483 lines
18 KiB
Python
483 lines
18 KiB
Python
"""Search backends used by django-watson."""
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from __future__ import unicode_literals
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import abc
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import re
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from django.conf import settings
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from django.contrib.contenttypes.models import ContentType
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from django.db import transaction, connections, router
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from django.db.models import Q
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from django.utils.encoding import force_text
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from django.utils import six
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from watson.models import SearchEntry, has_int_pk
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def regex_from_word(word):
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"""Generates a regext from the given search word."""
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return "(\s{word})|(^{word})".format(
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word=re.escape(word),
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)
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# PostgreSQL to_tsquery operators: ! & : ( ) |
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RE_POSTGRES_ESCAPE_CHARS = re.compile(r'[&:(|)!><]', re.UNICODE)
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# MySQL boolean full-text search operators: > < ( ) " ~ * + -
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RE_MYSQL_ESCAPE_CHARS = re.compile(r'["()><~*+-]', re.UNICODE)
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RE_SPACE = re.compile(r"[\s]+", re.UNICODE)
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def escape_query(text, re_escape_chars):
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"""
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normalizes the query text to a format that can be consumed
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by the backend database
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"""
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text = force_text(text)
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text = RE_SPACE.sub(" ", text) # Standardize spacing.
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text = re_escape_chars.sub(" ", text) # Replace harmful characters with space.
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text = text.strip()
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return text
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class SearchBackend(six.with_metaclass(abc.ABCMeta)):
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"""Base class for all search backends."""
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def is_installed(self):
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"""Checks whether django-watson is installed."""
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return True
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def do_install(self):
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"""Executes the SQL needed to install django-watson."""
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pass
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def do_uninstall(self):
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"""Executes the SQL needed to uninstall django-watson."""
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pass
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requires_installation = False
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supports_ranking = False
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supports_prefix_matching = False
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def do_search_ranking(self, engine_slug, queryset, search_text):
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"""Ranks the given queryset according to the relevance of the given search text."""
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return queryset.extra(
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select={
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"watson_rank": "1",
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},
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)
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@abc.abstractmethod
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def do_search(self, engine_slug, queryset, search_text):
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"""Filters the given queryset according the the search logic for this backend."""
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raise NotImplementedError
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def do_filter_ranking(self, engine_slug, queryset, search_text):
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"""Ranks the given queryset according to the relevance of the given search text."""
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return queryset.extra(
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select={
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"watson_rank": "1",
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},
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)
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@abc.abstractmethod
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def do_filter(self, engine_slug, queryset, search_text):
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"""Filters the given queryset according the the search logic for this backend."""
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raise NotImplementedError
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def do_string_cast(self, connection, column_name):
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"""Casts the given column name to string."""
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return connection.ops.quote_name(column_name)
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class RegexSearchMixin(six.with_metaclass(abc.ABCMeta)):
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"""Mixin to adding regex search to a search backend."""
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supports_prefix_matching = True
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def do_search(self, engine_slug, queryset, search_text):
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"""Filters the given queryset according the the search logic for this backend."""
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word_query = Q()
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for word in search_text.split():
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regex = regex_from_word(word)
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word_query &= (Q(title__iregex=regex) | Q(description__iregex=regex) | Q(content__iregex=regex))
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return queryset.filter(
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word_query
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)
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def do_filter(self, engine_slug, queryset, search_text):
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"""Filters the given queryset according the the search logic for this backend."""
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model = queryset.model
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connection = connections[queryset.db]
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db_table = connection.ops.quote_name(SearchEntry._meta.db_table)
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model_db_table = connection.ops.quote_name(model._meta.db_table)
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pk = model._meta.pk
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id = connection.ops.quote_name(pk.db_column or pk.attname)
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# Add in basic filters.
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word_query = ["""
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({db_table}.{engine_slug} = %s)
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""", """
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({db_table}.{content_type_id} = %s)
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"""]
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word_kwargs = {
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"db_table": db_table,
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"model_db_table": model_db_table,
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"engine_slug": connection.ops.quote_name("engine_slug"),
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"title": connection.ops.quote_name("title"),
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"description": connection.ops.quote_name("description"),
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"content": connection.ops.quote_name("content"),
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"content_type_id": connection.ops.quote_name("content_type_id"),
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"object_id": connection.ops.quote_name("object_id"),
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"object_id_int": connection.ops.quote_name("object_id_int"),
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"id": id,
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"iregex_operator": connection.operators["iregex"],
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}
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word_args = [
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engine_slug,
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ContentType.objects.get_for_model(model).id,
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]
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# Add in join.
