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

2014-07-19 6:26 GMT+08:00 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:

> =?UTF-8?B?5Zyf5Y2c55q/?= <pengcz(dot)nwpu(at)gmail(dot)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