Full-Text Search in Django with PostgreSQL PGDay.IT

Originally presented at #PGDay.IT 2017
http://2017.pgday.it/en/schedule/#session-10

Transcript

1. Full-Text Search in Django with PostgreSQL PGDay.IT 2017 - Milan, 2017-10-13  Paolo Melchiorre - @pauloxnet  |
2.  Paolo Melchiorre | ▪Computer Science Engineer ▪Backend Python Developer (>10yrs) ▪Django Developer (~5yrs) ▪Senior Software Engineer @ 20Tab ▪Happy Remote Worker ▪PostgreSQL user, not a DBA 2
3.  Goal | To show how we have used Django Full-Text Search and PostgreSQL in a real project 3
4.  Motivation | To implement Full-Text Search using only Django and PostgreSQL, without resorting to external tools. 4
5.  Agenda | ▪Full-Text Search ▪Existing Solutions ▪PostgreSQL Full-Text Search ▪Django Full-Text Search Support ▪www.concertiaroma.com project ▪What’s next ▪Conclusions ▪Questions 5
6.  Full-Text Search | “… Full-Text Search* refers to techniques for searching a single computer-stored document or a collection in a Full-Text Database …” -- Wikipedia * FTS = Full-Text Search 6
7.  Features of a FTS | ▪Stemming ▪Ranking ▪Stop-words ▪Multiple languages support ▪Accent support ▪Indexing ▪Phrase search 7
8.  Tested Solutions | 8
9.  Elasticsearch | Project: Snap Market (~500.000 mobile users) Issues: ▪Management problems ▪Patching a Java plug-in @@ -52,7 +52,8 @@ public class DecompoundTokenFilter … { - posIncAtt.setPositionIncrement(0); + if (!subwordsonly) + posIncAtt.setPositionIncrement(0); return true; } 9
10.  Apache Solr | Project: GoalScout (~30.000 videos) Issues: ▪Synchronization problems ▪All writes to PostgreSQL and reads from Solr 10
11.  Existing Solutions | PROS  ▪Full featured solutions ▪Resources (documentations, articles, …) CONS  ▪Synchronization ▪Mandatory use of driver (haystack, bungiesearch…) ▪Ops Oriented: focus on system integrations 11
12.  FTS in PostgreSQL | ▪FTS Support since version 8.3 (~2008) ▪TSVECTOR to represent text data ▪TSQUERY to represent search predicates ▪Special Indexes (GIN, GIST) ▪Phrase Search since version 9.6 (~2016) ▪FTS for JSON[b] since version 10 (~2017) 12
13.  What are documents | “… a document is the unit of searching in a Full-Text Search system; for example, a magazine article or email message …” -- PostgreSQL documentation 13
14.  Django Support | ▪Module: django.contrib.postgres ▪FTS Support since version 1.10 (2016) ▪BRIN and GIN indexes since version 1.11 (2017) ▪Dev Oriented: focus on programming 14
15.  Making queries | class Blog(models.Model): name = models.CharField(max_length=100) lang = models.CharField(max_length=100) class Author(models.Model): name = models.CharField(max_length=200) class Entry(models.Model): blog = models.ForeignKey(Blog) headline = models.CharField(max_length=255) body_text = models.TextField() authors = models.ManyToManyField(Author) search_vector = search.SearchVectorField() 15
16.  Standard queries | >>> from blog.models import Author, Blog, Entry >>> Author.objects.filter(name__contains='Terry') SELECT "name" FROM "blog_author" WHERE "name"::text LIKE '%Terry%' ['Terry Gilliam', 'Terry Jones'] >>> Author.objects.filter(name__icontains='Erry') SELECT "name" FROM "blog_author" WHERE UPPER("name"::text) LIKE UPPER('%Erry%') ['Terry Gilliam', 'Terry Jones', 'Jerry Lewis'] 16
