title: liquibase: check for compound indexes by columns
body: <p>We are trying to check in a liquibase precondition if a compound index already exists, before we create it. Reason is: the company we sold the software to ran optimization changesets on our db, which we now want to include in our db as well. But we do not know the name of the indexes that they used.</p>
  
  <p>We have this so far:</p>
  
  <pre><code>&lt;changeSet id="changeset-id" author="great-author"&gt;
      &lt;preConditions onFail="MARK_RAN"&gt;
          &lt;not&gt;
              &lt;and&gt;
                  &lt;indexExists indexName="idx_fields"/&gt;
                  &lt;indexExists tableName="my_table" columnNames="id,name"/&gt;
              &lt;/and&gt;
          &lt;/not&gt;
      &lt;/preConditions&gt;
      &lt;createIndex tableName="my_table" indexName="idx_fields"&gt;
          &lt;column name="id"/&gt;
          &lt;column name="name"/&gt;
      &lt;/createIndex&gt;
  &lt;/changeSet&gt;
  </code></pre>
  
  <p>now when the customer ran this change manually on this db:</p>
  
  <pre><code>create index company_schema.IDX1_FIELDS on company_schema.MY_TABLE("ID", "NAME") TABLESPACE USERS;
  </code></pre>
  
  <p>Then our changesets are failing and deployment is stuck.</p>
  
  <p>Seems like our second precondition that is checking for a compound index by column names is not working.</p>
  
  <p>Who can help us here?</p>