I tried creating a new table using liquibase schema in which one of the changeset item is to create index with statement.

<ext:createIndex tableName="wcruinfo" indexName="wcruinfo_emu_car_active_idx" where="active = TRUE" unique="true">
<column name="emucarid" />
</ext:createIndex>

I have followed the same kind of statement in ipinterface.xml on 1.6.0.

<ext:createIndex tableName="ipinterface" indexName="ipinterface_nodeid_ipaddr_notzero_idx" where="ipaddr != '0.0.0.0'" unique="true">
<column name="nodeid" />
<column name="ipaddr" />
</ext:createIndex>

The index is created on the table, but the where statement is missing. Same with ipinterface table as well.