USING bug
The Oracle Developer Community forum often sees SQL that is hard to read – sometimes because it’s a brutal tangle of subqueries, sometimes because the format it bad, sometimes because the use of table...
View ArticleOrder By
This is a brief note with an odd history – and the history is more significant than the note. While searching my library for an example of an odd costing effect for the “order by” clause I discovered a...
View ArticleCase and Aggregate bug
The following description of a bug appeared on the Oracle Developer Community forum a little while ago – on an upgrade from 12c to 19c a query starting producing the wrong results on a simple call to...
View ArticleFlashback Bug
Here’s a problem with the “flashback versions” technology that showed up at the end of last week. There’s a thread about it on the Oracle Developer community forum, and a chain of tweets that was my...
View ArticleIndex FFS Cost
There are a number of unexpected issues with the optimizer’s treatment of the index fast full scan, the access path where Oracle ignores the structure of the B-tree and uses multiblock reads to do a...
View ArticleIndex FFS Cost 2
Here’s a little puzzle, highlighting a “bug that’s not a bug” that was “fixed but not fixed” some time in the 10.2 timeline. (If you want specifics about exactly when the fix became available and what...
View ArticleJoin Elimination redux
This note is a followup to a post from a few years back (originally dating further back to 2012) where I described an inconsistency that appeared when join elimination and deferrable constraints...
View ArticleHex tip
A surprising amount of the work I do (or used to do) revolves around numbers; and once I’m outside the realm of the optimizer (i.e. getting away from simple arithmetic), one of the bits of playing...
View ArticleGTT LOBs
Searching my blog recently for some details about a temporary space problem I came across a draft I’d written a few years ago about LOBs in global temporary tables. It was a summary of an exchange from...
View ArticleHappy New Year
Here’s an entertaining little bug that appeared on the oracle-l list server just in time to end one year and start another in a suitable way. The thread starts with an offering from Matthias Rogel...
View ArticleUpgrade Surprise
Here’s a little surprise that showed up in the most recent (March 2022) article that I sent to Simpletalk for the series on transformations. I had been using 19c (19.11.0.0) to create and run my...
View ArticleDrop column bug
Here’s a problem that appeared recently on the Orace Developer forum showing one of the classic symptons of new features namely that “mix and match” often runs into problems. This example has been a...
View ArticleDrop column bug
In the previous note about a problem dropping virtual columns the “guilty party” that made it impossible to drop any columns was based on a complex data type owned by the MDSYS (Spatial) schema. This...
View Articleredefinition error
Here’s a note about a data error generated by using (possibly mis-using) the dbms_redefinition package (jump to conclusion). The original code to demonstrate the problem comes from a note on the...
View ArticleLag/Lead slow
This note is about a surprising performance difference between the lead() and lag() analytic functions (which31 turns out to be due to the behaviour of the nth_value() function) when the option to...
View ArticleJoin View delete
I’ve written a couple of notes about deleting from join views and (ultimately) the fact that if you have muliple key-preserved tables in join view then the first key preserved table in the from clause...
View Articledrop t/s bug
A recent thread on the MOS database admin forum (needs an account) demonstrated a number of little issues with bugs, debugging, complex syntax, and the never-ending list of “not quite complete” code...
View ArticleEncryption oddity
Here’s a strange problem (with possible workaround) that appeared in a thread on the Oracle developer forum a couple of days ago. It looks like the sort of problem that might be a memory overflow...
View ArticleCase Study
A recent post on the Oracle SQL and PL/SQL forum posted the following query with a complaint that it produced the wrong results: select count(*) from all_synonyms left join all_objects b on...
View ArticleDescending max()
I’ve written a few notes about problems with “descending” indexes in the past (the word is in quotes because it’s not the index that’s defined as descending, it’s a proper subset of the columns of the...
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