Getting an error while running rake command on a rails 2 project with postgres and postgis

Hi All,

I am runnning a rails 2 project with the following gems, georuby,
spatial_adapter. And Postgres db as backend. But I am facing this error.
I tired installing postgis also but still get this. Any ideas what i
should try. This is a rails 2.3 project ,so is it some version
requirements i am missing. The statement seems to be correct and i tied
looking it up too. Please help.

[root@localhost webapp]# rake db:migrate
(in /root/mysite/webapp)
==  CreatePlaces: migrating

===================================================
– create_table(:places, {:id=>false})
-> 0.0030s
– execute(“alter table places add primary key (id)”)
NOTICE: ALTER TABLE / ADD PRIMARY KEY will create implicit index
“places_pkey” for table “places”
-> 0.1144s
– execute(“select AddGeometryColumn(‘public’, ‘places’,
‘point_geometry’, 4326, ‘POINT’, 3)”)
rake aborted!
An error has occurred, this and all later migrations canceled:

PGError: ERROR:  function addgeometrycolumn(unknown, unknown,

unknown, integer, unknown, integer) does not exist
LINE 1: select AddGeometryColumn(‘public’, ‘places’,
'point_geometry…
^
HINT: No function matches the given name and argument types. You
might need to add explicit type casts.
: select AddGeometryColumn(‘public’, ‘places’, ‘point_geometry’,
4326, ‘POINT’, 3)

Thanks