17.  Unaccented query | >>> from django.contrib.postgres.operations import ( ... UnaccentExtension) >>> UnaccentExtension() CREATE EXTENSION unaccent; >>> Author.objects.filter(name__unaccent='Helene Joy') SELECT "name" FROM "blog_author" WHERE UNACCENT("name") = (UNACCENT('Helene Joy')) ['Hélène Joy'] 17
18.  Trigram similarity | >>> from django.contrib.postgres.operations import ( ... TrigramExtension) >>> TrigramExtension() CREATE EXTENSION pg_trgm; >>> Author.objects.filter(name__trigram_similar='helena') SELECT "name" FROM "blog_author" WHERE "name" % 'helena' ['Helena Bonham Carter', 'Helen Mirren'] 18
19.  Search lookup | >>> Entry.objects.filter(body_text__search='Cheese') SELECT "headline" FROM "blog_entry" WHERE to_tsvector(COALESCE("body_text", '')) @@ (plainto_tsquery('Cheese')) = true ['Cheese on Toast recipes', 'Pizza Recipes'] >>> from django.contrib.postgres.search import ( ... SearchVector, SearchQuery, SearchRank) 19
20.  SearchVector | >>> vector = SearchVector('body_text', 'blog__name') >>> Entry.objects.annotate(search=vector).filter( ... search='Cheese') SELECT "headline" FROM "blog_entry" INNER JOIN "blog_blog" ON ("blog_id" = "blog_blog"."id") WHERE to_tsvector(COALESCE("body_text", '') || ' ' || COALESCE("name", '')) @@ (plainto_tsquery('Cheese')) = true ['Cheese on Toast recipes', 'Pizza Recipes'] 20
21.  SearchQuery | >>> q = ~SearchQuery('toast') >>> v = SearchVector('body_text') >>> Entry.objects.annotate(search=v).filter(search=q) SELECT "headline" FROM "blog_entry" WHERE to_tsvector(COALESCE("body_text", '')) @@ (!!(plainto_tsquery('toast'))) = true ['Pizza Recipes', 'Pain perdu'] >>> query = SearchQuery('cheese') | SearchQuery('toast') ['Pizza Recipes', 'Cheese on Toast recipes'] >>> query = SearchQuery('cheese') & SearchQuery('toast') ['Cheese on Toast recipes'] 21
22.  SearchRank | >>> vector = SearchVector('body_text') >>> query = SearchQuery('cheese') >>> rank = SearchRank(vector, query) >>> Entry.objects.annotate(rank=rank).order_by('-rank') SELECT "headline", ts_rank( to_tsvector(COALESCE("body_text", '')), plainto_tsquery('cheese')) AS "rank" FROM "blog_entry" ORDER BY "rank" DESC [('Cheese on Toast recipes', 0.0889769), ('Pizza Recipes', 0.0607927), ('Pain perdu', 0.0)] 22
23.  Search confguration | >>> regconfig = 'french' >>> v = SearchVector('body_text', config=regconfig) >>> q = SearchQuery('œuf', config=regconfig) >>> Entry.objects.annotate(search=v).filter(search=q) SELECT "headline" FROM "blog_entry" WHERE to_tsvector( 'french'::regconfig, COALESCE("body_text", '')) @@ (plainto_tsquery('french'::regconfig, 'œuf')) = true ['Pain perdu'] >>> from django.db.models import F >>> regconfig = F('blog__lang') 23
24.  Queries weighting | >>> vector = SearchVector('body_text', weight='A') + ... SearchVector('headline', weight='B') >>> query = SearchQuery('cheese') >>> rank = SearchRank(vector, query) >>> Entry.objects.annotate(rank=rank).order_by('rank') SELECT "headline", ts_rank(( setweight(to_tsvector(COALESCE("body_text", '')), 'A') || setweight(to_tsvector(COALESCE("headline", '')), 'B')), plainto_tsquery('cheese')) AS "rank" FROM "blog_entry" ORDER BY "rank" DESC [('Cheese on Toast recipes', 0.896524), ('Pizza Recipes', 0.607927), ('Pain perdu', 0.0)] 24
