PostgreSQL composite primary key

Question

In MySQL, when I create a composite primary key, say with columns X, Y, Z, then all three columns become indexes automatically. Does the same happen for Postgre

Answer 1

Yes:

PostgreSQL automatically creates a unique index when a unique constraint or primary key is defined for a table. The index covers the columns that make up the primary key or unique constraint (a multicolumn index, if appropriate), and is the mechanism that enforces the constraint.