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if has_int_pk(model):
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word_query.append("""
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({db_table}.{object_id_int} = {model_db_table}.{id})
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""")
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else:
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word_query.append("""
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({db_table}.{object_id} = {model_db_table}.{id})
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""")
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# Add in all words.
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for word in search_text.split():
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regex = regex_from_word(word)
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word_query.append(
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"""
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({db_table}.{title} {iregex_operator}
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OR {db_table}.{description} {iregex_operator}
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OR {db_table}.{content} {iregex_operator})
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"""
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)
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word_args.extend((regex, regex, regex))
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# Compile the query.
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full_word_query = " AND ".join(word_query).format(**word_kwargs)
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return queryset.extra(
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tables=(db_table,),
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where=(full_word_query,),
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params=word_args,
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)
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class RegexSearchBackend(RegexSearchMixin, SearchBackend):
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"""A search backend that works with SQLite3."""
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class PostgresSearchBackend(SearchBackend):
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"""A search backend that uses native PostgreSQL full text indices."""
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search_config = getattr(settings, "WATSON_POSTGRES_SEARCH_CONFIG", "pg_catalog.english")
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"""Text search configuration to use in `to_tsvector` and `to_tsquery` functions"""
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def escape_postgres_query(self, text):
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"""Escapes the given text to become a valid ts_query."""
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return " & ".join(
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"$${0}$$:*".format(word)
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for word
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in escape_query(text, RE_POSTGRES_ESCAPE_CHARS).split()
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)
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def is_installed(self):
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"""Checks whether django-watson is installed."""
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connection = connections[router.db_for_read(SearchEntry)]
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cursor = connection.cursor()
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cursor.execute("""
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SELECT attname FROM pg_attribute
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WHERE attrelid = (SELECT oid FROM pg_class WHERE relname = 'watson_searchentry') AND attname = 'search_tsv';
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""")
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return bool(cursor.fetchall())
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@transaction.atomic()
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def do_install(self):
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"""Executes the PostgreSQL specific SQL code to install django-watson."""
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connection = connections[router.db_for_write(SearchEntry)]
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connection.cursor().execute("""
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-- Ensure that plpgsql is installed.
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CREATE OR REPLACE FUNCTION make_plpgsql() RETURNS VOID LANGUAGE SQL AS
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$$
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CREATE LANGUAGE plpgsql;
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$$;
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SELECT
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CASE
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WHEN EXISTS(
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SELECT 1
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FROM pg_catalog.pg_language
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WHERE lanname='plpgsql'
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)
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THEN NULL
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ELSE make_plpgsql() END;
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DROP FUNCTION make_plpgsql();
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-- Create the search index.
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ALTER TABLE watson_searchentry ADD COLUMN search_tsv tsvector NOT NULL;
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CREATE INDEX watson_searchentry_search_tsv ON watson_searchentry USING gin(search_tsv);
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-- Create the trigger function.
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CREATE OR REPLACE FUNCTION watson_searchentry_trigger_handler() RETURNS trigger AS $$
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begin
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new.search_tsv :=
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setweight(to_tsvector('{search_config}', coalesce(new.title, '')), 'A') ||
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setweight(to_tsvector('{search_config}', coalesce(new.description, '')), 'C') ||
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setweight(to_tsvector('{search_config}', coalesce(new.content, '')), 'D');
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return new;
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end
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$$ LANGUAGE plpgsql;
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CREATE TRIGGER watson_searchentry_trigger BEFORE INSERT OR UPDATE
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ON watson_searchentry FOR EACH ROW EXECUTE PROCEDURE watson_searchentry_trigger_handler();
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""".format(
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search_config=self.search_config
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))
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@transaction.atomic()
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def do_uninstall(self):
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"""Executes the PostgreSQL specific SQL code to uninstall django-watson."""
