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?