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E-rows / A-rows

This note was prompted by an error I made at the UKOUG TechFest19 yesterday. It’s fairly well-known that when you read an execution plan that includes the rowsource execution stats – so you get the E-rows (estimated) and A-rows (Actual) reported – then a sensible check of the quality of the optimizer’s calculations is to compare the estimates and actuals allowing for the fact that the E-rows is “per start” and the A-rows is “cumulative”, so A-rows = E-rows * Starts.

The error I made yesterday was to forget that this relationship isn’t always true. In particular partitioning and parallel query introduced the need to be a little flexibility in reading the numbers – which I’ll demonstrate with a coupld of simple examples running under 12.2.0.1

Video : SQLcl and Oracle REST Data Services (ORDS)

In today’s video we’ll demonstrate the ORDS functionality built into Oracle SQLcl.

This is based on this article.

There are loads of other ORDS articles here.

The star of today’s video is Arman Sharma, captured at Sangam 2015. Seems like yesterday.

Cheers

Oracle Cloud : Free Tier and Article Updates

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Oracle Cloud Free Tier was announced a couple of months ago at Oracle OpenWorld 2019. It was mentioned in one of my posts at the time (here). So what do you get for your zero dollars?

Video : Oracle REST Data Services (ORDS) : OAuth Implicit

In today’s video we look at the OAuth Implicit flow for Oracle REST Data Services.

This goes together with a previous video about first-party authentication here.

Both videos are based on parts of this article.

There are loads of other ORDS articles here.

Oracle Database 18c and 19c on Fedora 31

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Fedora 31 was released a couple of weeks ago and I’ve done some Oracle installations on it.

Just a warning to explain why this is a bad idea for anything real.

With that out of the way, here are the articles.

Announcing Obfuscated Column Data Loading with SLOB

On November 18, 2019 I announced availability of SLOB 2.5.2. It is primarily a small bug fix release but also has an undocumented new feature. I want to say a few words about the feature in this post and will update SLOB with full support (e.g., documentation and slob.conf parameter support) in SLOB 2.5.3.  Some SLOB users might want this new undocumented feature as soon as possible–thus this blog post.

Announcing SLOB 2.5.2

SLOB 2.5.2 is available for download from Github. Please visit the SLOB Resources Page for the download URLs.

SLOB 2.5.2 is a bug fix release.

Parse Time

This is a note I started drafting In October 2012. It’s a case study from an optimizer (10053) trace file someone emailed to me, and it describes some of the high-level steps I went through to see if I could pinpoint what the optimizer was doing that fooled it into spending a huge amount of time optimising a statement that ultimately executed very quickly.

Unfortunately I never finished my notes and I can no longer find the trace file that the article was based on, so I don’t really know what I was planning to say to complete the last observation I had recorded.

Library Cache Stats

In resonse to a comment that one of my notes references a call to a packate “snap_libcache”, I’ve posted this version of SQL that can be run by SYS to create the package, with a public synonym, and privileges granted to public to execute it. The package doesn’t report the DLM (RAC) related activity, and is suitable only for 11g onwards (older versions require a massive decode of an index value to convert indx numbers into names).

Video : Oracle REST Data Services (ORDS) : Database Authentication

Today’s video is a run through the Database Authentication functionality in Oracle REST Data Services (ORDS).

As always, this is based on an article on the same subject.

There are better methods of authentication and authorization available from ORDS, which you can read about here.