Brian Hurt wrote:
Tom Lane wrote:
"Florian G. Pflug" <[EMAIL PROTECTED]> writes:
...
Neither the "dealer", nor the "workers" would need access to the either
the shared memory or the disk, thereby not messing with the "one backend
is one transaction is one session" dogma.
...
Unfortunately, this idea has far too narrow a view of what a datatype
input function might do. Just for starters, consider "enum" input,
which certainly requires catalog access. We have also explicitly
acknowledged the idea that datatype I/O functions might try to store
typmod-related data in some special catalog somewhere.
Would it be possible to determine when the copy is starting that this
case holds, and not use the parallel parsing idea in those cases?
In theory, yes. In pratice, I don't want to be the one who has to answer
to an angry user who just suffered a major drop in COPY performance
after adding an ENUM column to his table.
I was thinking more along the line of letting a datatype specify a
function "void* ioprepare(typmod)" which returns some opaque object
specifying all that the input and output function needs to know.
We could than establish the rule that input/output functions may not
access the catalog, and instead pass them a pointer to that opaque object.
All pretty pie-in-the-sky at the moment, though...
regards, Florian Pflug
---------------------------(end of broadcast)---------------------------
TIP 6: explain analyze is your friend
