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

hi,
I got the same result after work_mem = 64,
but I can get to D5 and D6 after using bigger data sample (at least 100000
records) as Tom said!

2014-07-19 6:35 GMT+08:00 土卜皿 <pengcz(dot)nwpu(at)gmail(dot)com>:

>
> 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
>