In addition to the comment of MatsLindh, to add an unidirectional synonym like: "android=>android,smartphone", you should also consider to add the Synonym Filter only at index time and not both at index and query time
For example:
<analyzer type="index">
...
<filter class="solr.SynonymGraphFilterFactory" synonyms="synonyms.txt"/>
...
</analyzer>
This way, both "android" and "smartphone" will be indexed for any occurrence of "android"
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…