How many people have ordered the database column types explicitly for better disk packing?
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You mean nulls last? I did on oracle with (ugly) tables with lot of nulls.
Does it make a big difference in PostgreSQL?
dbfiddle.uk/?rdbms=postgre
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Not even that, was strictly reordering common datatypes. Oversimplified, but basically order things as:
ints/dates
shorts
booleans
numeric/text/other
varchar
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I think that it's fairly rare. The example that comes to mind is from Christopher Travers. Apparently Adjust applied this and other low-level optimizations. They were dealing with tens of terabytes of data.
I've definitely done that in the past when helping out postgres users, to pretty good effect. Both reducing table space and reducing query times (having fixed-width NOT NULL columns first can make tuple deforming a lot faster).
We really ought to make it easier to benefit here.
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Wonder if a first start would be a SRF showing the tuple layout for a table, including the padding space?
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