[postgis-tickets] [PostGIS] #3716: Gist index irrational growth

[PostGIS]

#3716: Gist index irrational growth
--------------------------------+---------------------
  Reporter:  Marcin Piotrowski  |      Owner:  pramsey
      Type:  defect             |     Status:  new
  Priority:  medium             |  Milestone:
 Component:  postgis            |    Version:  2.1.x
Resolution:                     |   Keywords:
--------------------------------+---------------------
Description changed by pramsey:

Old description:

> etry column).
> The size was not shrinked during autovacuum, only full vacuum was able to
> free the disk space.
>
> This is reproducable using following example that inserts 10000 rows and
> performs 1000 updates on the status column. After that index size is 321
> MB
> (321 MB of indexed nulls ! )
>
> {{{
>
> -- psql script to create the database
>
> CREATE DATABASE gist_weirdness WITH TEMPLATE = template0 ENCODING =
> 'UTF8'
> LC_COLLATE = 'en_US.utf8' LC_CTYPE = 'en_US.utf8';
> \connect gist_weirdness
> CREATE EXTENSION IF NOT EXISTS plpgsql WITH SCHEMA pg_catalog;
> CREATE EXTENSION IF NOT EXISTS postgis WITH SCHEMA public;
> CREATE TABLE table_with_gist (
>     id integer NOT NULL,
>     status character varying(10),
>     geompolygon geometry(Polygon,4326)
> );
> CREATE SEQUENCE table_with_gist_id_seq
>     START WITH 1
>     INCREMENT BY 1
>     NO MINVALUE
>     NO MAXVALUE
>     CACHE 1;
> ALTER TABLE ONLY table_with_gist ALTER COLUMN id SET DEFAULT
> nextval('table_with_gist_id_seq'::regclass);
>
> CREATE INDEX incidents_geompolygon_idx ON table_with_gist USING gist
> (geompolygon);
>

> --  pgscript to insert data
> DECLARE @I;
> set @I = 0;
> while @I < 10000
> begin
> INSERT INTO table_with_gist(status)  VALUES (cast (@I as CHARACTER
> VARYING));
> set @I = @I + 1;
> end
>

> --pgscript to update data
>
> DECLARE @I;
> set @I = 0;
> while @I < 1000
> begin
> update table_with_gist set status=status::integer+7;
> set @I = @I + 1;
> end
>

> }}}

New description:

 If you create a GiST index on a geometry(Polygon,4267) column and do
 updates on the table, the index size grows enormously even if the indexed
 column contains only nulls. This is a big problem that caused index to
 grow to tens of gigabytes for a table with just about 10000 rows, where
 indexed column contained only nulls, but was updated on a minutely basis
 (but not on the geometry column). The size was not shrinked during
 autovacuum, only full vacuum was able to free the disk space.

 This is reproducable using following example that inserts 10000 rows and
 performs 1000 updates on the status column. After that index size is 321
 MB
 (321 MB of indexed nulls ! )

 {{{

 -- psql script to create the database

 CREATE DATABASE gist_weirdness WITH TEMPLATE = template0 ENCODING = 'UTF8'
 LC_COLLATE = 'en_US.utf8' LC_CTYPE = 'en_US.utf8';
 \connect gist_weirdness
 CREATE EXTENSION IF NOT EXISTS plpgsql WITH SCHEMA pg_catalog;
 CREATE EXTENSION IF NOT EXISTS postgis WITH SCHEMA public;
 CREATE TABLE table_with_gist (
     id integer NOT NULL,
     status character varying(10),
     geompolygon geometry(Polygon,4326)
 );
 CREATE SEQUENCE table_with_gist_id_seq
     START WITH 1
     INCREMENT BY 1
     NO MINVALUE
     NO MAXVALUE
     CACHE 1;
 ALTER TABLE ONLY table_with_gist ALTER COLUMN id SET DEFAULT
 nextval('table_with_gist_id_seq'::regclass);

 CREATE INDEX incidents_geompolygon_idx ON table_with_gist USING gist
 (geompolygon);


 --  pgscript to insert data
 DECLARE @I;
 set @I = 0;
 while @I < 10000
 begin
 INSERT INTO table_with_gist(status)  VALUES (cast (@I as CHARACTER
 VARYING));
 set @I = @I + 1;
 end


 --pgscript to update data

 DECLARE @I;
 set @I = 0;
 while @I < 1000
 begin
 update table_with_gist set status=status::integer+7;
 set @I = @I + 1;
 end


 }}}

--

--
Ticket URL: <https://trac.osgeo.org/postgis/ticket/3716#comment:2>
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