[postgis-devel] Re: [postgis-users] Memory leak in translate function in RC3

[strk at refractions.net]

Please let's move this discussion on postgis-devel.

I've found a solution and what seems to be a postgresql bug.

Our transform() function is a plpgsql wrapper to transform_geometry()
which is a C function.

The C function (transform_geometry) takes 4 args:
	geometry
	input_proj4_text
	output_proj4_text
	output_srid

The wrapper extracts *_proj4_text invoking another "internal" function:
get_proj4_from_srid(). This is an 'sql' function:

  CREATE OR REPLACE FUNCTION get_proj4_from_srid(integer) RETURNS text AS
     'SELECT proj4text::text FROM spatial_ref_sys WHERE srid= $1'
     LANGUAGE 'sql' IMMUTABLE STRICT; 

If I replace:
	 transform(setSRID(geom, X), Y)

with:

	transform_geometry(geom, get_proj4_from_srid(X),
		get_proj4_from_srid(Y), Y)

The size keeps growing as before. Buf if I replace get_proj4_from_srid()
calls with their output memory keeps low:

	transform_geometry(geom, X_PROJ4_TEXT, Y_PROJ4_TEXT, Y)

Bryce, can you confirm this ?

--strk;

	
On Wed, Mar 16, 2005 at 12:28:12PM +0100, strk at refractions.net wrote:
> Bryce, I've gone through the code and enforced some other early memory
> release. I can't see any real leak though...
> 
> Can you send the output of explain analyze for the query ?
> 
> Also, 268435456 is a BIG number for a single alloc...
> maybe it's the postgres buffer growing ?
> 
> Can you also check sum(mem_size(shape)) from crs_feature_name; ?
> 
> --strk;
> 
> On Wed, Mar 16, 2005 at 05:42:54PM +1300, Bryce Watkins wrote:
> > Hi strk,
> >  
> > I have defiantly found a leak this time :-) in that if I run the following
> > query I get out of memory error, and also watching the postgresql process on
> > the box shows the memory consumption continually increasing over time,
> > whilst the query is running.
> >  
> > SELECT crs_feature_name.id, crs_feature_name."type", crs_feature_name.name,
> > crs_feature_name.status, crs_feature_name.other_details,
> > astext(translate(crs_feature_name.shape, 160, 0, 0)) AS shape
> > FROM crs_feature_name
> > inner join crs_parcel on crs_feature_name.id = crs_parcel.fen_id
> > limit 100;
> >  
> > Translate seems to work fine if it's used on its own, but when combining
> > with astext or transform then this is the output (from astext combination
> > anyway).
> > ERROR:  out of memory
> > DETAIL:  Failed on request of size 268435456.
> > 
> > This has only shown up since RC2 as far as I can tell.
> >  
> > Cheers,
> > Bryce.
> 
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