PostgreSQL index for row type

How are PostgreSQL strings and varchars indexed?

Is it indexing the entire "string" or just parts of it?

So far, I assumed it was using the full string, but never tested it.

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It uses the entire string. If you only want to use part of a string, you can always use an index for the expression . How:

CREATE INDEX some_idx ON tbl (left(col, 10));

      



left()

requires PostgreSQL 9.1 or newer. For older versions:

CREATE INDEX some_idx ON tbl (substr(col, 1,10));

      

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