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connection = connections[router.db_for_write(SearchEntry)]
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connection.cursor().execute("""
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ALTER TABLE watson_searchentry DROP COLUMN search_tsv;
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DROP TRIGGER watson_searchentry_trigger ON watson_searchentry;
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DROP FUNCTION watson_searchentry_trigger_handler();
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""")
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requires_installation = True
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supports_ranking = True
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supports_prefix_matching = True
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def do_search(self, engine_slug, queryset, search_text):
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"""Performs the full text search."""
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return queryset.extra(
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where=("search_tsv @@ to_tsquery('{search_config}', %s)".format(
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search_config=self.search_config
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),),
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params=(self.escape_postgres_query(search_text),),
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)
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def do_search_ranking(self, engine_slug, queryset, search_text):
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"""Performs full text ranking."""
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return queryset.extra(
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select={
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"watson_rank": "ts_rank_cd(watson_searchentry.search_tsv, to_tsquery('{search_config}', %s))".format(
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search_config=self.search_config
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),
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},
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select_params=(self.escape_postgres_query(search_text),),
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order_by=("-watson_rank",),
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)
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def do_filter(self, engine_slug, queryset, search_text):
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"""Performs the full text filter."""
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model = queryset.model
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content_type = ContentType.objects.get_for_model(model)
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connection = connections[queryset.db]
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pk = model._meta.pk
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if has_int_pk(model):
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ref_name = "object_id_int"
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ref_name_typecast = ""
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else:
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ref_name = "object_id"
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# Cast to text to make join work with uuid columns
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ref_name_typecast = "::text"
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return queryset.extra(
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tables=("watson_searchentry",),
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where=(
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"watson_searchentry.engine_slug = %s",
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"watson_searchentry.search_tsv @@ to_tsquery('{search_config}', %s)".format(
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search_config=self.search_config
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),
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"watson_searchentry.{ref_name} = {table_name}.{pk_name}{ref_name_typecast}".format(
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ref_name=ref_name,
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table_name=connection.ops.quote_name(model._meta.db_table),
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pk_name=connection.ops.quote_name(pk.db_column or pk.attname),
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ref_name_typecast=ref_name_typecast
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),
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"watson_searchentry.content_type_id = %s"
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),
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params=(engine_slug, self.escape_postgres_query(search_text), content_type.id),
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)
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def do_filter_ranking(self, engine_slug, queryset, search_text):
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"""Performs the full text ranking."""
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return queryset.extra(
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select={
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"watson_rank": "ts_rank_cd(watson_searchentry.search_tsv, to_tsquery('{search_config}', %s))".format(
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search_config=self.search_config
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),
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},
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select_params=(self.escape_postgres_query(search_text),),
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order_by=("-watson_rank",),
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)
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def do_string_cast(self, connection, column_name):
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return "{column_name}::text".format(
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column_name=connection.ops.quote_name(column_name),
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)
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def escape_mysql_boolean_query(search_text):
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return " ".join(
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'+{word}*'.format(
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word=word,
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)
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for word in escape_query(search_text, RE_MYSQL_ESCAPE_CHARS).split()
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)
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class MySQLSearchBackend(SearchBackend):
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def is_installed(self):
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"""Checks whether django-watson is installed."""
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connection = connections[router.db_for_read(SearchEntry)]
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cursor = connection.cursor()
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cursor.execute("SHOW INDEX FROM watson_searchentry WHERE Key_name = 'watson_searchentry_fulltext'")
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return bool(cursor.fetchall())
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def do_install(self):
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"""Executes the MySQL specific SQL code to install django-watson."""
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connection = connections[router.db_for_write(SearchEntry)]
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cursor = connection.cursor()
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# Drop all foreign keys on the watson_searchentry table.
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cursor.execute(
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"SELECT CONSTRAINT_NAME FROM information_schema.TABLE_CONSTRAINTS "
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"WHERE CONSTRAINT_SCHEMA = DATABASE() "
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"AND TABLE_NAME = 'watson_searchentry' "
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"AND CONSTRAINT_TYPE = 'FOREIGN KEY'"
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)
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for constraint_name, in cursor.fetchall():
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cursor.execute(
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"ALTER TABLE watson_searchentry DROP FOREIGN KEY {constraint_name}".format(
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constraint_name=constraint_name,
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)
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)
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# Change the storage engine to MyISAM.
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cursor.execute("ALTER TABLE watson_searchentry ENGINE = MyISAM")
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# Add the full text indexes.
