[patch] sm -s -R and overview mechanisms

Julien ÉLIE julien at trigofacile.com
Mon Nov 23 12:08:29 UTC 2020

Hi Bo,
> One build-and-install later, a size comparison becomes possible:
>> -rwxr-xr-x  1 root  wheel  1700816 Nov 23 09:49 /usr/local/BerkeleyDB.18.1/lib/libdb-18.1.dylib
>> -rwxr-xr-x  1 root  wheel  1735808 Oct 13 10:04 /usr/local/lib/libsqlite3.0.dylib
> Code size is not a strong argument against SQLite.

Was it at the time Berkeley DB choice for INN was made?

I'm also wondering what the pros are for a DBMS like SQLite or Berkeley 
DB.  For a new user, INSTALL does not necessarily help to choose.  Do 
you see any thoughts that should be added?

For a full-text feed nowadays, on modern hardware, would we see a real 
difference between the 3 mechanisms in termes of speed or maximum number 
of users at the same time?
Has anyone had a chance to benchmark the 3 of them?

Quoting INSTALL:

There are three overview mechanisms to choose from:

It is very fast for readers, but it has to update two files for each 
incoming article and can be quite slow to write.

It can keep up with a large feed more easily, since it uses large 
buffers to store all overview information, but it's somewhat slower for 
readers (although not as slow as the unified overview in INN 2.2).  You 
will need to create the buffers for it to use (very similar to creating 
CNFS buffers) and list the available buffers in buffindexed.conf.

It stores overview data in a Berkeley DB database; it's fast and very 
robust, but may require more disk space.

And according to ovdb documentation:

The ovdb database may take up more disk space for a given spool than the 
other overview methods.  Plan on needing at least 1.1 KB for every 
article in your spool (not counting crossposts).  So, if you have 5 
million articles, you'll need at least 5.5 GB of disk space for ovdb. 
With compression enabled, this estimate changes to 0.7 KB per article. 
Plus, you'll need additional space for transaction logs: at least 100 MB.

Julien ÉLIE

« Pourquoi apprendre à calculer la surface d'un losange ? Au cours de ma
   vie, je n'ai jamais compté aucun losange parmi mes relations. »
   (Jacques Sternberg)

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