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.n...@gmail.com>: > > 2014-07-19 6:26 GMT+08:00 Tom Lane <t...@sss.pgh.pa.us>: > > =?UTF-8?B?5Zyf5Y2c55q/?= <pengcz.n...@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 >
