Thủ Thuật về Hướng dẫn mongodb fuzzy search Mới Nhất
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Nội dung chính
The text operator performs a full-text search using the analyzer that you specify in the index configuration. If you omit an analyzer, the text operator uses the default standard analyzer.
text has the following syntax:
$search: “index”: <index name>, // optional, defaults to “default” “text”: “query”: “<search-string>”, “path”: “<field-to-search>”, “fuzzy”: <options>, “score”: <options>, “synonyms”: “<synonyms-mapping-name>”
Field
Type
Description
Necessity
query
string or array of strings
The string or strings to search for. If there are multiple terms in a string, Atlas Search also looks for a match for each term in the string separately.
Required
path
string or array of strings
The indexed field or fields to search. You can also specify a wildcard path to search. See path construction for more information.
Required
fuzzy
document
Enable fuzzy search. Find strings which are similar to the search term or terms. You can’t use fuzzy with synonyms.
Optional
fuzzy.maxEdits
integer
Maximum number of single-character edits required to match the specified search term. Value can be 1 or 2. The default value is 2. Uses Damerau-Levenshtein distance.
Optional
fuzzy.prefixLength
integer
Number of characters the beginning of each term in the result that must exactly match. The default value is 0.
Optional
fuzzy.maxExpansions
integer
The maximum number of variations to generate and search for. This limit applies on a per-token basis. The default value is 50.
Optional
score
document
The score assigned to matching search term results. Use one of the following options to modify the score:
boost: multiply the result score by the given number.
constant: replace the result score with the given number.
Optional
synonyms
string
Required for running queries using synonyms.
Name of the synonym mapping definition in the index definition. Value can’t be an empty string. You can’t use fuzzy with synonyms.
text queries that use synonyms look for a conjunction (AND) of query tokens. text queries that don’t use synonyms search for a disjunction (OR) of query tokens. To run text queries that use synonyms and search for a disjunction (OR) of query tokens also, use the compound operator. For
example:
“compound”: “should”: [ “text”: “path”: “a”, “query”: “my query”, “synonyms”: “mySynonyms” , “text”: “path”: “a”, “query”: “my query” ]
Note
The amount of time that Atlas Search takes to execute queries that use synonym mappings depends on the number and size of documents in the synonym source collection. A query that uses a synonym mapping that is based on very few synonym documents might be faster than a query that uses a synonym mapping that is based on many synonym documents.
Optional
The Basic and Fuzzy examples below use the movies collection in the sample_mflix database. After loading the sample dataset into your cluster, create the Atlas Search index on the title field and run the example queries on your cluster.
Tip
The Synonyms examples below use the user_feedback.comments and user_feedback.synonyms collections and the index definition described in Define Synonym Mappings.
After loading the user_feedback.comments and user_feedback.synonyms collections and configuring the index definition for the collection, you can run the queries below.
The following Atlas Search example uses the text operator to search the title field in the movies collection for the term surfer.
Example
The following query searches the title field for the term surfer. It includes a $project stage to:
Exclude all fields except title
Add
a field named score
db.movies.aggregate([ $search: “text”: “path”: “title”, “query”: “surfer” , $project: “_id”: 0, “title”: 1, score: $meta: “searchScore” ])
The above query returns the following results:
“title” : “Soul Surfer”, “score” : 4.572484970092773 “title” : “Little Surfer Girl”, “score” : 3.9323642253875732 “title” : “Fantastic 4: Rise of the Silver Surfer”, “score” : 2.520784616470337
The following queries use the text operator to search the title field in the movies collection for terms that are within one character variation of each term in the query phrase naw
yark. Atlas Search returns different results depending on whether you use the default fuzzy options or define the maxExpansions, prefixLength, or maxEdits fields.
Click the
following tabs for example queries that use default and specified options:
The following examples use the text operator to search the comments field in the user_feedback.comments collection. Atlas Search returns results based on the type of mapping in the synonym source collection, user_feedback.synonyms, specified in the synonym mapping definition of the index for the user_feedback.comments collection.
Note
The following query searches the comments field for the word dress. It uses
the synonym mapping named mySynonyms in the index for the collection to also search for words that are configured to be synonyms of the word dress.
db.comments.aggregate([ $search: “text”: “path”: “comments”, “query”: “dress”, “synonyms”: “mySynonyms” ])
The preceding query returns the following results:
“_id” : ObjectId(“60e5f7d65f32d78cb3a3cc7a”), “type” : “apparel store”, “comments” : “Beautiful apparel for the bride.”
Atlas Search returns the above document because dress is configured to be synonym of apparel and attire using equivalent mappings in the synonym source collection, user_feedback.synonyms. Atlas Search returns the above document for searches on apparel and attire also because all
three words are configured to be synonyms of one another in the synonym source collection.
The following query searches the comments field for the word boat. It uses the synonym mapping named mySynonyms in the index for the collection to also search for words that are configured to be synonyms of the word boat.
db.comments.aggregate([ $search: “text”: “path”: “comments”, “query”: “boat”, “synonyms”: “mySynonyms” ])
The preceding query returns the following results:
“_id” : ObjectId(“60e5f7e25f32d78cb3a3cdc4”), “type” : “recreation rental”, “comments” : “Sails as well as the day it was made.”
Atlas Search returns the above document because boat is configured to
consider words boat, vessel, and sail as synonyms using explicit mappings in the synonym source collection, user_feedback.synonyms. However, Atlas Search doesn’t return any results for a query on vessel or sail because neither word is configured to consider any of the other words as synonyms.
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