Real time fulltext search with sphinx


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My talk about real-time indexing and searching with Sphinx. It was given at the 2013 Froscon in Sankt Augustin, Germany.

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Real time fulltext search with sphinx

  1. 1. Real time fulltext search with Sphinx Adrian Nuta // Sphinxsearch // 2013
  2. 2. Quick intro Sphinx search • high performance fulltext search engine • written in C++ • serving searches since 2001 • can work on any modern architecture • distributed under GPL2 licence
  3. 3. Why a search engine? • performance o a search engine delivery faster a search and with less resourses • quality of search o build-in FTS in databases don’t offer advanced search options • independent FTS engines offer speed not only for FT searches, but other types, like geo or faceted searches
  4. 4. Classic way of indexing in Sphinx on-disk (classic) method: • use a data source which is indexed • to update the index you need to reindex again • in addition to main index, a secondary index (delta) index can be used to reindex only latest changes • easy because indexing doesn’t require changes in the application, but: • reindexing, even delta one, can put pressure on data source and system
  5. 5. Real time indexing in Sphinx • index has no data source • everything that needs be indexed must be added manually in the index • you can add/update/remove at any time • compared to classic method, RT requires changes in the application • performance is same or near same as classic index • Only specific requirement : workers = threads
  6. 6. Structures
  7. 7. RealTime index definition index rt { type = rt rt_field = title rt_field = content rt_attr_uint = user_id rt_attr_string = title rt_attr_json = metadata }
  8. 8. Schema - Fields rt_field - fulltext field, raw text is not stored Tokenization features: wildcarding ( prefix or infix), morphology, custom charset definition, stopwords, synonyms, segmentation, html stripping, paragraph/sentence detection etc.
  9. 9. Schema - Attributes • rt_attr_uint & rt_attr_bigint • rt_attr_bool • rt_attr_float • rt_attr_multi & rt_attr_multi64 - integer set • rt_attr_timestamp • rt_attr_string - actual text stored, kept in memory, used only for display, sorting and grouping. • rt_attr_json - full support for JSON documents
  10. 10. Content manipulation
  11. 11. Quick intro to SphinxQL • our SQL dialect • any mysql client can be used to connect to Sphinx • MySQL server is not required! • Full document updates only possible with SphinxQL • to enable it, add in searchd section of config listen = host:port:mysql41
  12. 12. Content insert $mysql> INSERT INTO rt (id,title,content,user_id,metadata) VALUES(100,’My title’, ‘Some long content to search’, 10, ’{“image_id”:1,”props”:[20,30,40]}’);
  13. 13. Full content replace $mysql> REPLACE INTO rt (id,title,content,user_id,metadata) VALUES(100,’My title’, ‘Some long content to search’, 10, ’{“image_id”:1,”props”:[20,30,40]}’); • needed for text field, json and string attribute updates
  14. 14. Updating numerics • For numeric attributes including MVA: $mysql> UPDATE rt SET user_id = 10 WHERE id = 100; • For numeric JSON elements it’s possible to do inplace updates: $mysql> UPDATE rt SET metadata.image_id = 1234 WHERE id=100;
  15. 15. Deleting $mysql> DELETE FROM rt WHERE id = 100; $mysql> DELETE FROM rt WHERE user_id > 100; $mysql> TRUNCATE RTINDEX rt; ● empty the memory shard, delete all disk shards and release the index binlogs
  16. 16. Adding new attributes mysql> ALTER TABLE rt ADD COLUMN gid INTEGER; • only for int/bigint/float/bool attributes for now
  17. 17. Searching
  18. 18. Searching • no difference in searching a RT or classic index • dict = keywords required for wildcard search.
  19. 19. Relevancy ranking • build-in rankers: o proximity_bm25 ( default) o none, matchany,wordcount,fieldmask,bm25 • custom ranker - create own expression rank example ranker = proximity_bm25 same as ranker = expr(‘sum(lcs*user_weight)*1000+bm25’)