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cursor.execute("CREATE FULLTEXT INDEX watson_searchentry_fulltext "
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"ON watson_searchentry (title, description, content)")
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cursor.execute("CREATE FULLTEXT INDEX watson_searchentry_title "
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"ON watson_searchentry (title)")
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cursor.execute("CREATE FULLTEXT INDEX watson_searchentry_description "
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"ON watson_searchentry (description)")
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cursor.execute("CREATE FULLTEXT INDEX watson_searchentry_content "
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"ON watson_searchentry (content)")
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def do_uninstall(self):
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"""Executes the SQL needed to uninstall django-watson."""
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connection = connections[router.db_for_write(SearchEntry)]
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cursor = connection.cursor()
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# Destroy the full text indexes.
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cursor.execute("DROP INDEX watson_searchentry_fulltext ON watson_searchentry")
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cursor.execute("DROP INDEX watson_searchentry_title ON watson_searchentry")
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cursor.execute("DROP INDEX watson_searchentry_description ON watson_searchentry")
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cursor.execute("DROP INDEX watson_searchentry_content ON watson_searchentry")
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supports_prefix_matching = True
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requires_installation = True
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supports_ranking = True
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def _format_query(self, search_text):
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return escape_mysql_boolean_query(search_text)
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def do_search(self, engine_slug, queryset, search_text):
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"""Performs the full text search."""
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return queryset.extra(
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where=("MATCH (title, description, content) AGAINST (%s IN BOOLEAN MODE)",),
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params=(self._format_query(search_text),),
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)
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def do_search_ranking(self, engine_slug, queryset, search_text):
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"""Performs full text ranking."""
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search_text = self._format_query(search_text)
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return queryset.extra(
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select={
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"watson_rank": """
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((MATCH (title) AGAINST (%s IN BOOLEAN MODE)) * 3) +
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((MATCH (description) AGAINST (%s IN BOOLEAN MODE)) * 2) +
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((MATCH (content) AGAINST (%s IN BOOLEAN MODE)) * 1)
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""",
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},
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select_params=(search_text, search_text, search_text,),
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order_by=("-watson_rank",),
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)
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def do_filter(self, engine_slug, queryset, search_text):
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"""Performs the full text filter."""
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model = queryset.model
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content_type = ContentType.objects.get_for_model(model)
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connection = connections[queryset.db]
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pk = model._meta.pk
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if has_int_pk(model):
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ref_name = "object_id_int"
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else:
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ref_name = "object_id"
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return queryset.extra(
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tables=("watson_searchentry",),
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where=(
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"watson_searchentry.engine_slug = %s",
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"MATCH (watson_searchentry.title, watson_searchentry.description, watson_searchentry.content) "
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"AGAINST (%s IN BOOLEAN MODE)",
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"watson_searchentry.{ref_name} = {table_name}.{pk_name}".format(
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ref_name=ref_name,
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table_name=connection.ops.quote_name(model._meta.db_table),
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pk_name=connection.ops.quote_name(pk.db_column or pk.attname),
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),
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"watson_searchentry.content_type_id = %s",
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),
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params=(engine_slug, self._format_query(search_text), content_type.id),
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)
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def do_filter_ranking(self, engine_slug, queryset, search_text):
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"""Performs the full text ranking."""
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search_text = self._format_query(search_text)
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return queryset.extra(
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select={
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"watson_rank": """
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((MATCH (watson_searchentry.title) AGAINST (%s IN BOOLEAN MODE)) * 3) +
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((MATCH (watson_searchentry.description) AGAINST (%s IN BOOLEAN MODE)) * 2) +
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((MATCH (watson_searchentry.content) AGAINST (%s IN BOOLEAN MODE)) * 1)
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""",
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},
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select_params=(search_text, search_text, search_text,),
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order_by=("-watson_rank",),
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)
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class AdaptiveSearchBackend(SearchBackend):
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"""
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A search backend that guesses the correct search backend based on the
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DATABASES["default"] settings.
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"""
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def __new__(cls):
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"""Guess the correct search backend and initialize it."""
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connection = connections[router.db_for_read(SearchEntry)]
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if connection.vendor == "postgresql":
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return PostgresSearchBackend()
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if connection.vendor == "mysql":
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return MySQLSearchBackend()
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return RegexSearchBackend()
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