How to make FULL TEXT SEARCH more accurate using PHP - php

Question

I am implementing a search feature for my project. I am using a FULL TEXT SEARCH query to derive accurate results to User. I am beginner in PHP programming and I do not have enough information about FULL TEXT SEARCH.
This is my query:
$sql = $conn->prepare("SELECT *, MATCH(title, keyword) AGAINST(? IN BOOLEAN MODE) AS relevance FROM table ORDER BY relevance DESC LIMIT 20");
$sql->bind_param("s", $q);
$sql->execute();
$rs = $sql->get_result();
This query works good but this is only showing old results first instead of accurate results, and second thing is this query is not working correctly when the length of keyword is not more than 1 (e.g. keyword = Google).
Please do not give suggestions about Elastic search, Sphinx,
Algolia etc.

Answer 1

When MATCH() is used in a WHERE clause, the rows returned are automatically sorted with the highest relevance first.
So all you have to do is, remove the match from select and put it in where condition.
Source: https://dev.mysql.com/doc/refman/8.0/en/fulltext-natural-language.html

Answer 2

Why are you not using the sql like operator, I am providing you the example for multiple words in column named product in table named products
$db=mysqli_connect('localhost','root','','project');
$search=$_GET['userinput'];
$searcharray = explode(' ', $search);
$searchpdo=array();
$finalstate="";
foreach ( $searcharray as $ind=> $query){
$sql=array();
$exp='%'.$query.'%';
array_push($sql,"(title LIKE ?)");
array_push($searchpdo,$exp);
array_push($sql,"(keywords LIKE ?)");
array_push($searchpdo,$exp);
if($finalstate==""){
$finalstate = "(".implode(" OR ",$sql).")";
}
else{
$finalstate = $finalstate." AND "."(".implode(" OR ",$sql).")";
}
}
$stmt = $db->prepare("SELECT * FROM products WHERE (".$finalstate.") ");
$types=str_repeat('s',count($searchpdo));
$stmt->bind_param($types,...$searchpdo);
$stmt->execute();
$result = $stmt->get_result();
This will provide you the correct result with single word or multiple words

Answer 3

I think you have to tweak you query little bit and you would get desired results as under:
$sql = mysql_query("SELECT * FROM
patient_db WHERE
MATCH ( Name, id_number )
AGAINST ('+firstWord +SecondWord +ThirdWord' IN BOOLEAN MODE);");
and if you want to do exact search:
$sql = mysql_query("SELECT *
FROM patient_db
WHERE MATCH ( Name, id_number )
AGAINST ('"Exact phrase/Words"' IN BOOLEAN MODE);");
I had also posted the same answer in SO post somewhere but didn't know the post

Answer 4

There are multiple aspect to your question
If available, use mysql client to run the query instead of PHP first, until your query is ready to the like you want
If you recent documents (record) to show up on top of the search result, you need to change your ORDER BY clause. Currently, it is supposed to return the closest match (i.e. by relevance).
You need to strike a balance between relevance and recency (not clear how you define this) in your custom logic. A simple example that prioritize last week over last month and last month over the rest:
SELECT
....
, DATEDIFF (ItemDate, CURDATE() ) ItemAgeInDays
ORDER BY
relevance
* 100
* CASE
WHEN ItemAgeInDays BETWEEN 0 AND 7 --- last week
THEN 20
WHEN ItemAgeInDays BETWEEN 0 AND 30 --- last month
THEN 10
ELSE 1
END
DESC
You say single word item cannot be searched. In BOOLEAN MODE, you build a boolean logic for your search and such it uses special characters for that. For example +apple means 'apple' must exist. It is possible your single word might be conflicting with these characters.
Please review this reference, it explains the BOOLEAN MODE in great detail.
https://dev.mysql.com/doc/refman/8.0/en/fulltext-boolean.html
You say the query is not returning correct result. FULL TEXT search searches for your login in each document(row) and finds how many times it appears in each document. It then offset that by how many times your search appears in ALL documents. This means it prioritizes records where your search appears much more than the average. If your search is not distinguishing enough, it might seem not correct if most documents are similar to each in terms of that search. See the above link for more details.
BOOLEAN MODE does not sort the result by relevance by default. You need to add ORDER BY yourself, which you already did. Just wanted to note it here for others