Sergei Dubov wrote:

This will automatically create a unique index on the primary key.

Well, if I do a query later like:

select * from table_a where table_b_id=1,

will the query use an index? Will this be true when I do join on this table?

Yes to both (if the query plan thinks that is the most efficient way).

Of course a query on "table_c_id" can't use the index.
--
  Richard Huxton
  Archonet Ltd

---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
      choose an index scan if your joining column's datatypes do not
      match

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