Comments on: The Three Pillars of Oracle Data Warehousing http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/ Oracle Data Warehouse Design and Architecture Fri, 04 Jul 2008 18:47:32 +0000 http://wordpress.org/?v=MU By: A metablog… | El Mundo Con Otros Ojos http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-51071 A metablog… | El Mundo Con Otros Ojos Wed, 25 Jun 2008 22:01:37 +0000 https://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-51071 [...] data warehousing techniques and other things both Oracle and non-Oracle related. He needs to learn how to spell – but does all right most of the [...] [...] data warehousing techniques and other things both Oracle and non-Oracle related. He needs to learn how to spell – but does all right most of the [...]

]]> By: infonitive http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-51029 infonitive Mon, 26 May 2008 00:32:19 +0000 https://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-51029 Interesting views on data warehousing. You might find www.infonitive.com an interesting forum. Interesting views on data warehousing. You might find http://www.infonitive.com an interesting forum.

]]> By: Jonathan Lewis http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1064 Jonathan Lewis Sun, 28 May 2006 10:29:00 +0000 https://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1064 "why isn't query-rewrite automatic" It's all in the way you read the text. As you pointed out, there's an optional clause that you can put in the mview definition. What I wrote was "Then create a materialized view with query rewrite enabled" - i.e. create a materialized view with that optional clause in place. “why isn’t query-rewrite automatic”

It’s all in the way you read the text.

As you pointed out, there’s an optional clause that you can put in the mview definition. What I wrote was “Then create a materialized view with query rewrite enabled” - i.e. create a materialized view with that optional clause in place.

]]> By: David Weigel http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1063 David Weigel Fri, 26 May 2006 22:16:00 +0000 https://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1063 <I>with query rewrite enabled...</I> I'm sure I'm missing something obvious, but why isn't query-rewrite automatic? There's a special grant the user needs, and there's a clause to put in the mview defintion. When would you turn query-rewrite <I>off</I>? with query rewrite enabled…

I’m sure I’m missing something obvious, but why isn’t query-rewrite automatic? There’s a special grant the user needs, and there’s a clause to put in the mview defintion. When would you turn query-rewrite off?

]]> By: David Aldridge http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1062 David Aldridge Sun, 21 May 2006 08:50:00 +0000 https://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1062 Along a similar line, having two summary tables with exactly the same data but with different partitioning schemes is a useful technique. Query rewrite is very happy to pick the appropriate one to use. Along a similar line, having two summary tables with exactly the same data but with different partitioning schemes is a useful technique. Query rewrite is very happy to pick the appropriate one to use.

]]> By: Jonathan Lewis http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1061 Jonathan Lewis Sat, 20 May 2006 10:28:00 +0000 https://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1061 Pete, True: any attempt at clustering is likely to be a benefit along just one dimension - but it's always worth checking if there's one dimension that's worth the effort, so long as it doesn't cause too much disruption elsewhere. There's also the option that you can cluster in a second dimension by copying the data in a different order, e.g. create table t2 as select * from t1 order by colx Then create a materialized view with query rewrite enabled so that queries against t1 can visit t2. It's not a strategy that I've used often - but it's just a special case of a summary table, and disks are just so big these days you need something to fill the space with to stop other people from interfering. Regards Jonathan Lewis Pete,

True: any attempt at clustering is likely to be a benefit along just one dimension - but it’s always worth checking if there’s one dimension that’s worth the effort, so long as it doesn’t cause too much disruption elsewhere.

There’s also the option that you can cluster in a second dimension by copying the data in a different order, e.g.

create table t2 as
select * from t1
order by colx

Then create a materialized view with query rewrite enabled so that queries against t1 can visit t2.

It’s not a strategy that I’ve used often - but it’s just a special case of a summary table, and disks are just so big these days you need something to fill the space with to stop other people from interfering.

Regards
Jonathan Lewis

]]> By: Pete_S http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1060 Pete_S Sat, 20 May 2006 07:45:00 +0000 https://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1060 Clustering (with or with out the P) can be problematic - we can only really cluster on one dimension (perhaps a couple if there is some correlation between them – say a brewer supplies products that are beers!) but when you try to cluster product, location and customer… Clustering (with or with out the P) can be problematic - we can only really cluster on one dimension (perhaps a couple if there is some correlation between them – say a brewer supplies products that are beers!) but when you try to cluster product, location and customer…

]]> By: David Aldridge http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1059 David Aldridge Fri, 19 May 2006 09:58:00 +0000 https://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1059 Note to self: don't go swimming with Pete :D DB: yes, I think if I had to pick just one of those three techniques it would be summaries. There's nothing like making a scan of 100,000,000 fact table records return in 0.01 seconds for brightening your day. JL: Maybe Pack, Parcel or Pigeonhole would also be psuitable. Note to self: don’t go swimming with Pete :D

DB: yes, I think if I had to pick just one of those three techniques it would be summaries. There’s nothing like making a scan of 100,000,000 fact table records return in 0.01 seconds for brightening your day.

JL: Maybe Pack, Parcel or Pigeonhole would also be psuitable.

]]> By: Jonathan Lewis http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1058 Jonathan Lewis Fri, 19 May 2006 09:30:00 +0000 https://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1058 You could add Placement, Postition, or possibly just Psorting - as another strategy for optimising physical colocation of data. (I don't think you can get away with claiming a silent P in Pclustering, otherwise that would do as the more generic description). Jonathan Lewis You could add Placement, Postition, or possibly just Psorting - as another strategy for optimising physical colocation of data. (I don’t think you can get away with claiming a silent P in Pclustering, otherwise that would do as the more generic description).

Jonathan Lewis

]]> By: Anonymous http://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1057 Anonymous Fri, 19 May 2006 07:47:00 +0000 https://oraclesponge.wordpress.com/2006/05/18/the-three-pillars-of-oracle-data-warehousing/#comment-1057 Don, Why you think it is tough without MV's and rollups?. Could you please give an example? Don,

Why you think it is tough without MV’s and rollups?. Could you please give an example?

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