2010/4/24 Robert Haas <robertmh...@gmail.com>: > A couple of recent threads made got me thinking again about the idea > of global temporary tables. There seem to be two principal issues: > > 1. What is a global temporary table? > > 2. How could we implement that? > > Despite rereading the "idea: global temp tables" thread from April > 2009 in some detail, I was not able to get a clear understanding of > (1). What I *think* it is supposed to mean is that the table is a > permanent object which is "globally" visible - that is, it's part of > some non-temp schema like public or $user and it's column definitions > etc. are visible to all backends - and it's not automatically removed > on commit, backend exit, etc. - but the *contents* of the table are > temporary and backend-local, so that each new backend initially sees > it as empty and can then insert, update, and delete data independently > of what any other backend does. > > As to (2), my thought is that perhaps we could implement this by > instantiating a separate relfilenode for the relation for each backend > which accesses it. relfilenode would be 0 in pg_class, as it is for > "mapped" relations, but every time a backend touched the rel, we'd > allocate a relfilenode and associated the oid of the temp table to it > using some kind of backend-local storage - actually similar to what > the relmapper code does, except without the complexity of ever > actually having to persist the value; and perhaps using a hash table > rather than an array, since the number of mapped rels that a backend > can need to deal with is rather more limited than the number of temp > tables it might want to use.
it is good idea. I missing some ideas about statistics, about indexes. Regards Pavel Stehule > > Thoughts? > > ...Robert > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers > -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
