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January 2021

Index Hints

At the end of the previous post on index hints I mentioned that I had been prompted to complete a draft from a few years back because I’d been sent an email by Kaley Crum showing the optimizer ignoring an index_rs_asc() hint in a very simple query. Here, with some cosmetic changes, is the example he sent me.

Index Hints

I’ve lost count of the number of times I’ve reminded people that hinting (correctly) is hard. Even the humble /*+ index() */ hint and its close relatives are open to misunderstanding and accidental misuse, leading to complaints that “Oracle is ignoring my hint”.

Strange though it may seem, I’m still not 100% certain of what some of the basic index hints are supposed to do, and even the “hint report” in the most recent versions of dbms_xplan.display_xxx() hasn’t told me everything I’d like to know. So if you think you know all about hints and indexing this blog note is for you.

I’ll start with a brief, and approximate, timeline for the basic index hints – starting from 8.0

Building Single-Page Websites on WordPress.com

WordPress.com supports a wide range of features for building your online presence: blogs, online stores, newsletter signup forms, and more. These tools are invaluable for many customers, but they can seem excessive for folks who are just looking to create a straightforward single-page website. If that’s you, read on for examples of how you can also create one-page websites here on WordPress.com. 

Both examples use WordPress.com’s freshly-launched Blank Canvas theme, which is optimized for single-page websites. It comes with no header, navigation menus, or widgets, so the page you design in the WordPress editor is the same page you’ll see on the front end. The theme also comes with a handful of ready-made Block Patterns to help kick start your site. 

Video : Long Identifiers in Oracle Database 12.2 Onward

In today’s video we’ll quickly demonstrate long identifiers, introduced in Oracle database 12.2.

The video is based on this article.

Eleven Table Tennis: Basics

Assuming you are an IRL player who wants to get as close to the real thing as possible, that’s what I’d recommend:

New Year … new idea … new channel

I’ve done a lot of presentations over the years, written a ton of blog posts, and over the past  5 years cranked out hundreds of tech videos of my YouTube channel.

But with the current state of the world, I also know that over the last year we’ve been awash with tech content that now comes exclusively over a virtual medium that generally requires us to stop our “day jobs” in order to focus on the content, whether it be a live presentation, recorded video or reading a long form blog post.

Announcing SLOB 2.5.3

This is just a quick blog post to inform readers that SLOB 2.5.3 is now available at the following webpage: click here.

SLOB 2.5.3 is a bug fix release. One of the fixed bugs has to do with how SLOB sessions get connected to RAC instances. SLOB users can surely connect to the SCAN service but for more repeatable testing I advise SLOB 2.5.3 and SQL*Net services configured one per RAC node. This manner of connectivity establishes affinity between schemas and RAC nodes. For example, repeatability is improved if sessions performing SLOB Operations against, say, user7’s schema, it is beneficial to do so connected to the same RAC node as you iterate through your testing.

The following is cut and pasted from SLOB/misc/sql_net/README:

Oracle 19c Automatic Indexing: Non-Equality Predicates Part II (Let’s Spend The Night Together)

In my previous post in this series, I discussed out Automatic Indexing currently does not consider Non-Equality predicates. Automatic Indexing will index columns based only on Equality predicates. So how does Oracle handle the scenario when an SQL has a mixture of both Equality and Non-Equality predicates? I’ll begin by creating two very similar tables, […]

VirtualBox 6.1.18

VirtualBox 6.1.18 has been released.

The downloads and changelog are in the usual places.

I’ve installed it on Windows 10, macOS Big Sur and Oracle Linux 7 hosts with no problems.

I’ll be running new Packer builds for the oraclebase/oracle-7 and oraclebase/oracle-8 vagrant boxes, so they should appear with the new version of the guest additions over the next day or so.

Cheers

Tim…

Links:

Hint Errors

This is a list of possible explanations of errors that you might see in the Hint Report section of an execution plan. It’s just a list of the strings extracted from a chunk of the 19.3 executable around the area where I found something I knew could be reported, so it may have some errors and omissions – but there are plenty of things there that might give you some idea why (in earlier versions of Oracle) you might have seen Oracle “ignoring” a hint: