mysql_query: fix false change reports when IF NOT EXISTS clause is used (#322)

* mysql_query: fix false change reports when IF NOT EXISTS clause is used

* Fix

* Fix doc, add fragment

* Improve doc

tests/integration/targets/test_mysql_query/tasks/mysql_query_initial.yml

@@ -321,6 +321,39 @@
       - result is changed
       - result.rowcount == [2]
 
+  # Issue https://github.com/ansible-collections/community.mysql/issues/268
+  - name: Create table
+    mysql_query:
+      <<: *mysql_params
+      login_db: '{{ test_db }}'
+      query: "CREATE TABLE issue268 (id int)"
+      single_transaction: yes
+
+  # Issue https://github.com/ansible-collections/community.mysql/issues/268
+  - name: Create table with IF NOT EXISTS
+    mysql_query:
+      <<: *mysql_params
+      login_db: '{{ test_db }}'
+      query: "CREATE TABLE IF NOT EXISTS issue268 (id int)"
+      single_transaction: yes
+    register: result
+
+  # Issue https://github.com/ansible-collections/community.mysql/issues/268
+  - assert:
+      that:
+      # PyMySQL driver throws a warning, so the following is correct
+      - result is not changed
+    when: connector.name.0 is search('pymysql')
+
+  # Issue https://github.com/ansible-collections/community.mysql/issues/268
+  - assert:
+      that:
+      # mysqlclient driver throws nothing, so it's impossible to figure out
+      # if the state was changed or not.
+      # We assume that it was for DDL queryes by default in the code
+      - result is changed
+    when: connector.name.0 is search('mysqlclient')
+
   - name: Drop db {{ test_db }}
     mysql_query:
       <<: *mysql_params