Re: [GENERAL] Re: have trouble understanding xmin and xmax with update operations from two different sessions

On Mon, Jul 3, 2017 at 10:39 AM, rajan wrote: > Thanks, Jeff. > > Now I am going back to my old question. > > Even though *Session 2* fails to update with UPDATE 0 message, its txid is > saved in xmax of updated(by *Session 1*) tuple. > > As it becomes an old txid, how come

[GENERAL] Re: have trouble understanding xmin and xmax with update operations from two different sessions

Thanks, Jeff. Now I am going back to my old question. Even though *Session 2* fails to update with UPDATE 0 message, its txid is saved in xmax of updated(by *Session 1*) tuple. As it becomes an old txid, how come new txids are able to view it? - -- Thanks, Rajan. -- View this message in

Re: [GENERAL] Re: have trouble understanding xmin and xmax with update operations from two different sessions

On Mon, Jul 3, 2017 at 3:02 AM, rajan wrote: > Thanks for the explanation. > > will I be able to view the information using this function, > SELECT * FROM heap_page_items(get_raw_page('testnumbers', 0)); > > Also, please let me know which column I should refer for viewing the

[GENERAL] Re: have trouble understanding xmin and xmax with update operations from two different sessions

Thanks for the explanation. will I be able to view the information using this function, SELECT * FROM heap_page_items(get_raw_page('testnumbers', 0)); Also, please let me know which column I should refer for viewing the pointer. - -- Thanks, Rajan. -- View this message in context:

Re: [GENERAL] Re: have trouble understanding xmin and xmax with update operations from two different sessions

On Sat, Jul 1, 2017 at 8:55 PM, rajan wrote: > Thanks, Jeff. That helps understanding it 50%. > > *Session 2* fails to UPDATE the record which is in *(0,2)* and this tuple > is > marked for deletion. It means that *(0,2) never exists* when Session 2 is > trying to perform the

[GENERAL] Re: have trouble understanding xmin and xmax with update operations from two different sessions

Thanks, Jeff. That helps understanding it 50%. *Session 2* fails to UPDATE the record which is in *(0,2)* and this tuple is marked for deletion. It means that *(0,2) never exists* when Session 2 is trying to perform the update. In that case, how *Session 3's new row (0,4)* contains the xmax as

Re: [GENERAL] Re: have trouble understanding xmin and xmax with update operations from two different sessions

On Sat, Jul 1, 2017 at 6:32 PM, rajan wrote: > hello, > > thanks for replies, Adrian, Steven. > > >So calling it can advance the xid manually. Some testing here showed > >that what xmin or xmax is created depends on when you call txid_current > >in either the original session

[GENERAL] Re: have trouble understanding xmin and xmax with update operations from two different sessions

hello, thanks for replies, Adrian, Steven. >So calling it can advance the xid manually. Some testing here showed >that what xmin or xmax is created depends on when you call txid_current >in either the original session or the concurrent sessions. I understand this and I am executing my