Re: ERROR: invalid input syntax for type date: IS IT A BUG here?

On 08/21/2015 02:32 PM, AI Rumman wrote:
> Hi All,
>
> I am using Postgresql 9.1  where have a partitioned table as below:
>
>     events_20150101
>     events_20150102
>     events_20150103
>     ...
>     events_overflow
>
>
> When I am running the following query it gives me result:
>
> *SQL 1: *
>
>     select all relname, pg_total_relation_size(relname::text) as s,
>     substr(relname,18)::date as dt from pg_stat_user_tables where
>     schemaname = 'partitions' and relname not like '%overflow'
>

What is the result?

>
> But when I run the following one, it gives me error:
>
> *SQL 2: *
>
>     select * as ts
>     from
>     (
>     select relname, pg_total_relation_size(relname::text) as s,
>     substr(relname,18)::date as dt from pg_stat_user_tables where
>     schemaname = 'partitions' and relname not like '%overflow'  order by
>     pg_total_relation_size(relname::text) desc
>     ) as q
>     where dt = '2015-01-01'::date;
>     *ERROR:  invalid input syntax for type date: ""*


production=# select substr('events_20150101', 18);
  substr
--------

(1 row)

production=# select substr('events_20150101', 18)::date;
ERROR:  invalid input syntax for type date: ""

Your substr is creating an empty str which cannot be cast to a date. I
can't see how you could get a result from your first query, which is why
I asked for what you are seeing.

>
> However, explain is showing plan:
>
>       Sort  (cost=202.03..202.04 rows=1 width=64)
>         Sort Key:
>     (pg_total_relation_size(((pg_stat_all_tables.relname)::text)::regclass))
>         ->  Subquery Scan on pg_stat_all_tables  (cost=201.93..202.02
>     rows=1 width=64)
>               ->  HashAggregate  (cost=201.93..201.99 rows=1 width=136)
>                     ->  Nested Loop Left Join  (cost=0.00..201.92 rows=1
>     width=136)
>                           ->  Nested Loop  (cost=0.00..194.23 rows=1
>     width=132)
>                                 Join Filter: (c.relnamespace = n.oid)
>                                 ->  Seq Scan on pg_namespace n
>     (cost=0.00..1.39 rows=1 width=68)
>                                       Filter: ((nspname <> ALL
>     ('{pg_catalog,information_schema}'::name[])) AND (nspname !~
>     '^pg_toast'::text) AND (nspname = 'partitions'::name))
>                                 ->  Seq Scan on pg_class c
>     (cost=0.00..192.77 rows=6 width=72)
>                                       Filter: ((relkind = ANY
>     ('{r,t}'::"char"[])) AND (relname !~~ '%overflow'::text) AND
>     ((substr((relname)::text, 18))::date = '2015-01-01'::date))
>                           ->  Index Scan using pg_index_indrelid_index
>     on pg_index i  (cost=0.00..7.66 rows=2 width=8)
>                                 Index Cond: (c.oid = indrelid)
>
> Again, if I create a table and run the query it runs:
>
> *SQL 3:*
>
>     create table dba.tbl_list as  select all relname,
>     pg_total_relation_size(relname::text) as s, substr(relname,18)::date
>     as dt from pg_stat_user_tables where schemaname = 'partitions' and
>     relname not like '%overflow' ;
>     SELECT 558
>
>     \d+ dba.tbl_list
>                       Table "dba.tbl_list"
>       Column  |  Type  | Modifiers | Storage | Description
>     ---------+--------+-----------+---------+-------------
>       relname | name   |           | plain   |
>       s       | bigint |           | plain   |
>       dt      | date   |           | plain   |
>     Has OIDs: no
>
>
> *SQL 4:*
>
>     select * from dba.tbl_list  where dt = '2015-01-01';
>                relname          |     s      |     dt
>     ---------------------------+------------+------------
>       events_20150101 | 1309966336 | 2015-01-01
>     (1 row)
>
> Why the 2nd query is showing error? Is it a bug? Or am I doing any silly?
> Any advice, please.
>
> Thanks & Regards.


--
Adrian Klaver
adrian.klaver@aklaver.com