SingleStore DB

MATCH

For tables created with a FULLTEXT index, the columnstore columns in that index can be searched through using the MATCH AGAINST syntax. MATCH takes a comma-separated list of column names and AGAINST takes an expression to filter the data. The result of the MATCH statement is a relevancy score between 0 and 1 indicating the quality of the match. A score closer to 1 indicates a higher quality match, while a score closer to 0 indicates a lower quality match.

The columns specified in a MATCH clause must be from the same table. To search against multiple tables, you need to specify multiple MATCH clauses. Additionally, full text search works best over English text and is case insensitive.

Important

If you need to include recent small inserts/updates from the hidden rowstore table in with your results, you should run OPTIMIZE TABLE tbl_name FLUSH before running your query.

See Full Text Search for more conceptual information on this feature.

Syntax
MATCH (<column1>,<column2>,...) AGAINST (<expression>)
Operators

The AGAINST expression consists of a mix of text with zero or more of the following operators.

Operator

Description

(no operator)

When no operator is specified, the word is optional; however, the rows that contain it are rated higher.

+

A leading plus sign indicates that this word must be present in each row returned.

-

A leading minus sign indicates that this word must not be present in any of the rows that are returned. Note: The - operator acts only to exclude rows that are otherwise matched by other search terms.

NOT

The NOT operator behaves the same as the - operator. The symbol ! can be used in place of the word NOT. The NOT operator must be in all caps.

AND

The AND operator matches documents where both terms exist anywhere in the text of a single document. This is equivalent to an intersection using sets. The symbol && can be used in place of the word AND. The expression A AND B is equivalent to +A +B. The AND operator must be in all caps.

OR

The OR operator behaves the same as not having any operator between words. The symbol || can be used in place of the word OR. The OR operator must be in all caps.

()

Parentheses group words into subexpressions. Parenthesized groups can be nested.

*, ?

See the Wildcard support section below.

""

A phrase that is enclosed within double quote (") characters matches the words in the quotes as if it is a single word. If the phrase contains no words that are in the index, the result is empty. The words might not be in the index because of a combination of factors: if they do not exist in the text, are stopwords, or are shorter than the minimum length of indexed words.

~

The tilde symbol is used to support fuzzy searches. To do a fuzzy search, use the tilde symbol at the end of a single-word term. For example, to search for a term similar in spelling to roam use the fuzzy search: roam~.

Important

Range searches and boosting terms to increase relevancy are not supported.

Note

SingleStore supports only constant expressions (search filters) inside the AGAINST clause, for example, a regular expression like (Stock*) or a constant string like "DBC". You may use stored procedures to accommodate for multiple search filters.

Stopwords

Certain words are ignored by full text search due to their commonality resulting in less relevant results. These are called stopwords. SingleStore’s default list of stopwords is as follows:

a, an, and, are, as, at, be, but, by, for, if, in, into, is, it, no, not, of, on, or, such, that, the, their, then, there, these, they, this, to, was, will, with
Wildcard Support

Single and multiple character wildcard searches within single terms are supported (not within phrase queries).

To perform a single character wildcard search use the ? symbol and to perform a multiple character wildcard search use the * symbol.

The single character wildcard search looks for terms that match that with the single character replaced. For example, to search for text or test you can use the search: te?t

Multiple character wildcard searches looks for zero or more characters. For example, to search for test, tests or tester, you can use the search: test* You can also use the wildcard searches in the middle of a term. te*t

Important

You cannot use a * or ? symbol as the first character of a search.

Special Characters

Depending on the use case, FULLTEXT matching may not always be compatible with match expressions involving special characters. This is because the default tokenizer for SingleStore’s FULLTEXT removes special characters from the search. The current list special characters are:

+ - && || ! ( ) { } [ ] ^ " ~ * ? : \

Warning

To escape these characters, use \\ before the character. Escaping a special character will prevent results that include a space in place of your special character. However, it will still include results that include a different special character. For example, a search against ‘Jo\-seph’ will not return the value ‘Jo seph’ but it will return ‘Jo*seph.’

The exception to this rule is that commas used to separate numbers like 1,000 or 12345,6789,12345 will not a have a negative effect on a search. This is true if the comma is present either in the search term, or in the result.

Relevancy Score

The relevancy score of an expression in a MATCH statement denotes the ranking of the expression based on the following factors:

  • Number of times an expression appears in a column. More occurrences of an expression in the matched column(s) increases its relevancy score.

  • Rarity of the expression. Rare words have a higher relevancy score than commonly used words.

  • The length of the column containing the expression. A column with a short expression has a higher relevancy score than a column with a long expression.

Examples

The following example searches for the word database across two columns:

CREATE TABLE articles (
    id INT UNSIGNED,
    year int UNSIGNED,
    title VARCHAR(200),
    body TEXT,
    KEY (id) USING CLUSTERED COLUMNSTORE,
    FULLTEXT (title, body));

SELECT * FROM articles
    WHERE MATCH (title,body)
    AGAINST ('database');

The following example combines MATCH with a SQL predicate:

CREATE TABLE books(
    id INT UNSIGNED,
    name VARCHAR(100),
    publish_year INT UNSIGNED,
    body TEXT,
    KEY (id) USING CLUSTERED COLUMNSTORE,  
    FULLTEXT(body));


SELECT count(*)
    FROM books
    WHERE publish_year = 2017 AND MATCH (body) AGAINST ('memsql');

The following example searches for either the word database or business intelligence:

SELECT title
    FROM articles  
    WHERE MATCH (title) AGAINST ('Database OR "Business Intelligence"');

The following example returns the title of an article that contains either database or Business Intelligence and the string real-time analytics in the body. The special character in real-time is not escaped in order to include results for both real time and real-time.

SELECT title
    FROM articles  
    WHERE MATCH (title) AGAINST ('Database OR "Business Intelligence"')
    AND MATCH(body) AGAINST ("real-time analytics");

This example shows a search for any id with the naming convention id-articleX, where X is the ID number. This search will return id-article1 or id-article227, but it will not return id-227. The special character is escaped here to avoid results including a space, since this violates the convention for assigning ids to each article. Note: This example requires a fulltext index on the id column rather than title, as indicated in the CREATE TABLE statement above.

SELECT title
    FROM articles  
    WHERE MATCH(article_id) AGAINST ('"id\\-" +article*');

This example uses the wildcard ’*’ to return all articles with titles starting with the word Journal such as Journalism, Journalist, Journals, and so on.

SELECT *
    FROM articles  
    WHERE MATCH(title) AGAINST ('Journal*');

This example returns the articles where the title starts with Data and also contains the word function. So, the search result includes words like Database function and Database functions.

SELECT title
    FROM articles  
    WHERE MATCH (title) AGAINST ('+Data* AND function?');

In the following example, the special character - is escaped to include all results starting with Data-, followed by words starting with di. So, the search result includes words like Data-directory, Data-dictionary, and so on.

SELECT * FROM articles WHERE MATCH(title) AGAINST ('+Data\\- +di*');   

This example uses the relevance score as an output column:

SELECT id, title, MATCH(body) AGAINST ('database') relevance
    FROM articles
    WHERE MATCH(body) AGAINST ('database')

This example returns matches greater than a specific relevance score:

SELECT id, title, MATCH(body) AGAINST ('database')
    FROM articles
    WHERE MATCH(body) AGAINST ('database') > .12;

MATCH can also be used with UPDATE or DELETE queries.

UPDATE articles set name = concat(name,".DATABASE") where MATCH(body) AGAINST ('database');

DELETE from articles where MATCH(body) AGAINST ('database');