在q for mortals chapter on data normalisation中，即消除列表中重复的任务，它建议使用枚举来查找列表中的不同值，因为它遍历整数的速度快于遍历变量长度的符号
u:`g`ibm`intl`msft / unique list of tickers
v:1000000?u / list with duplicate tickers
k:u?v / positions in u
\t:10 distinct v / performing distinct on symbols 10 times and timing
\t:10 distinct k / performing distinct on positions 10 times and timing
我发现distinct v比distinct k快得多，这与承诺的内容不一致。
感谢您的帮助。
答案 0 :(得分：2)
枚举通常用于保存到磁盘的数据以帮助压缩等 在那里，您将看到更大的性能提升。
KDB+ 3.5 2017.04.06 Copyright (C) 1993-2017 Kx Systems
Welcome to kdb+ 32bit edition
For support please see http://groups.google.com/d/forum/personal-kdbplus
Tutorials can be found at http://code.kx.com/wiki/Tutorials
To exit, type \\
To remove this startup msg, edit q.q
u:`g`ibm`intl`msft / unique list of tickers
v:1000000?u / list with duplicate tickers
q)k:`u$v //enumerate v against u
q)k
`u$`g`g`intl`ibm`intl`ibm`intl`msft`intl`ibm`g`msft`ibm`intl`intl`ibm`g`ibm`i..
q)save `:k
`:k
q)save `:u
`:u
q)save `:v
`:v
q)\\
KDB+ 3.5 2017.04.06 Copyright (C) 1993-2017 Kx Systems
Welcome to kdb+ 32bit edition
For support please see http://groups.google.com/d/forum/personal-kdbplus
Tutorials can be found at http://code.kx.com/wiki/Tutorials
To exit, type \\
To remove this startup msg, edit q.q
q)u:get `:u
q)\ts:10 distinct get `:v
462 8388848
q)\ts:10 distinct get `:k
37 4194544
q)
但你确实提出了一个有趣的问题，关于为什么在一个符号列表（在mem中）明显更快的一个整体列表。