sq meter) landscapes.  I intersect the
raster data with the GIS data from OSM (open street map) so that I can
render buildings, roads, forest areas, rivers, etc, somewhat correctly
(overpasses, underhangs, and missing building heights cause significant
problems.).

The ST_PixelsAsCentroids or ST_PixelsAsPoints can be used to get the
specific value for a band in the raster, such as the height in a specific
30sq meter area (for the 1 arcsecond resolution of the SRTM data).

I could never do such a thing in MySQL, and that makes me sad :(


On Wed, Oct 12, 2016 at 9:34 AM, Sergei Golubchik <serg@xxxxxxxxxxx> wrote:

> Hi, Justin!
>
> On Oct 12, Justin Swanhart wrote:
> >
> > Regarding SET PERSIST, yes, it has dangers.  One of them would be to
> > set the buffer pool too large, so I filed a MySQL FR to set the BP to
> > the default size if the malloc fails.  It can be increased dynamically
> > later.  But there are many changes that could cause problems.  This
> > feature has to be managed carefully.  Then again, Oracle RDBMS has had
> > pfile configuration for well over a decade, and it is functionally
> > equivalent to a binary my.cnf in the data dir.
>
> Right. Personally I fully expect that we will need to suport SET PERSIST
> eventually. It's just so convenient. I only said it needs some very
> careful thinking - and I was responsible for security@xxxxxxxxx for ten
> years and now for security@xxxxxxxxxxx for six, so I am a bit paranoid
> about this :)
>
> > re: GIS, well, gdal and proj are  used by almost every application
> > that deals with GIS. What does the extra accuracy get you?  Anyway,
> > rasters really aren't useful without table functions, as you can't get
> > the data from each point without them.
>
> I don't really know what rasters are.
>
> And I do not actually *use* GIS, so may be extra accuracy is not useful.
> I'd think it might be particularly important for functions like
> ST_TOUCHES().
>
> I really want MariaDB to have table functions - perhaps we will have
> them in 10.3.
>
> > Some more questions:
> > Even though .FRM are optional, that still doesn't necessarily make DDL
> > changes atomic, does it?
>
> If the engine declares FRM optional, then the whole DDL is happening
> inside the engine, and it's up to the engine to make it atomic. I
> expect that when we'll make FRMs optional for InnoDB, InnoDB DDLs
> will be atomic.
>
> Regards,
> Sergei
> Chief Architect MariaDB
> and security@xxxxxxxxxxx
>