On Tue, Mar 20, 2012 at 10:22 PM, Qi Huang <huangq...@hotmail.com> wrote:
> Thanks so much, Neil.
> I think I kind of understand the situation for now. The implementation
> posted by Neil was for the purpose of the talk, thus rushed and may not be
> up to st andard of Postgres Community. Also Neil mentioned the PRNG state in
> the patch is buggy, and maybe also some others. Thus, in the Gsoc project, I
> could understand the details of Neil's implementation, fix the bugs, make
> the code fit for the community standard, and test.
> Is there any comment on this?

In addition to that, you'll probably find that the old patch doesn't
apply any more, and you'll need to fix a lot of things to get it
working again.  The code has changed a lot in the meantime.

One thing we should probably try to establish before you get started
working on this is whether people want the feature, which is basically
the ability to write something like this in the FROM clause of a

table_name TABLESAMPLE { BERNOULLI | SYSTEM } ( sample_percent ) [
REPEATABLE ( repeat_seed ) ] ]

I have at present no position on whether we want that or not, but
maybe someone else does.  The upside is that would be a more efficient
replacement for the ORDER BY random() trick that is often used today;
the downside is that it requires dedicated syntax and a whole new
executor node for something that, realistically, isn't going to come
up very often.

Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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