Re: Toast, Text, blob bytea Huh?

Peter T Mount wrote:
> Quoting Joe Conway <joseph(dot)conway(at)home(dot)com>:
>
> > TEXT is a datatype which stores character data of unspecified length (up
> > to
> > the max value of a 4 byte integer in length, although I've seen
> > comments
> > indicating that the practical limit is closer to 1 GB -- not sure why).
>
> It may be something to do with the 1Gb splitting of the physical files
> representing a table... Unless it changed recently, a table was split over
> multiple files at the 1Gb mark.

No, it's because the upper two bits of the variable size
field are used as flags.

But in practice there are other limits that force you to keep
the objects you throw into text or bytea fields alot smaller.
When your INSERT query is received, parsed, planned and a
heap tuple created, there are at least four copies of that
object in the backends memory. How much virtual memory does
your OS support for one single process?

And by the way, TOAST is not only used for character data
types. All variable size data types in the base system are
toastable. Well, arrays might be considered sort of pop-tarts
here, but anyway, they get toasted.

Jan

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