Hi Adrian,
Thanks for replying here.
Actually, I modified the actual table name from my production where I forgot to change the subtr value.
You can see the result "SELECT 558" in SQL 3 where it selected that many rows.
Regards.
On Fri, Aug 21, 2015 at 3:13 PM, Adrian Klaver <adrian.klaver@xxxxxxxxxxx> wrote:
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.
*SQL 3:*
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:
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@xxxxxxxxxxx
