title: Cannot create a woocommerce search based on custom meta fields
body: <p>I try to include in my default search custom fields. I followed the link here</p>
  
  <p><a href="http://jamescollings.co.uk/blog/extending-woocommerce-search-query-include-custom-fields/" rel="nofollow noreferrer">http://jamescollings.co.uk/blog/extending-woocommerce-search-query-include-custom-fields/</a></p>
  
  <p>I created a small plugin from it which gets my custom select field and custom text and I have the following</p>
  
  <pre><code>&lt;?php
  /**
  * Add sku, author, publisher and format to product search
  */
  
  // hook into wp pre_get_posts
  add_action('pre_get_posts', 'jc_woo_search_pre_get_posts');
  
  /**
  * Add custom join and where statements to product search query
  * @param  mixed $q query object
  * @return void
  */
  function jc_woo_search_pre_get_posts($q){
  
  if ( is_search() ) {
      add_filter( 'posts_join', 'jc_search_post_join' );
      add_filter( 'posts_where', 'jc_search_post_excerpt' );
  } 
  }
  
  /**
  * Add Custom Join Code for wp_mostmeta table
  * @param  string $join
  * @return string
  */
  function jc_search_post_join($join = ''){
  
  global $wp_the_query;
  
  // escape if not woocommerce searcg query
  if ( empty( $wp_the_query-&gt;query_vars['wc_query'] ) || empty( $wp_the_query-&gt;query_vars['s'] ) )
          return $join;
  
  $join .= "INNER JOIN wp_postmeta AS jcmt1 ON (wp_posts.ID = jcmt1.post_id)";
  return $join;
  }
  
  /**
  * Add custom where statement to product search query
  * @param  string $where
  * @return string
  */
  function jc_search_post_excerpt($where = ''){
  
  global $wp_the_query;
  
  // escape if not woocommerce search query
  if ( empty( $wp_the_query-&gt;query_vars['wc_query'] ) || empty( $wp_the_query-&gt;query_vars['s'] ) )
          return $where;
  
  $where = preg_replace("/post_title LIKE ('%[^%]+%')/", "post_title LIKE $1)
              OR (jcmt1.meta_key = '_sku' AND CAST(jcmt1.meta_value AS CHAR) LIKE $1)
              OR  (jcmt1.meta_key = '_text_field' AND CAST(jcmt1.meta_value AS CHAR) LIKE $1)
              OR  (jcmt1.meta_key = '_select' AND CAST(jcmt1.meta_value AS CHAR) LIKE $1 ", $where);
  
  return $where;
  }
  ?&gt;
  </code></pre>
  
  <p>But nothing happens how can I fix this
  thank you</p>