NoSql Introduction

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NoSQL presentation at Locaweb/Brazil.
Basic ideas, anti-patterns and some ideas of when/how to jump to NoSQL solutions.

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NoSql Introduction

  1. 1. NoSQL Brief intro Gleicon Moraes
  2. 2. Doing it wrong, Junior !
  3. 3. SQL Anti patterns and related stuff The eternal tree (rows refer to the table itself - think threaded discussion) Dynamic table creation (and dynamic query building) Table as cache (lets save it in another table) Table as queue (wtf) Extreme JOINs (app requires a warmed up cache) Your scheme must be printed in an A3 sheet. Your ORM issue full queries for Dataset iterations
  4. 4. The eternal tree Problem: Most threaded discussion example uses something like a table which contains all threads and answers, relating to each other by an id. Usually the developer will come up with his own binary-tree version to manage this mess. id - parent_id -author - text 1 - 0 - gleicon - hello world 2 - 1 - elvis - shout ! NoSQL alternative: Document storage: { thread_id:1, title: 'the meeting', author: 'gleicon', replies:[ { 'author': elvis, text:'shout', replies:[{...}] } ] }
  5. 5. Dynamic table creation Problem: To avoid huge tables, one must come with a "dynamic schema". For example, lets think about a document management company, which is adding new facilities over the country. For each storage facility, a new table is created: item_id - row - column - stuff 1 - 10 - 20 - cat food 2 - 12 - 32 - trout Now you have to come up with "dynamic queries", which will probably query a "central storage" table and issue a huge join to check if you have enough cat food over the country. NoSQL alternative: - Document storage, modeling a facility as a document - Key/Value, modeling each facility as a SET
  6. 6. Table as cache Problem: Complex queries demand that a result be stored in a separated table, so it can be queried quickly. NoSQL alternative: - Really ? - Memcached - Redis (for persistence) - Denormalization
  7. 7. Table as queue Problem: A table which holds messages to be completed. Worse, they must be ordered. NoSQL alternative: - RestMQ - Any other message broker - Redis (for LISTS) - Use the right tool
  8. 8. Extreme JOINs Problem: Business stuff modeled as tables. Table inheritance (Product -> SubProduct_A). To find the complete data for a user plan, one must issue gigantic queries with lots of JOINs. NoSQL alternative: - Document storage, as MongoDB - Denormalization
  9. 9. Your scheme fits in an A3 sheet Problem: Huge data schemes are difficult to manage. Extreme specialization creates tables which converges to key/value model. The normal form get priority over common sense. Product_A Product_B id - desc id - desc NoSQL alternative: - Denormalization - Another scheme ? - Document store - Key/Value
  10. 10. Your ORM ... Problem: Your ORM issue full queries for dataset iterations, your ORM maps and creates tables which mimics your classes, even the inheritance, and the performance is bad because the queries are huge, etc, etc NoSQL alternative: Apart from denormalization and good old common sense, ORMs are trying to bridge two things with distinct impedance. There is nothing to relational models which maps cleanly to classes and objects. Not even the basic unit which is the domain(set) of each column. Black Magic ?
  11. 11. No silver bullet - Consider alternatives - Think outside the norm - Denormalize - Simplify
  12. 12. Cycle of changes - Product A 1. There was the database model 2. Then, the cache was needed. Performance was no good. 3. Cache key: query, value: resultset 4. High or inexistent expiration time [w00t] (Now there's a turning point. Data didn't need to change often. Denormalization was a given with cache) 5. The cache needs to be warmed or the app wont work. 6. Key/Value storage was a natural choice. No data on MySQL anymore.
  13. 13. Cycle of changes - Product B 1. Postgres DB storing crawler results. 2. There was a counter in each row, and updating this counter caused contention errors. 3. Memcache for reads. Performance is better. 4. First MongoDB test, no more deadlocks from counter update. 5. Data model was simplified, the entire crawled doc was stored.
  14. 14. Stuff to think about Think if the data you use aren't denormalized (cached) Most of the anti-patterns contain signs that the NoSQL route (or at least a partial NoSQL route) may simplify. Are you dependent on cache ? Does your application fails when there is no cache ? Does it just slows down ? Are you ready to think more about your data ? Think about the way to put and to get back your data from the database (be it SQL or NoSQL).

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