[HACKERS] BTree index and optimizer

[Anand, VJ (MED, GEMS-IT)]

        Hello:

        I am trying to find out, how is the B-tree index implemented for
multiple columns? does Postgres, just
        concatenate the columns --- if this is the case, then how is the
search performed? Also, does the optimizer
        choose the index, only when the constraining is on the leading
subset of the index column?

        Thanks
        VJ 

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