Re: Store TIME in the Oracle

From: Niall Litchfield <niall.litchfield_at_gmail.com>
Date: Mon, 15 Aug 2011 13:20:15 +0100
Message-ID: <CABe10saQsuU-RY9Qa49kUCz6JNoZ-uoTXsA4O2K2vRsk4UaNWQ_at_mail.gmail.com>

I think Norman's test went something like the below (I get a 13% difference on a single run). You are changing the DMY part of the stored data by calling 2 functions. As you never retrieve the stored part of the data then this is surely wasted work. Why not just store the raw date value and then *retrieve* only what you are interested in.

NIALL _at_ NIALL1 >create table t1(
  2 id number,
  3 datecol date,
  4 padding char(500));

Table created.

NIALL _at_ NIALL1 >create table t2(
  2 id number,
  3 datecol date,
  4 padding char(500));

Table created.

NIALL _at_ NIALL1 >set timing on
NIALL _at_ NIALL1 >begin
  2 for i in 1..1000000 loop
  3 insert into t1 (id,datecol,padding)   4 values (i,sysdate,'Record '||i);
  5 end loop;
  6 commit;
  7 end;
  8 /

PL/SQL procedure successfully completed.

Elapsed: 00:03:18.07
NIALL _at_ NIALL1 >ed
Wrote file afiedt.buf

  1 begin
  2 for i in 1..1000000 loop
  3 insert into t2 (id,datecol,padding)   4 values (i,to_date('01-JAN-2000 '||
to_char(sysdate,'HH24:MI:SS'),'DD-MON-YYYY HH24:MI:SS'),'Record '||i);   5 end loop;
  6 commit;
  7* end;
NIALL _at_ NIALL1 >/

PL/SQL procedure successfully completed.

Elapsed: 00:03:48.35
NIALL _at_ NIALL1 >

On Mon, Aug 15, 2011 at 12:44 PM, Eriovaldo Andrietta <ecandrietta_at_gmail.com
> wrote:

> Morning Norman,
>
> The datatype will be DATE., as you said.
> I have interest only on TIME and not in DATE.
>
> I will store it complete as DATE + TIME and retrieve only TIME.
>
> You are right, and I think I am doing as you said, right ?
>
> Regards
> Eriovaldo
>
> On Mon, Aug 15, 2011 at 4:16 AM, Dunbar, Norman (Capgemini) <
> norman.dunbar.capgemini_at_environment-agency.gov.uk> wrote:
>
>> Morning,
>>
>> >> I will follow this way:
>> >>
>> >> to_date('01-JAN-2000 '||
>> >> to_char(sysdate,'HH24:MI:SS'),'DD-MON-YYYY HH24:MI:SS')
>> >>
>> >>
>> >> I will put the date hard code for all lines inserted and the
>> >> time that must be saved.
>>
>> I'm not convinced that that is a good idea. I have a nagging feeling in my
>> head that this will confuse the optimiser if it ever needs to take into
>> account this column in working out a decent query plan.
>>
>> Equally, you'll probably never get the benefit of an index on that column
>> I should imagine - but I suspect you won't be using one anyway.
>>
>> Why not just set your column to sysdate?
>>
>> You will save on one concatenation, on to_char() and one to_date()
>> function call for every insert. As a quick and highly unscientific test, it
>> takes around 23.8% longer to do it your way as compared to sysdate only.
>> Over three runs of 1,000,000 rows inserted. (Very slow PC running Oracle and
>> the database on one single disc.)
>>
>> The date part is irrelevant as you will be selecting only the time part,
>> so why not save some CPU etc?
>>
>> Just my £0.02.
>>
>>
>> Cheers,
>> Norm.
>>
>> Norman Dunbar
>> Contract Senior Oracle DBA
>> Capgemini Database Team (EA)
>> Internal : 7 28 2051
>> External : 0113 231 2051
>>
>>
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>

-- 
Niall Litchfield
Oracle DBA
http://www.orawin.info

--
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Received on Mon Aug 15 2011 - 07:20:15 CDT