Note that PostgreSQL uses the term “clustered index” to use something vaguely similar and yet very different to SQL Server.
If a particular index has been nominated as the clustering index for a table, then psql’s
\d command will indicate the clustered index, e.g.,
Indexes: "timezone_description_pkey" PRIMARY KEY, btree (timezone) CLUSTER
PostgreSQL does not nominate indices as clustering indices by default. Nor does it automatically arrange table data to correlate with the clustered index even when so nominated: the CLUSTER command has to be used to reorganise the table data.