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Index Sorting 26 Aug 2013 | 11:48 am
From time to time I’ve mentioned the fact that the optimizer will sort indexes alphabetically by name as the last tie-breaker when two plans have the same cost. Thanks to an email that arrived a coupl...
12c join defect 24 Aug 2013 | 04:47 pm
This is a brief, temporary, note to draw attention to an item I wrote about 3 years ago demonstrating an anomaly with the plan Oracle could produce if the order of predicates in your where clause chan...
Distributed Queries – 3 19 Aug 2013 | 11:25 am
A comment I’ve made many times in the past about distributed queries is that Oracle doesn’t try to retrieve histogram information from remote databases when optimizing a query. Checking back through p...
MV Refresh 15 Aug 2013 | 10:12 pm
Here’s a funny little problem I came across some time ago when setting up some materialized views. I have two tables, orders and order_lines, and I’ve set up materialized view logs for them that allow...
NVL() 13 Aug 2013 | 11:14 am
Here’s a little detail that I hadn’t noticed before (and it goes back to at least 8i). This is running on 11.2.0.3, and table t1 is just all_objects where rownum <= 20000: The optimizer seems to have...
12c Join Views 9 Aug 2013 | 10:36 pm
There are a couple of posts on the blog describing problems with updateable join views or, to be more precise, join views which were key-preserved but which the optimizer did not recognize as key-pres...
Manuals 9 Aug 2013 | 02:03 pm
Just glancing through the 12c manuals (Server Reference 12.1 June 2013 – E17615-16) to check a particular database limit, I came across the following: “Services – maximum per instance – 115″. That’s a...
12c subquery factoring 6 Aug 2013 | 12:08 pm
I’ve written a few notes about anomalies in subquery factoring (with subquery) in the past, principally making a fuss about the fact that moving an inline view into a “with subquery” can cause a plan ...
Interview 6 Aug 2013 | 10:59 am
The interview I did with Timur Akhmadeev while visiting Moscow is now online. 90 minutes ! Just got through the first 6 minutes and haven’t embarrassed myself yet: http://timurakhmadeev.wordpress.com/...
12 notes 6 Aug 2013 | 10:49 am
This is just a temporary note to advertise the fact that I’ve added Steve Karam’s collation of blog links on 12c features to the top of the list of links to the right of the page (12c Notes).
