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Date: Sat, 26 Dec 1998 22:36:53 -0500 (EST)
From: Jan Vicherek <honza(at)ied(dot)com>
To: pgsql-hackers(at)postgreSQL(dot)org
Subject: [HACKERS] space usage of NULL fields
Message-Id: <Pine(dot)LNX(dot)4(dot)04(dot)9812262213380(dot)11035-100000(at)ann(dot)ied(dot)com>
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Hello,

a quick question (I couldn't contact postgresql.org, so I didn't check
the FAQ, but I doubt it would be there.)

When I create a table with field "nnn float8" and total row size, say
140 bytes, and then I insert a row with NULL in this field, will my record
take up those 8 bytes in physical page (say 140 bytes) or will it take up
less (like 140-8=132), i.e. will it be shortened by those 8 bytes, since
the value is NULL and no information is stored in that field ? ( I *hate*
run-on sentences :)

In general, what are the savings/overheads associated in PG with
NULL/not NULL fields ? I.e. if will I save the space if I define the field
as varchar(8) instead of float8 ?

Thanx,

Jan

-- Gospel of Jesus is the saving power of God for all who believe --
## To some, nothing is impossible. ##
http://Vicherek.Waterloo.on.ca/