Description

Returns the amount of space (in bytes) the geometry takes.

This is a nice compliment to PostgreSQL built in functions pg_size_pretty, pg_relation_size, pg_total_relation_size.

	pg_relation_size which gives the byte size of a table may return byte size lower than ST_Mem_Size. This is because pg_relation_size does not add toasted table contribution and large geometries are stored in TOAST tables. pg_total_relation_size - includes, the table, the toasted tables, and the indexes.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and curves

Examples

--Return how much byte space Boston takes up  in our Mass data set
SELECT pg_size_pretty(SUM(ST_Mem_Size(the_geom))) as totgeomsum,
pg_size_pretty(SUM(CASE WHEN town = 'BOSTON' THEN st_mem_size(the_geom) ELSE 0 END)) As bossum,
CAST(SUM(CASE WHEN town = 'BOSTON' THEN st_mem_size(the_geom) ELSE 0 END)*1.00 /
		SUM(st_mem_size(the_geom))*100 As numeric(10,2)) As perbos
FROM towns;

totgeomsum	bossum	perbos
----------	------	------
1522 kB		30 kB	1.99


SELECT ST_Mem_Size(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)'));

---
73

--What percentage of our table is taken up by just the geometry
SELECT pg_total_relation_size('public.neighborhoods') As fulltable_size, sum(ST_Mem_Size(the_geom)) As geomsize,
sum(ST_Mem_Size(the_geom))*1.00/pg_total_relation_size('public.neighborhoods')*100 As pergeom
FROM neighborhoods;
fulltable_size geomsize  pergeom
------------------------------------------------
262144         96238	 36.71188354492187500000
	

See Also