PostgreSQL 11 preview - Faster partition pruning

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背景

目前PG社区版本内置分区表的性能受制于一些BIND、LOCK所有子表等问题，当分区过多时，性能会受到极大的影响。

《分区表锁粒度差异 - pg_pathman VS native partition table》

《PostgreSQL 查询涉及分区表过多导致的性能问题 - 性能诊断与优化(大量BIND, spin lock, SLEEP进程)》

不过还好pg_pathman这个插件弥补了以上问题。同时EDB发行的商用PG版本，在分区上面也有一些改进。

社区中，有一些committer关注到了这样的问题，同时提出了一些解法，已经将partition的选择代码进行了改造，采用的方法可能与EDB商用发型版本类似。

第一个相关patch如下

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=9fdb675fc5d2de825414e05939727de8b120ae81

Faster partition pruning    
    
Add a new module backend/partitioning/partprune.c, implementing a more    
sophisticated algorithm for partition pruning.  The new module uses each    
partition's "boundinfo" for pruning instead of constraint exclusion,    
based on an idea proposed by Robert Haas of a "pruning program": a list    
of steps generated from the query quals which are run iteratively to    
obtain a list of partitions that must be scanned in order to satisfy    
those quals.    
    
At present, this targets planner-time partition pruning, but there exist    
further patches to apply partition pruning at execution time as well.    
    
This commit also moves some definitions from include/catalog/partition.h    
to a new file include/partitioning/partbounds.h, in an attempt to    
rationalize partitioning related code.    
    
Authors: Amit Langote, David Rowley, Dilip Kumar    
Reviewers: Robert Haas, Kyotaro Horiguchi, Ashutosh Bapat, Jesper Pedersen.    
Discussion: https://postgr.es/m/098b9c71-1915-1a2a-8d52-1a7a50ce79e8@lab.ntt.co.jp    

这个patch还有一些连带的patch，未来社区版本的分区表应该不会再有bind, lock所有分区的问题了。

https://commitfest.postgresql.org/17/1330/