Why WP_Query's 's'=>'keyword' searches only for 'post_title' and why not 'post_content'?

Question

I have written a search query for my custom post. I am using search parameter of WP_Query for this then it has to search for both 'post_title' & 'post_content' but it is searching only for 'post_title' and not searching the 'post_content'. below is my code :

$institute_name = get_user_meta($user_ID, 'inistitute_name', true);
//add_filter( 'posts_where' , array($this,'posts_where' ));     this line Irritated me.
$paged = (get_query_var('page')) ? get_query_var('page') : 1;
$args = array(
     'post_type' => 'mypost',
     array( 's' => $keyword ),
    'meta_query' => array (
      array (
           'key' => 'inistitute_name',
           'value' => array ($institute_name),
           'compare' => 'IN'
      )
    ),
   'posts_per_page' => -1,
   'paged' => $paged,
   'post_status' => 'publish',
);
$the_query = new WP_Query($args);
//remove_filter( 'posts_where',  array($this,'posts_where' ));
echo "<pre>";
print_r($the_query);
echo "</pre>";

If I print that result then I am getting the query like below:

SELECT wp_dxwe_posts.* FROM wp_dxwe_posts INNER JOIN wp_dxwe_postmeta ON 
( wp_dxwe_posts.ID = wp_dxwe_postmeta.post_id ) WHERE 1=1  AND 
( (wp_dxwe_postmeta.meta_key = 'inistitute_name' AND 
CAST(wp_dxwe_postmeta.meta_value AS CHAR) IN ('ITeLearn') )) 
AND wp_dxwe_posts.post_type = 'mypost' AND ((wp_dxwe_posts.post_status = 'publish')) AND 
post_title LIKE '%launch%' GROUP BY wp_dxwe_posts.ID 
ORDER BY wp_dxwe_posts.post_date DESC 

As I said it is working fine for only 'post_title' but sometimes not working, it is not always working. Can anyone please tell me what's wrong in this code? Thanks in advance.

Update: below is the 'post_where' method I found in the same file. I think Either its better to remove this method or don't call the 'posts_where' method by 'add_filter' method. Finally, I got the solution by commenting the 'add_filter' & 'remove_filter' code lines. But could u please tell me bit briefly about 'add_filter' method? will I get any problem as I commented the 'add_filter' method.? I am Updating the above code.

function posts_where( $where ) {

    if(isset($_GET['tewa_search'])) {
        $var=$_GET['tewa_search'];
        $where .= " AND post_title LIKE '%".$var."%'";
    }

    return $where;
}

Answer 1

WP_Query's s parameter in it's arguments IS used to search the post_content too.

There must be something that is altering this behaviour.

Looks like there's a method inside your class that is altering the query: posts_where.

Or maybe it's that you've put the s argument into an array of it's own, rather than being part of the $args array itself.

The posts_where filter allows you to edit the SQL search query, before it is sent. Removing that code shouldn't 'break' your code, but will probably produce different results.