作者
digoal
日期
2020-03-24
标签
PostgreSQL , Quantile
背景
https://github.com/tvondra/quantile
Quantile aggregates
This extension provides three simple aggregate functions to compute quantiles (http://en.wikipedia.org/wiki/Quantile). There are two forms of aggregate functions available - the first one returns a single quantile, the second one returns an arbitrary number of quantiles (as an array).
History
This extension was created in 2011, before PostgreSQL added functions to compute percentiles (percentile_cont and percentile_disc) in 9.4, which was released in December 2014. Even after introduction of those built-in functions it made sense to use this extension, because it was significantly faster in various cases.
The performance of the built-in functions improved a lot since then, and is usually very close or even faster than this extension. In some cases the extension is perhaps 2x faster than the built-in functions, but that may be (at least partially) attributed to not respecting work_mem.
It's therefore recommended to evaluate the built-in functions first, and only use this extension if it's provably (and consistently) faster than the built-in functions and the risk of running out of memory is low, or when it's necessary to support older PostgreSQL releases (pre-9.4) that do not have the built-in alternatives.
PostgreSQL 许愿链接
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PostgreSQL 解决方案集合
德哥 / digoal's github - 公益是一辈子的事.
