Friday Apr 24, 2015

In-Memory Priority

I'd like to thank everyone who attended our two Hands On Lab sessions at Collaborate last week. We had a great time presenting them and we received some really good feedback. One of the questions that came up, and gets asked periodically, is how does In-Memory priority really work?

Many times people have the misconception that the In-Memory priority attribute affects more than just the order of population but that’s not the case. The only thing the priority affects is the order of population at database startup. We discussed population briefly some time ago, but I think it's worth a quick review.

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Friday Apr 17, 2015

CPU Efficient Query Processing with Database In-Memory

In my last post I talked about In-Memory Aggregation and mentioned that the vector transformation plan is more CPU efficient than alternative plans. In this post I’ll provide a few examples to illustrate just how effective a vector transformation plan can be.

Let’s consider a star schema, with one fact table and 9 dimension tables (time, customer, product, channel and demographic attributes such as age and income).

9 Dimensional Star

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Thursday Apr 09, 2015

Push-Down: Part 2

In our previous post we introduced the concept of push down. The ability to push predicates, aggregations and group-bys down into the scan of a column or columns, allowing Oracle to take full advantage of all the scan performance features of the In-Memory column store. We also illustrated how you could monitor the benefits of push down via session level statistics (v$mystat). What you might not have realized is that we can also see what where clause predicates get push via the execution plan.

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Tuesday Mar 31, 2015

Push-Down: Making Queries Fast!

In our previous posts we discussed the basic architecture of the In-Memory column store (IM column store) and now we want to drill down into some of the unique performance enhancing features. Push-down is one of the optimizations that makes scanning columns in the IM column store very efficient. Oracle Database In-Memory has the ability to push predicates, aggregations and group-bys down into the scan of a column or columns.  This ability to push-down allows us to take advantage of other performance enhancing features of Database In-Memory like SIMD vector processing and storage indexes.

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Monday Jul 14, 2014

In-Memory Column Store versus the Buffer Cache

In this week's blog post I'm going to address just one question. It's actually the question I have gotten the most since I started blogging on Oracle Database In-Memory.

Why does In-Memory populate complete tables or partitions into memory instead of caching frequently accessed blocks like the buffer cache?

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The Oracle Database In-Memory blog is written by the Oracle product management team and sheds light on all things In-Memory.

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