2015-07-15 15:21 GMT+02:00 Zhaomo Yang <zhy...@cs.ucsd.edu>: > > Sounds fine in general. I'm a bit curious to know what are the locking > implications of > vivifying the table on access. > > The locking implications depend on how we interpret the existing commands > in the context of global temp tables and I think we should discuss and > agree on the behaviors of the commands with global temp tables, but I think > in general we can follow these rules: > > If the command executes on the global temp table's metadata, for example > an ALTER TABLE command, then we lock the global copy at the same level as > we do a regular table. >
there is other question - what is effect of ALTER TABLE of global temp table on instances of this table in active sessions? > > If the command executes on the global temp table's data (which is actually > stored in the session copy), for example an DML command, then the global > copy is locked at the AccessShareLock level to prevent concurrent > modifications to the global temp table's definition from other sessions. > > Thanks, > Zhaomo > > On Wed, Jul 15, 2015 at 4:26 AM, Andrew Dunstan <and...@dunslane.net> > wrote: > >> >> On 07/15/2015 07:58 AM, Simon Riggs wrote: >> >> >>> For me the design summary is this >>> >>> * CREATE GLOBAL TEMP TABLE creates catalog entries like a normal table >>> but with different relkind >>> * When we see a request to INSERT, DEL, UPD, SEL from the temp table, if >>> it does not exist we create it as a TEMP table of the same name, using the >>> Global's pg_class entry as a template >>> >>> That meets the SQL Standard and doesn't contain any visibility problems >>> or need for new internals. >>> >>> The purpose of this feature is to automatically create a temp table with >>> the same definition whenever needed. The discussion of "bloat" is just >>> wrong. We create exactly the same amount of bloat as if we had typed CREATE >>> TEMP TABLE. Optimising temp table entries in the catalog is another, >>> separate patch, if we care. >>> >>> >>> >> Sounds fine in general. I'm a bit curious to know what are the locking >> implications of vivifying the table on access. >> >> cheers >> >> andrew >> > >
