Database (e.g. MySql) :order=>'rand()' is slow.

Solution

Method	Speed	Randomness	Duplicates
1 cluster from random offset	fast	somewhat	no
X times 1 record from random offset	slow for large X	total	possible
n clusters of m record from random offset	fast	good	possible

INSTALL

• As Rails plugin: script/plugin install git://github.com/grosser/random_records.git
• As gem: sudo gem install random_record

USAGE

###Find many in single random cluster (no duplicates) Model.random(1) == [Model(id:322)] Model.random(3) == [Model(id:113),Model(id:112),Model(id:114)] Model.with_valid_email.random(3) == [Model(id:114),Model(id:112),Model(id:113)]

###Find many in many random clusters The smaller the slower (each cluster = 1 request)
May include duplicates so use .uniq on results. Model.random(3, :cluster_size=>1) == [Model(id:112),Model(id:98),Model(id:214)]

###Find one random Model.random == Model(id:234) Model.with_valid_email.random == Model(id:123)

TODO

• prevent duplicates when finding in clusters (searching 9 of 10 -> many requests or tracking which offsets where already fetched)

AUTHOR

Michael Grosser
grosser.michael@gmail.com
Hereby placed under public domain, do what you want, just do not hold me accountable...