WiredTiger and growing documents

[Alex Sergeyev]

Hi, 

My current pattern for mongodb usage is to store timeseries with one minute resolution in one document per day.  To avoid document relocation for mongo < 3.0 I need to pad each document on creation with nil values for all timestamps for this day. How WiredTiger will work with growing documents? Do I need also to pad empty values or can just add values to same document?

[MARK CALLAGHAN]

The WiredTiger b-tree is copy-on-write so it isn't constrained by a
fixed page size. I assume that means there is less concern about
growing or shrinking documents and no need for client-side padding.
But this is one more question for the WT experts to answer in the
pending WT performance guide.

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[Stephen Steneker]

On Friday, 27 February 2015 08:36:15 UTC+11, Alex Sergeyev wrote:

My current pattern for mongodb usage is to store timeseries with one minute resolution in one document per day.  To avoid document relocation for mongo < 3.0 I need to pad each document on creation with nil values for all timestamps for this day. How WiredTiger will work with growing documents? Do I need also to pad empty values or can just add values to same document?

Hi Alex,

WiredTiger doesn't do in-place updates; padding is only applicable to mmap storage. You'll want to remove any manual padding if you change to WiredTiger, and just add/update values as required.

As with any major database upgrade, I would encourage you to thoroughly test to see how the performance differs for your use case.

Regards,

Stephen