functions, selects and the planner

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In PostgreSQL 8.3 lets say I have a table:

create table t(c1 int, c2 int, ts0 timestamp with time zone, ts1 timestamp
with time zone, data varchar);

an index:

create index t_c1_c2_ts0_idx on t using btree(c1, c2, ts0 desc);

and a function:

create function f(_ts timestamp(0) with time zone, _c1 int, _c2 int)
returns
varchar as $$
declare
  _data varchar := null;
begin
  select into _data data from t where _ts >= ts0 and c1 = _c1 and c2 = _c2
and (ts1 is null or _ts < ts1);
  return _data;
end
$$ language plpgsql;

My question is when is the "select into _data" query planned/replanned? 
I'm
concerned that the query might only be planned once (e.g. the first time
it's executed or when the function is first defined) and cached
indefinitely.  The table t is initially empty, but grows at a fairly
steady
rate over time.  So if the table is essentially empty when the query is
planned, a seqscan is certainly what the planner would do.  However, as
time
goes on and table t is filled with data and the stats change, will the
query
eventually be replanned?  If not, what are some suggested ways to handle
this?

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In PostgreSQL 8.3 lets say I have a table:<br><br>create table t(c1 int,
c2 int, ts0 timestamp with time zone, ts1 timestamp with time zone, data
varchar);<br><br>an index:<br><br>create index t_c1_c2_ts0_idx on t using
btree(c1, c2, ts0 desc);<br>
<br>and a function:<br><br>create function f(_ts timestamp(0) with time
zone, _c1 int, _c2 int) returns varchar as $$<br>declare<br>&nbsp; _data
varchar := null;<br>begin<br>&nbsp; select into _data data from t where
_ts &gt;= ts0 and c1 = _c1 and c2 = _c2 and (ts1 is null or _ts &lt;
ts1);<br>
&nbsp; return _data;<br>end<br>$$ language plpgsql;<br><br>My question is
when is the &quot;select into _data&quot; query planned/replanned?&nbsp;
I&#39;m concerned that the query might only be planned once (e.g. the
first time it&#39;s executed or when the function is first defined) and
cached indefinitely.&nbsp; The table t is initially empty, but grows at a
fairly steady rate over time.&nbsp; So if the table is essentially empty
when the query is planned, a seqscan is certainly what the planner would
do.&nbsp; However, as time goes on and table t is filled with data and the
stats change, will the query eventually be replanned?&nbsp; If not, what
are some suggested ways to handle this?<br>
<br>

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