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Couchbase Server 2.0 - Indexing and Querying - Deep dive

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Deep dive presentation on Indexing and Querying - new to Couchbase Server 2.0

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Couchbase Server 2.0 - Indexing and Querying - Deep dive

  1. 1. Couchbase Server 2.0 Indexing and Querying Quick Overview Dipti Borkar Director, Product Management 1 1
  2. 2. What we’ll talk about • View basics • Lifecycle of a view  Index definition, build, and query phase  Indexing details • Replica indexes, failover and compaction • Primary and Secondary indexes • View best practices • Additional patterns 2
  3. 3. JSON Documents• Map more closely to objects or entities• CRUD Operations, lightweight schema { “fields” : [“with basic types”, 3.14159, true], “like” : “your favorite language” }• Stored under an identifier key client.set(“mydocumentid”, myDocument); mySavedDocument = client.get(“mydocumentid”); 3
  4. 4. What are Views? • Extract fields from JSON documents and produce an index of the selected information
  5. 5. Views – The basics• Define materialized views on JSON documents and then query across the data set• Using views you can define • Primary indexes • Simple secondary indexes (most common use case) • Complex secondary, tertiary and composite indexes • Aggregations (reduction)• Indexes are eventually indexed• Queries are eventually consistent with respect to documents• Built using Map/Reduce technology • Map and Reduce functions are written in Javascript
  6. 6. View LifecycleDefine -> Build -> Query 66
  7. 7. Buckets & Design docs & Views• Create design documents on a bucket• Create views within a design document BUCKET 1 View 11 View Design  document 1 View 22 View View 33 View Design View 44 View  document 2 View 55 View Design View 66 View  document 3 View 77 View BUCKET 2 7
  8. 8. Eventually indexed Views – Data flow 2 Doc 1 App Server Couchbase Server Node 33 2 33 Managed Cache 2 To other node Replication Doc 1 Queue Disk Queue Disk Doc 1 View engine 8
  9. 9. Distributed Indexing and Querying Create Index / View App Server 1 App Server 2 COUCHBASE Client Library COUCHBASE Client Library COUCHBASE Client Library COUCHBASE Client Library Cluster Map Cluster Map Query Server 1 Server 2 Server 3 • Indexing work is distributed Active Active Active amongst nodes Doc 5 Doc Doc 3 Doc Doc 4 Doc • Parallelize the effort Doc 2 Doc Doc 1 Doc Doc 6 Doc • Each node has index for data stored Doc 9 Doc Doc 8 Doc Doc 7 Doc on it REPLICA • Queries combine the results from REPLICA REPLICA required nodes Doc 3 Doc Doc 6 Doc Doc 2 Doc Doc 1 Doc Doc 4 Doc Doc 5 Doc Doc 7 Doc Doc 9 Doc Doc 8 Doc Couchbase Server ClusterUser Configured Replica Count = 1 9
  10. 10. DEFINE  Index / View Definition in JavaScript CREATE INDEX City ON Brewery.City; 10
  11. 11. BUILD  Distributed Index Build Phase• Optimized for lookups, in-order access and aggregations• View reads are from disk (different performance profile than GET/SET)• Views built against every document on every node – Group them in a design document• Views are automatically kept up to date 11
  12. 12. QUERY  Dynamic Queries with Optional Aggregation• Eventually consistent with respect to document updates• Efficiently fetch a document or group of similar documents• Queries will use cached values from B-tree inner nodes when possible• Take advantage of in-order tree traversal with group_level queries Query ?startkey=“J”&endkey=“K” {“rows”:[{“key”:“Juneau”,“value”:null}]} 12
  13. 13. Index building details – All the views within a design document are incrementally updated when the view is accessed or auto-indexing kicks in – Automatic view updates • In addition to forcing an index build at query time, active & replica indexes are updated every 3 seconds of inactivity if there are at least 5000 new changes (configurable) – The entire view is recreated if the view definition has changed – Views can be conditionally updated by specifying the “stale” argument to the view query – The index information stored on disk consists of the combination of both the key and value information defined within your view.
  14. 14. Queries run against stale indexes by default• stale=update_after (default if nothing is specified) – always get fastest response – can take two queries to read your own writes• stale=ok – auto update will trigger eventually – might not see your own writes for a few minutes – least frequent updates -> least resource impact• stale=false – Use with “set with persistence” if data needs to be included in view results – BUT be aware of delay it adds, only use when really required 14
  15. 15. Views and Replica indexes• In addition to replicas for data (up to 3 copies), optionally create replica for indexes• Each node manages replica index data structures• Set at a bucket level• Replica index populated from replica data• Replica index is used after a failover
  16. 16. Views and failover• Replica indexes enabled on failover• Replicas indexes are rebuilt on replica nodes – Automatically incrementally built based on replica data – Updated every 3 seconds of inactivity if there are at least 5000 new changes – Not copied/moved to be consistent with persisted replica data
