Create Tags for an Object and Search for Tags
Credit: Gleicon Moraes
Problem
You want tags for your objects, and want to be able to search them.
Solution
In this case, using books as an example, create one SET for each tag, and associate the given ids to the correct sets. Selecting a combination between tags is simple as using SINTER, SUNION and SDIFF. The same principle can be used for document storage, taking care to use words or its stems as 'tags'
In redis-cli:
SET book:1 {'title' : 'Diving into Python',
'author': 'Mark Pilgrim'}
SET book:2 { 'title' : 'Programing Erlang',
'author': 'Joe Armstrong'}
SET book:3 { 'title' : 'Programing in Haskell',
'author': 'Graham Hutton'}
SADD tag:python 1
SADD tag:erlang 2
SADD tag:haskell 3
SADD tag:programming 1 2 3
SADD tag computing 1 2 3
SADD tag:distributedcomputing 2
SADD tag:FP 2 3
Now, the searching/selecting part:
a) SINTER 'tag:erlang' 'tag:haskell'
0 results
b) SINTER 'tag:programming' 'tag:computing'
3 results: 1, 2, 3
c) SUNION 'tag:erlang' 'tag:haskell'
2 results: 2 and 3
d) SDIFF 'tag:programming' 'tag:haskell'
2 results: 1 and 2 (haskell is excluded)
Discussion
SETs and ZSETs operations are building blocks for basic and advanced combinations which yields more results per search.
- In (a), there is no book tagged erlang AND haskell.
- In (b) is the same as searching for ALL BOOKS tagged programming and computing
- BOOKS that are tagged either erlang or haskell are found on (c)
- (d) excludes all books tagged haskell from the programming group.
For a document based storage and search, check meta code at http://github.com/gleicon/docdb. It may look overkill, but after some documents, the number of sets doesnt grow that much.