Merge pull request #4793 from vespa-engine/hmusum/deprecate-field-path-updates-with-variable-substitution

Deprecate variable substitution in field path updates

Author: hmusum

en/reference/schemas/document-field-path.html

@@ -48,7 +48,7 @@ <h2 id="maps-weighted-sets">Maps/weighted Sets</h2>
     </tr><tr>
       <th>&lt;mapfield&gt;{$&lt;variablename&gt;}</th>
       <td>Retrieve all values, setting the <a href="#variables">variable</a>
-        to the key value for each</td>
+        to the key value for each. {% include deprecated.html content="Deprecated, will be removed in Vespa 9."%}</td>
     </tr><tr>
       <th>&lt;mapfield&gt;.key</th>
       <td>Retrieve all key values</td>
@@ -76,7 +76,7 @@ <h2 id="array">Array</h2>
     </tr><tr>
       <th>&lt;arrayfield&gt;[$&lt;variablename&gt;]</th>
       <td>Retrieve all values in the array, setting the <a href="#variables">variable</a>
-        to the index of each</td>
+        to the index of each. {% include deprecated.html content="Deprecated, will be removed in Vespa 9."%}</td>
     </tr><tr>
       <th>&lt;arrayfield&gt;</th>
       <td>Retrieve all values in the array</td>
@@ -107,6 +107,7 @@ <h2 id="struct">Struct</h2>
 
 <h2 id="variables">Variables</h2>
 <p>
+{% include deprecated.html content="Deprecated, will be removed in Vespa 9."%}
 It can be useful to reference several field paths using a common variable.
 For instance, if you have an array of structs,
 you may want to use document selection on fields within the same array index together.