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RDBMS

RDBMS (vs. NoSQL) scales the algorithm before the hardware

By Franck Pachot

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In The myth of NoSQL (vs. RDBMS) “joins dont scale” I explained that joins actually scale very well with an O(logN) on the input tables size, thanks to B*Tree index access, and can even be bounded by hash partitioning with local index, like in DynamoDB single-table design. Jonathan Lewis added a comment that, given the name of the tables (USERS and ORDERS). we should expect an increasing number of rows returned by the join.

In this post I’ll focus on this: how does it scale when index lookup has to read more and more rows. I’ll still use DynamoDB for the NoSQL example, and this time I’ll do the same in Oracle for the RDBMS example.

A lesson from NoSQL (vs. RDBMS): listen to your users

By Franck Pachot

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I have written a few blog posts about some NoSQL (vs. RDBMS) myths (“joins dont scale”, “agility: adding attributes” and “simpler API to bound resources”). And I’ll continue on other points that are claimed by some NoSQL vendors and are, in my opinion, misleading by lack of knowledge and facts about RDBMS databases. But here I’m sharing an opposite opinion: SQL being user-friendly is now a myth.

The myth of NoSQL (vs. RDBMS) agility: adding attributes

By Franck Pachot

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There are good reasons for NoSQL and semi-structured databases. And there are also many mistakes and myths. If people move from RDBMS to NoSQL because of wrong reasons, they will have a bad experience and this finally deserves NoSQL reputation. Those myths were settled by some database newbies who didn’t learn SQL and relational databases. And, rather than learning the basics of data modeling, and capabilities of SQL for data sets processing, they thought they had invented the next generation of persistence… when they actually came back to what was there before the invention of RDBMS: a hierarchical semi-structured data model. And now encountering the same problem that the relational database solved 40 years ago. This blog post is about one of those myths.

Index Only access with Oracle, MySQL, PostgreSQL, and Microsoft SQL Server

In my previous post about the advantages of index access over full table scans, I mentioned covering indexes. This is when an Index Range Scan can retrieve all columns without going to the table. Adding to an index all the columns used by the SELECT or WHERE clause is an important tuning technique for queries that are around the inflection point between index access and table full scan. But not all RDBMS are equal. What PostgreSQL calls ‘Index Only’ actually reads the table, except for static data with no concurrent modifications.

I’ll show the execution plans for this Index Only access on Oracle, MySQL, PostgreSQL, and MS SQLServer. As my skills on the non-Oracle ones are very limited, do not hesitate to comment if you think something is not correct.

That demned elusive archive log!

Introduction

With apologies to Emma Orczy again for stealing a line from “The Scarlet Pimpernel” … </p />
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That demned elusive archive log!

Introduction

With apologies to Emma Orczy again for stealing a line from “The Scarlet Pimpernel” … </p />
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Why You Should Periodically Review Your Backups

Introduction

So like every good Oracle DBA, you’ve created a few databases, decided that if they were worth creating and using they might also be worth backing up, and created some backup scripts that do ample logging. All hunky dory, right? You shouldn’t need to revisit this, right?

WRONG!!!

Why You Should Periodically Review Your Backups

Introduction

So like every good Oracle DBA, you’ve created a few databases, decided that if they were worth creating and using they might also be worth backing up, and created some backup scripts that do ample logging. All hunky dory, right? You shouldn’t need to revisit this, right?

WRONG!!!

Creating the Listener and Database in Silent Mode

Introduction

In previous posts, I talked about a customer where I needed to do a silent installation of the Grid Infrastructure and Database, as well as the post installation configuration steps. For that particular customer, I didn’t create an empty database but used RMAN to duplicate the existing database. But what about if you want to create a new listener and database in silent mode as well? That’s what this post covers.