From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)hub(dot)org |
Subject: | Re: [HACKERS] cidr |
Date: | 1998-07-21 15:18:59 |
Message-ID: | 24028.901034339@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> writes:
>> Would it make sense to use atttypmod to distinguish several different
>> subtypes of CIDR? "4 bytes", "4 bytes + mask", "6 bytes", "6 bytes
>> + mask" seem like interesting possibilities.
> Yes, that is the proper way to go, though atttypmod is something on
> column, not on each data row. It is specified when the column is
> created.
Right, that's what I had in mind. If you *know* that every entry in
your table only needs IPv4, you can specify that when making the table
and save a couple of bytes per entry.
The alternative solution is to make CIDR a variable-length type, but
I think the overhead of that would be as much or more than the possible
savings, no?
I don't know whether having multiple top-level types would be better
or worse than one type with a subtype code.
regards, tom lane
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