Oren Eini

aka Ayende Rahien

Oren Eini

CEO of RavenDB

a NoSQL Open Source Document Database

Get in touch with me:

oren@ravendb.net

+972 52-548-6969

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RavenDB Workshops - Deep dive into practical use of Document Data Modeling

Oct 19 2006

The cost of eager load...

time to read 1 min | 188 words

This is the profiler results from trying to understand why I got very slow responses from the server...

(Image from clipboard).png

Notice what is costing so much time here. The first issue was that the system was generated huge amounts of queries, and the quick & dirty solution was to throw caching on top of this, which had a difference of three to five orders of magnitude. The image above is after applying the caching, by the way, and there is no database activity in this call graph.

But performance continue to suffer, and I wasn't quite sure why. A quick look at the profiler and then at the mapping showed the reason quite clearly. In this case, the issue is a God Class (you know those, the one that is connected to all the entities in the database) that has no lazy collections.

As a result of this, per request, NHibernate had to construct the entire database in memory. Often just because the developer wanted to display a single (simple) property from the God Class.

When I removed the access to this class, I got about 10x performance boost...

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RECENT COMMENTS

That's why it is a good idea to compare the return value of `write` to the buffer size. "size_t" can be 32-bit on some system...

By Dmitry on Answer: What does this code do?
There's a reason we miss `write_exact` and `read_exact` from the standard library. In fact, I am surprised the chunk is actua...

By Pyth0n on Challenge: What does this code do?
kpvleeuwen, I agree, unfortunately I don't have anyone to ask off the top of my head. Thanks, I fixed the headers.

By Oren Eini on Performance discovery: IOPS vs. IOPS
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Nicholas, You _can_ use the spread operator in RavenDB, which is what I assume you meant, like this: let results = ...

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