  20. 20. Tokenization settings example index rt { … charset_type = utf-8 dict = keywords min_word_len = 2 min_infix_len = 3 morphology = stem_en enable_star = 1 … }
  21. 21. Operators on fulltext fields • Boolean: hello | world, hello ! world • phrasing: “hello world” • proximity: “hello world”~10 • quorum: “world is a beautiful place”/3 • exact form: =cats and =dogs • strict order: cats << and << dogs • zone limit: (h2,h4) cats and dogs • SENTENCE: all SENTENCE words SENTENCE “ in one sentence” • PARAGRAPH: “this search” PARAGRAPH “is fast” • selected fields only: @(title,body) hello world • excluded fields: @!(title,body) hello world
  22. 22. Using API <?php require("sphinxapi.php"); $cl = new SphinxClient(); $res = $cl->Query('search me now','rt'); print_r($res); Official: PHP, Python, Ruby, Java, C Unofficial: JS(Node.js), perl, C++, Haskell, .NET
  23. 23. Using SphinxQL $mysql> SELECT * FROM rt WHERE MATCH('”search me fuzzy”~10') AND featured = 1 LIMIT 0,20; $mysql> SELECT * FROM rt WHERE MATCH('”search me fuzzy”~10 @tag computers') AND featured = 1 GROUP BY user_id ORDER BY title ASC LIMIT 30,60 OPTION field_weights=(title=10,content=1), ranker=expr(‘sum((4*lcs+2*(min_hit_pos==1) +exact_hit)*user_weight)*1000+bm25’);
  24. 24. Boolean filtering $mysql> SELECT *, views > 10 OR category = 4 AS cond FROM rt WHERE MATCH('”search me proximity”~10') AND featured = 1 AND cond = 1 GROUP BY user_id ORDER BY title ASC LIMIT 30,60 OPTION ranker=sph04;
  25. 25. Geo search mysql> SELECT *, GEODIST(lat,long,0.71147,- 1.29153) as distance FROM rt WHERE distance < 1000 ORDER BY distance ASC; mysql> SELECT *, GEODIST(lat,long,40.76439,- 73.99976, {in=degrees,out=miles,method=adaptive}) as distance FROM rt WHERE distance < 10 ORDER BY distance ASC;
  26. 26. Multi-queries mysql> DELIMITER mysql> SELECT *,COUNT(*) as counter FROM rt WHERE MATCH('search me') GROUP by property_one ORDER by counter DESC;SELECT *,COUNT(*) as counter FROM rt WHERE MATCH('search me') GROUP by property_two ORDER by counter DESC;SELECT *,COUNT(*) as counter FROM rt WHERE MATCH('search me') GROUP by property_three ORDER by counter DESC; • used for faceting
  27. 27. Internals
  28. 28. Internal architecture Each RT index is a sharded index consisting of: • one memory shard for latest content • one or more disk shards
  29. 29. Internal shards management rt_mem_limit = maximum size of memory shard When full, is flushed to disk as a new disk shard. • OPTIMIZE INDEX rt - merge all disk shards into one. o Merging too intensive? throttle with rt_merge_iops and rt_merge_maxiosize
  30. 30. Binlog support Sphinx support binlogs, so memory shard will not be lost in case of disasters • binlog_flush o like innodb_flush_log_at_trx_commit o 0 - flush and sync every second - fastest, 1 sec lose o 1 - flush and sync every transaction - most safe, but slowest o 2 - flush every transaction, sync every second - best balance, default mode • binlog_path o binlog_path = # disable logging
  31. 31. Fast RT setup using classic index • Create classic index to get initial data. • Declare a RT index • mysql> ATTACH INDEX classic TO RTINDEX rt • transform classic index to RT • operation is almost instant o in essence is a file renaming: classic index becomes a RT disk shard
  32. 32. Sphinx use 1 CPU core per index More power? Distribute!
  33. 33. Distributed RT index Update on each shard, search on everything index distributed { type = distributed local = rtlocal_one local = rtlocal_two agent = some.ip:rtremote_one } don’t forget about dist_threads = x
  34. 34. Copy RT index from one server to another • just simulate a daemon restart • searchd --stopwait • flushes memory shard to disk • Copy all index files to new server. • Add RT index on new server sphinx.conf • Start searchd on new server
  35. 35. Questions? Docs: Wiki: Official blog: SVN repository:
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