Re: how to reach D5 in tuplesort.c 's polyphase merge algorithm?

2014-07-19 6:26 GMT+08:00 Tom Lane <tgl@sss.pgh.pa.us>:

土卜皿 <pengcz.nwpu@gmail.com> writes:
>   for studying polyphase merge algorithm of tuplesort.c, I use ddd and
> apend a table, which has a schema as follows:

> ...

> and has 36684 records, and every record is like:
> id          code  article  name      department
> 31800    266    \N    Machault    77

> and for getting into external sort, I type the following command:

> select * from towns order by name desc;

> but I found it need not reach D5 and D6 during sorting,

That doesn't sound like enough data to force it to spill to disk at all;
at least not unless you turn down work_mem to some very small value.

 

hi, Tom

  thanks a lot!

                 

work_mem you said remind me one more thing I did, I tried to change BLCKSZ = 8192/2, and successfully compiled, but I got a error when executing initdb

Dillon