Re: Using multi-row technique with COPY

On Sun, 2005-11-27 at 17:45 -0500, Tom Lane wrote:
> Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> > COPY FROM can read in sufficient rows until it has a whole block worth
> > of data, then get a new block and write it all with one pair of
> > BufferLock calls.
>
> > Comments?
>
> I don't see any way to do this without horrible modularity violations.
> The COPY code has no business going anywhere near individual buffers;
> for that matter, it doesn't even really know what "a block worth" of
> data is, since the tuples it's dealing with aren't toasted yet.

I've taken on board your comments about modularity issues from earlier.
[I've not included anything on unique indexes, notice]

I was expecting to buffer this in the heap access method with a new
call, say, heap_bulk_insert() rather than have all that code hanging
around in COPY. A lower level routine RelationGetBufferForTupleArray can
handle the actual grunt. It can work, without ugliness.

We'd need to handle a buffer bigger than a single tuple anyway, so you
keep adding tuples until the last one tips over the edge, which then
gets saved for the next block. Heap access method knows about blocks.

We could reasonably do a test for would-be-toasted within those
routines. I should have said that this wouldn't apply if any of the
tuples require toasting, which of course has to be a dynamic test.

COPY would only need to know whether it was invoking the normal or the
bulk mode, which is reasonable, since it knows about indexes, triggers
etc.

Best Regards, Simon Riggs