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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Comparison page for RavenDB and MongoDB

Feb 16 2006

Circular Dependencies

time to read 2 min | 266 words

So, I need to copy a set of tables from one database to another, the issue is that the source database keeps changing, so, in a true developer fashion, I added another layer of indirection and instead of writing scripts to copy the database I wrote a program that would write scripts that would copy the database.

I'm pretty proud of it, it uses the SQL Runner tool that I mentioned earlier, and it work in stages, so the first thing that copied is tables with no foreign keys, then the tables that depended on those, and then the tables that depend on those, and so on. The issue is that I've a couple of tables that have circular dependencies (sometimes a dependency on itself). This presents an interesting problem since I don't want to start special casing for each table type.

I can see several options there:

Drop the foreign keys, copy the tables and recreate from scratch - On general I don't like this, especially since generating the code to recreate the foreign key is not trivial.
Try to copy anyway, maybe I would get lucky or there aren't any real references between the tables.
Leave it as a totally manual process (which is a real option, since this is a mostly one off thing).

Ideas?

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FUTURE POSTS

NTFS has an emergency stash of disk space - one day from now
Challenge: Giving file system developer ulcer - 4 days from now
RavenDB 7.1: Next-Gen Pagers - 11 days from now
RavenDB 7.1: Write modes - 13 days from now
RavenDB 7.1: Reclaiming disk space - 15 days from now

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RECENT COMMENTS

Dmitry, Yes, but this is _known_ to be a 64 bits system - since we are allocating 3GB (not possible in 64 bits). Note t...

By Oren Eini on Answer: What does this code do?
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...

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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.

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It could be interesting to reach out to storage firmware developers and ask what write patterns they think would be useful ex...

By kpvleeuwen on Performance discovery: IOPS vs. IOPS

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