25.  SearchVectorField | >>> vector = SearchVector('body_text') >>> Entry.objects.update(search_vector=vector) UPDATE "blog_entry" SET "search_vector" = to_tsvector(COALESCE("body_text", '')) >>> Entry.objects.filter(search_vector='cheese') SELECT "headline" FROM "blog_entry" WHERE "search_vector" @@ (plainto_tsquery('cheese')) = true ['Cheese on Toast recipes', 'Pizza Recipes'] 25
26.  www.concertiaroma.com| “… today's shows in the Capital” * The numbers of the project: ~ 1.000 venues > 13.000 bands > 16.000 shows ~ 200 festivals ~ 30.000 user/month * since 2014 26
27.  Version 2.0 | Python 2.7 - Django 1.7 - PostgreSQL 9.1 - SQL LIKE 27
28.  Version 3.0 | Python 3.6 - Django 1.11 - PostgreSQL 9.6 - PG FTS 28
29.  Band models | class Genre(models.Model): name = models.CharField(max_length=255) class Band(models.Model): nickname = models.CharField(max_length=255) description = models.TextField() genres = models.ManyToManyField(Genre) objects = BandManager() class Meta: indexes = [GinIndex(fields=['search_vector'])] 29
30.  Band Manager | SEARCH_VECTORS = ( SearchVector('nickname', weight='A', config='usimple') + SearchVector('genres__name', weight='B', config='usimple') + SearchVector('description', weight='D', config='usimple')) class BandManager(models.Manager): def search(self, text): query = SearchQuery(text, config='usimple') rate = SearchRank(SEARCH_VECTORS, query) similarity = TrigramSimilarity('nickname', text) return self.get_queryset().annotate( search=vector).filter(search=query).annotate( rate=rate + similarity).order_by('-rate') 30
31.  Band Test Setup | class BandTest(TestCase): def setUp(self): metal, _ = Genre.objects.get_or_create(name='Metal') doom, _ = Genre.objects.get_or_create(name='Doom') doomraiser, _ = Band.objects.get_or_create( nickname='Doom raiser', description='Lorem…') doomraiser.genres.add(doom) forgotten_tomb, _ = Band.objects.get_or_create( nickname='Forgotten Tomb', description='Lorem…') forgotten_tomb.genres.add(doom) ... 31
32.  Band Test Method | class BandTest(TestCase): ... def test_band_search(self): band_queryset = Band.objects.search( 'doom').values_list('nickname', 'rate') band_list = [ ('Doom raiser', 0.675475), ('The Foreshadowin', 0.258369), ('Forgotten Tomb', 0.243171)] self.assertSequenceEqual( list(OrderedDict(band_queryset).items()), band_list) 32
33.  What’s next | ▪Advanced Misspelling support ▪Multiple language configuration ▪Search suggestions ▪SearchVectorField with triggers ▪JSON/JSONB Full-Text Search ▪RUM indexing 33
34.  Conclusions | Conditions to implement this solution: ▪No extra dependencies ▪Not too complex searches ▪Easy management ▪No need to synchronize data ▪PostgreSQL already in your stack ▪Python-only environment 34
35.  Acknowledgements | Marc Tamlyn for all the Support for django.contrib.postgres www.20tab.com github.com/mjtamlyn 36
36.  Resources | ▪postgresql.org/docs/9.6/static/textsearch.html ▪github.com/damoti/django-tsvector-field ▪en.wikipedia.org/wiki/Full-text_search ▪docs.djangoproject.com/en/1.11/ref/contrib/postgres ▪stackoverflow.com/.../django+postgresql+full-text... ▪simonwillison.net/.../django-postgresql-faceted-search ▪PostgreSQL & Django source code 35
37.  Thank you |   BY -  SA (Attribution-ShareAlike) creativecommons.org/licenses/by-sa  Source Code github.com/pauloxnet/django_queries  Slides speakerdeck.com/pauloxnet 37
38.  Questions ? |  38
39.  Contacts |  www.paulox.net  twitter.com/pauloxnet  linkedin.com/in/paolomelchiorre  github.com/pauloxnet 39