Tom Lane wrote:
To review: Bruce is
proposing a var-length type structure with the properties
first byte 0xxxxxxx ---- field length 1 byte, exactly that value
first byte 1xxxxxxx ---- xxxxxxx data bytes follow
This can support *any* stored value from zero to 127 bytes long.
We can imagine creating new datatypes "short varchar" and "short char",
and then having the parser silently substitute these types for varchar(N)
or char(N) whenever N <= 127 / max_encoding_length. Add some
appropriate implicit casts to convert these to the normal varlena types
for computation, and away you go. No breakage of any existing
datatype-specific code, just a few additions in places like
heap_form_tuple.
I like this scheme a lot - maximum bang for buck.
Is there any chance we can do it transparently, without exposing new
types? It is in effect an implementation detail ISTM, and ideally the
user would not need to have any knowledge of it.
cheers
andrew
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