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Excuse the noob question, I couldn’t find any reading
material on this topic. Let’s say my_table has two fields, pkey_id and another_id.
The primary key is pkey_id and of course indexed. Then someone adds a composite index on btree(pkey_id, another_id). Question 1) Is there any benefit to having pkey_id in the
second index (assuming the index was created to satisfy some arbitrary WHERE
clause)? Question 2) Regardless of the answer to Question 1 - if
another_id is not guaranteed to be unique, whereas pkey_id is – there any
value to changing the order of declaration (more generally, is there a
performance impact for column ordering in btree composite keys?) Thanks, Carlo |