  17. 17. View Compaction • Compaction is ONLINE • Reclaims empty allocated space from disk • Indexes are stored on disk for active vBuckets on each node and updated in append-only manner • Auto-compaction performed in the background – Set the database fragmentation levels – Set the index fragmentation levels – Choose a schedule – Global and bucket specific settings
  18. 18. Development vs. Production Views• Development views index a subset of the data.• Publishing a view builds the index across the entire cluster.• Queries on production views are scattered to all cluster members and results are gathered and returned to the client. 18
  19. 19. Simple Primary andSecondary Indexing 19 1
  20. 20. Example Document Document ID 20
  21. 21. Define a primary index on the bucket• Lookup the document ID / key by key, range, prefix, suffix Index definition 21
  22. 22. Define a secondary index on the bucket• Lookup an attribute by value, range, prefix, suffix Index definition 22
  23. 23. Find documents by a specific attribute• Lets find beers by brewery_id! 23
  24. 24. The index definition Key Value 24
  25. 25. The result set: beers keyed by brewery_id 25
  26. 26. View Best Practices 26 2
  27. 27. View writing guidance• Move frequently used views out to a separate design document – All views in a design document are updated at the same time – This can result in increase index building time if all views are in a single design document, especially for frequently accessed views. – However, grouping views into smaller number of design documents improves overall performance• Try to avoid computing too many things with one view• Use built-in reduces where possible - custom reduces are not optimized• Check for attribute existence function(doc, meta){ function(doc, meta){ if (doc.ingredient) if (doc.ingredient) { { emit(doc.ingredient.ingredtext, null); emit(doc.ingredient.ingredtext, null); } } } } 27
  28. 28. View writing guidance• Do not include the document in the view value – Instead either use the GET / SET API or the API that includes documents filtered by the query [example: willIncludeDocs()] – Emit either null or the ID instead (meta.id) in your key or value data emit(doc.name, null) emit(doc.name, null)• Don’t emit too much data into a view value – Use views to filter documents – Then use the data path to access the matched documents• Use Document Types to make views more selective function(doc, meta) function(doc, meta) { { if(doc.type == “player”) if(doc.type == “player”) emit(doc.experience, null); emit(doc.experience, null); } } 28
  29. 29. What impact do views have on the system?• Complexity of the index  CPU• Size of the value emitted and selectivity  Disk size, I/O• Replica index  Disk size, I/O, CPU• Number of design doc  CPU, I/O, Disk size – 4 active and 2 replica design documents are built in parallel by default – Can be changed using the maxParallelIndexers and maxParallelReplicaIndexers parameters• Compaction of views  CPU, I/O• Rebalance time Increases with views to support consistent query results during rebalance – Can be disabled using the indexAwareRebalanceDisabled parameter
  30. 30. Views and OS caching• File system cache availability for the index has a big impact performance• Indexes are disk based and should have sufficient file system cache available for faster query access• In house performance results show that by doubling system cache availability – query latency reduces to half – throughput increases by 50%• Runs based on 10 million items with 16GB bucket quota and 4GB, 8GB system RAM availability for indexes
  31. 31. Query PatternBasic Aggregations 31 3
  32. 32. Use a built-in reduce function with a group query• Lets find average abv for each brewery! 32
  33. 33. We are reducing doc.abv with _stats 33 33
  34. 34. Group reduce (reduce by unique key) 34 34
  35. 35. Query PatternTime-based Rollups 35 3
  36. 36. Find patterns in beer comments by time { "type": "comment", "about_id": "beer_Enlightened_Black_Ale", "user_id": 525, timestamp "text": "tastes like college!", "updated": "2010-07-22 20:00:20" { } "id": "f1e62" } 36
  37. 37. Query with group_level=2 to get monthly rollups 37
  38. 38. dateToArray() is your friend () rr ay oA eT dat• String or Integer based timestamps• Output optimized for group_level queries• array of JSON numbers: [2012,9,21,11,30,44] 38
  39. 39. group_level=2 results• Monthly rollup• Sorted by time—sort the query results in your application if you want to rank by value—no chained map-reduce 39
  40. 40. group_level=3 - daily results - great for graphing• Daily, hourly, minute or second rollup all possible with the same index. 40
  41. 41. Query Pattern Leaderboard 41 4
  42. 42. Aggregate value stored in a document• Lets find the top-rated beers! { "brewery": "New Belgium Brewing", "name": "1554 Enlightened Black Ale", "abv": 5.5, "description": "Born of a flood...", "category": "Belgian and French Ale", "style": "Other Belgian-Style Ales", "updated": "2010-07-22 20:00:20", “ratings” : { ratings “jchris” : 5, “scalabl3” : 4, “damienkatz” : 1 42
  43. 43. Sort each beer by its average rating• Lets find the top-rated beers! average 43 43
  44. 44. Questions? 44 4