问题：一些错误的日期数据，导致to_date报错
例如：
select to_date('20230230','yyyymmdd')
SQL 错误[22008]: ERROR: date/time field value out of range: "202302300"
根据日期的规则，做了简单的验证，将超出范围的转为当月最大值（前提是要保证业务可以接受）
create or replace function to_date_advanced(in_date text)
returns date as $$
declare
out_date date;
var_date text;
begin
select
case when
substring(in_date,5,2) in ('01','03','05','07','08','10','12')
and substring(in_date,7,2)::int > 31
then
substring(in_date,1,6)||'31'
when
substring(in_date,5,2) in ('04','06','09')
and substring(in_date,7,2)::int > 30
then
substring(in_date,1,6)||'30'
when
substring(in_date,5,2) = '02'
and substring(in_date,1,4)::int%4 = 0
and substring(in_date,7,2)::int > 29
then
substring(in_date,1,6)||'29'
when
substring(in_date,5,2) = '02'
and substring(in_date,1,4)::int%4 <> 0
and substring(in_date,7,2)::int > 28
then
substring(in_date,1,6)||'28'
else
in_date
end into var_date;
select
to_date(case when
substring(var_date,5,2)::int > 12
then
substring(var_date,1,4)||'12'||substring(var_date,7,2)
else
var_date
end,'yyyymmdd') into out_date;
return out_date;
end; $$ language plpgsql;
