Minor: Plugin: SurveyExportCSV: Extend README information - refs BT#15280

documentation/optimization.html

@@ -200,6 +200,7 @@ ALTER TABLE c_lp_item_view ADD INDEX idx_clpiv_c_i_v (c_id, id, view_count);
         CREATE INDEX idx_survey_code ON c_survey (code);
         CREATE INDEX idx_survey_inv_code ON c_survey_invitation (survey_code);
         CREATE INDEX idx_survey_qo_qid ON c_survey_question_option (question_id);
+        CREATE INDEX idx_c_survey_answerucsq ON c_survey_answer (user, c_id, survey_id, question_id);
     </pre>
     Also by adding a index on access_url_rel_session to improve the course/session list
     <pre>

plugin/surveyexportcsv/README.md

@@ -1,10 +1,29 @@
 # Survey Export CSV
 
-Export surveys to CSV file.
+Exports survey results to a CSV file with a very specific format.
 
-This plugin will add a new action button in survey list allowing export the survey.
+This plugin will add a new action button in the surveys list, allowing the 
+teacher to export the survey in a CSV format meant at exchanging with external
+analysis tools.
 
-**Instructions**
+The CSV format looks this way:
+
+```
+DATID;P01;P02;P03;P04;P05;P06;P07;P08;DATOBS
+1;"1";"2";"26";"10";"2";"2";"2";"4";"2"
+2;"1";"2";"32";"10";"6";"4";"4";"5";"2"
+3;"2";"3";"27";"8";"5";"5";"2";"5";"1"
+4;"1";"3";"33";"11";"1";"4";"1";"6";"1"
+```
+
+Where:
+- DATID represents a sequential ID for the participants (not related to
+their internal user ID)
+- P01,P02,... represent the sequential ID of each question inside the survey
+- DATOBS represents the free answer of the user to an open remarks form at 
+the end of the survey
+
+**Setup instructions**
 
 - Install plugin
 - Set enabled in configuration
@@ -15,3 +34,9 @@ This plugin will add a new action button in survey list allowing export the surv
       'SurveyExportCSVPlugin' => ['SurveyExportCsvPlugin', 'filterModify'],
   ];
   ```
+If you have large surveys with large numbers of users answering them, you
+might want to ensure your c_survey_answer table is properly indexed. If not,
+use the following SQL statement to modify that:
+```sql
+alter table c_survey_answer add index idx_c_survey_answerucsq (user, c_id, survey_id, question_id);
+```