IDS Forum

Re: Rowid concept.

Posted By: Malc_p
Date: Wednesday, 10 September 2003, at 3:46 a.m.

In Response To: RE: Rowid concept. (KOLAYA, SCOTT M)

Only if the table is created without specifying rowids. It works if you do an ALTER TABLE ... ADD ROWIDS.

On Tue, 9 Sep 2003 13:44:59 -0400 , KOLAYA, SCOTT M wrote:
>Does that problem exist even if you create the fragmented table with rowids,
>or just when you fragment it without specifying with rowids?
>
>Scott
>
>-----Original Message-----
>From: Malc_p [mailto:malc_p@btinternet.com]
>Sent: Tuesday, September 09, 2003 3:45 AM
>To: KOLAYA, SCOTT M
>Cc: ids@iiug.org
>Subject: Re: Rowid concept. [1810]
>
>
>Further to this; there's an ongoing problem with ISQL and forms on
>fragmented
>tables in that you can't run a form on a fragmented table without rowids.
>Another outstanding request from ages ago.
>(This is still present on IDS9.30 with ISQL 7.31)
>
>
>On Mon, 8 Sep 2003 14:20:55 -0400 (EDT), KOLAYA, SCOTT M wrote:
>>Ravi,
>>
>>The rowid is a 4-byte code made up of the logical page number as the 3
>first
>>significant bytes and the slot number within that page as the least
>>significant byte. So to answer your question, Informix doesn't need to
>>"generate" the rowid because it represents the location of the actual row.
>>rowids are not unique for fragmented tables, because the logical page is
>>only unique to a fragment. For this reason, when you fragment a table and
>>try to select from it by rowid, the engine will give you a rowid doesn't
>>exist message. To get around the issue with older apps still using rowid,
>>Informix implemented a create table with rowid syntax. Although Informix
>>recommends using primary keys instead of rowids. rowid is not maintained
>if
>>the row is deleted and re-inserted (some applications do this instead of
>>updating). Alterations to the table can affect rowid. For example, change
>>in fragment strategies, clustering, etc. Any operation that moves the row
>>from it's logical location will change the rowid.
>>
>>That being said, Good Luck,
>>
>>Scott Kolaya
>>
>>-----Original Message-----
>>From: N Ravishank.... [mailto:W2925C@motorola.com]
>>Sent: Monday, September 08, 2003 1:30 AM
>>To: ids@iiug.org
>>Subject: Rowid concept. [1809]
>>
>>
>>Hi,
>>
>>We are planning to fetch the data from set of tables by using rowids only
>>(no other conditions in the 'where' clause).
>>
>>How Informix is generating rowids for each and every row inserted into
>>Informix table?
>>Is Informix using any sys tables to generate unique rowids for every
>>inserted row?
>>
>>Thanks in advance.
>>
>>Regards,
>>Ravi Shankar N.
>>
>>
>>
>
>--
>Malc_p
>
>--
>XS2Mail: Check your mail anywhere
>http://www.xs2mail.com/
>

--
Malc_p

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Messages In This Thread

• Rowid concept.
  N Ravishankar-W2925C -- Monday, 8 September 2003, at 1:29 a.m.
  • RE: Rowid concept.
    KOLAYA, SCOTT M -- Monday, 8 September 2003, at 2:20 p.m.
    • Re: Rowid concept.
      Malc_p -- Tuesday, 9 September 2003, at 3:49 a.m.
    • RE: Rowid concept.
      KOLAYA, SCOTT M -- Tuesday, 9 September 2003, at 1:48 p.m.
    • Re: Rowid concept.
      Malc_p -- Wednesday, 10 September 2003, at 3:46 a.m.

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