Log query and results

Great idea, thanks! That could really help a lot of people debugging their problems. Really strange that no-one thought of this before …

There are just a few small problems with your patch, but other than that it already looks great:

1. +++ b/includes/solr_connection.inc
   @@ -907,10 +907,18 @@ class SearchApiSolrConnection implements SearchApiSolrConnectionInterface {
   +    if ($this->options['log_query']) {
   +      watchdog('search_api_solr', $queryString, NULL, WATCHDOG_DEBUG);
   

   Here and in other places: please surround the array access with !empty(), otherwise people will receive PHP notices after upgrading, before re-saving the server.

2. +++ b/includes/solr_connection.inc
   @@ -918,7 +926,27 @@ class SearchApiSolrConnection implements SearchApiSolrConnectionInterface {
   +   * Helper function which logs response.
   +   *
   +   * @param $response
   +   *   the response received from Solr.
   

   This needs a clean-up regarding the Drupal documentation standards.

In any case, thanks again for creating this issue!

Looks good, thanks!
However, I now noted that watchdog() is used in a not-recommended way. I also rephrased the form field descriptions and had some other style cleanup. Please test/review and I can commit!

OK, committed.
Moving to D8 for porting.
Thanks again!

Just thought I'd mention solr_devel module... although that module currently shows a request in a block instead of logging it to watchdog.

In case anyone else lands here, it's worth noting there is some documentation here: https://www.drupal.org/node/2240049. It includes a robust example of logging using Solarium events.