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Home -> Community -> Mailing Lists -> Oracle-L -> RE: RE: How do you generate primary keys?
I believe you can pin the sequences to help stop this - see Ixora's http://www.ixora.com.au/scripts/library.htm and keep_sequences.sql
and also unload_sequences.sql
"This script unloads all cached sequence numbers from the library cache, by temporarily marking them as NOCACHE. This script is intended to be used prior to shutdown in single-instance Oracle, to prevent the loss of cached sequence numbers, should a SHUTDOWN ABORT become necessary. "
Haven't tried this, but thought it could be useful.
HTH,
Bruce Reardon
Specialist - Technical Systems
mailto:bruce.reardon_at_comalco.riotinto.com.au
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-----Original Message-----
Sent: Thursday, 6 November 2003 9:24 AM
To: Multiple recipients of list ORACLE-L
If the sequence migrates out of cache, gaps will occur as well.
Ian MacGregor
Stanford Linear Accelerator Center
ian_at_slac.stanford.edu
-----Original Message-----
Sent: Wednesday, November 05, 2003 12:59 PM
To: Multiple recipients of list ORACLE-L
rollbacks?
-----Original Message-----
Cary Millsap
Sent: Wednesday, November 05, 2003 3:39 PM
To: Multiple recipients of list ORACLE-L
I've heard of people using instance startup triggers to insert VOID records in cases where there are gaps. I haven't thought about it much recently, but I can't presently think of occasions when gaps occur other than instance shutdown.
Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
Upcoming events:
- Performance Diagnosis 101: 11/19 Sydney - SQL Optimization 101: 12/8-12 Dallas - Hotsos Symposium 2004: March 7-10 Dallas - Visit www.hotsos.com for schedule details...
-----Original Message-----
Jamadagni, Rajendra
Sent: Wednesday, November 05, 2003 12:14 PM
To: Multiple recipients of list ORACLE-L
Ryan,
hypothetically, When you have a requirement that no gaps allowed in a sequence no matter what, would you still use sequences?
Raj
-----Original Message-----
Sent: Wednesday, November 05, 2003 12:09 PM
To: Multiple recipients of list ORACLE-L
do people actually use a table as a counter these days? Now Im 'assuming' they are jsut people who dont know about sequences or are there actually 'professionals' who know about sequencse and decide not to use them.
id assume those tables were used in oracle 5 days because either sequences didnt exist or they werent designed well?
>
> From: "Cary Millsap" <cary.millsap_at_hotsos.com>
> Date: 2003/11/05 Wed AM 11:04:25 EST
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> Subject: RE: How do you genrate primary keys?
>
> "Hit a table that keeps a counter" will not scale (will not perform at
> high concurrency). It will cause you no end of "buffer busy waits"
> waits, "latch free" waits for a cache buffers chains latch (even if
> db_block_buffers, _db_block_hash_buckets, and _db_block_hash_latches
> could be set to infinity), lots of unnecessary CPU service consumption
> due to the spinning (especially if you try to tinker with
_spin_count),
> and possibly a wide range of side effects including "write complete
> waits" waits and others.
>
>
> Cary Millsap
> Hotsos Enterprises, Ltd.
> http://www.hotsos.com
>
> Upcoming events:
> - Performance Diagnosis 101: 11/19 Sydney
> - SQL Optimization 101: 12/8-12 Dallas
> - Hotsos Symposium 2004: March 7-10 Dallas
> - Visit www.hotsos.com for schedule details...
>
>
> -----Original Message-----
> Hemant K Chitale
> Sent: Wednesday, November 05, 2003 8:25 AM
> To: Multiple recipients of list ORACLE-L
>
>
> My comments [probably off-the-cuff without spending much time thinking
> the issues through .....?]
>
> 1. Hit a table that keeps a counter.
> Used to be a mechanism in the Oracle5 days [If I remember correctly,
> Sequences came in Oracle6]. Issues were with locking the single
> record used as the generator or scanning for the max(value) of the
> key. Not quite sure I understand how you encountered concurrency
> issues, though.
>
>
> 2. Stored sequences.
> Although I prefer not to use a Sequence as a PK in itself [preferring
> natural column/s which are Unique keys, with the NOT NULL, of course],
> I have used a Sequence in an Advanced Replication implementation that
> had no Primary Key and I needed a PK for Conflict Resolution [this was
> years ago and, if you ask me, I can't remember all the details]
>
> 3. SYS_GUID
> SYS_GUID I've never used. It doesn't generate a NUMBER value so it is
> not really similar to a Sequence. Can user's key in a
> SYS_GUID-generated value ? Is it really "human readable" or
> "recallable" as a plain NUMBER, Security Security Number,
> ZIP Code ??
>
> 4. Similar to SYS_GUID ..
> You hit on a fortuitous combination of columns.
>
>
> Hemant
>
> At 05:19 AM 05-11-03 -0800, you wrote:
> >The recent article that mentioned sequences got me to thinking. I
> >might pitch a more detailed article on sequences to Builder.com. But
> >a more interesting article might be one that explored various ways to
> >automatically generate primary keys. So, in the name of research, let
> >me throw out the following questions:
> >
> >What mechanisms have you used to generate primary keys? Which ones
> >worked well, and why? Which mechanisms worked poorly?
> >
> >I've run up against the following approaches:
> >
> >* Hit a table that keeps a counter. This is the "roll your own
> >sequence method". The one time I recall encountering this approach, I
> >helped convert it over to using stored sequences. This was because of
> >concurrency problems: with careful timing, two users could end up
> >with the same ID number for different records. Is there ever a case
> >when this roll-your-own approach makes sense, and is workable?
> >
> >* Stored sequences. I worked on one app that used a separate sequence
> >for each automatically generated primary key. I worked on another
> >app, a smaller one, that used the same sequence for more than one
> >table. The only issue that I recall is that sometimes numbers would
> >be skipped. But end users really didn't care, or even notice.
> >
> >* The SYS_GUID approach. I've never used SYS_GUID as a primary key
> >generator. I wonder, was that Oracle's motivation for creating the
> >function? Has anyone used it for primary keys in a production app?
> >What's the real reason Oracle created this function?
> >
> >* Similar to SYS_GUID, I once worked on an obituary-tracking
> >application that built up a primary key from, as best I can recall
> >now: date of death, part of surname, part of first name, and a
> >sequence number used only to resolve collisions, of which there were
> >few. The approached worked well, actually, because whatever fields we
> >munged together to generate a primary key gave us a unique key the
> >vast majority of the time.
> >
> >The SYS_GUID approach is interesting, but if you need an ID number
> >that users will see, and that users might type in themselves (e.g.
> >social security number), is SYS_GUID really all that viable?
> >
> >Best regards,
> >
> >Jonathan Gennick --- Brighten the corner where you are
-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Reardon, Bruce (CALBBAY) INET: Bruce.Reardon_at_comalco.riotinto.com.au Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Wed Nov 05 2003 - 16:39:30 CST
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