Q:

Utilizing parallel query execution in Postgresql for SELECT INTO

Is parallel query execution in Postgresql supported for SELECT INTO queries?

A:

No. Parallel execution is not available for DDL statements - only for read only queries.
The deprecated SELECT .. INTO ... creates a new table and thus it qualifies as DDL.
It is also recommended to use CREATE TABLE .. AS SELECT ... instead.
Update: Postgres 11 (to be released end of 2018) will support parallel query execution for CREATE TABLE ... AS SELECT ...

