[postgis-users] postgis geometry sizes

[Paul Ramsey]

The 0.X geometries have a lot of overhead in them by their nature.   
They store 3 ordinates even if you have 2D data.  They have a pretty  
big header, which can be a large proportion of object size for small  
geometries (like points, or 2-vertex linestrings).  As a result,  
seeing a 100% fluff-up in data volume is not unexpected.  For points  
and small linestrings, 200% would be unsurprising.  Plus, for simple  
geometries, the spatial indexes themselves can be quite large, as the  
bbox of a two-vertex linestring has as many ordinates as the original  
shape (though a much smaller structure size due to a smaller  
header).  As a previous poster noted, if you have been doing  
processing on the data in the table itself, you probably have a large  
number of dead tuples.  VACUUM FULL your table, then cluster it on an  
index to reduce it to the minimum possible on-disk size.  To reduce  
your size even more, upgrade to the 1.X series, which have a much  
less fluffy data structures (no unnecessary 3D overhead, smaller  
headers, reduced precision indexes).

P

On 5-Mar-06, at 2:20 PM, Eric Lam wrote:

> I am using postgresql 7.4.5 and Postgis 0.8.2. The select  
> postgis_full_version() did not work for me. But I know these were  
> the versions built from source.
>
> On 3/6/06, Paul Ramsey <pramsey at refractions.net> wrote: What  
> PostGIS version are you running ( select postgis_full_version() )?
>
> On 4-Mar-06, at 11:43 PM, Eric Lam wrote:
>
> > Hi List,
> >
> > I have a set of data [multilinestrings]. The data is about 2gig. I
> > have processed the data and the data is now 11gig on disc, using
> > the realtion_size() command. I have counted the number of points
> > and the 11gig data set has 1/4 the number of points as the 2gig
> > data set. Does anyone know why this is? I am running short on disc
> > space.
> >
> > Thanks
> >
> > Eric Lam
> > _______________________________________________
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