On Thu, Mar 26, 2015 at 10:44 PM, hitesh ramani <hiteshram...@hotmail.com> wrote:
> Hello devs, > > I'm trying to understand how sorting exactly works in Postgres, I've > understood that there are two sorting mechanisms depending on the size of > the data, one being qsort which is initiated if workmem is < 1024 kb and > the other being external sort which is initiated in the other case. I tried > to find out more material to understand how it exactly works but I'm unable > to find any help material. > > Jim has answered this already. > Moreover, I'm trying to study the code using gdb by attaching it to the > pg_backend_pid and having a breakpoint at raw_parser, from where I start > analyzing. Any help material or resources would be really appreciated. > > In case of sort specifically, fire a query with an ORDER BY and break at ExecSort. Step through this function and its minions. Try range of sizes of results i.e. size of row * number of rows to understand the dynamics. > Thanks. > > --Hitesh > -- Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company
