PostgreSQL 15 preview - 分区表裁剪优化, 未裁剪分区bitmapset - Track a Bitmapset of non-pruned partitions in RelOptInfo

作者

digoal

日期

2021-08-03

标签

PostgreSQL , 分区 , 裁剪

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=475dbd0b718de8ac44da144f934651b959e3b705

记录未裁剪列表, 降低plan time.

Track a Bitmapset of non-pruned partitions in RelOptInfo  
author  David Rowley <drowley@postgresql.org>     
Mon, 2 Aug 2021 23:47:24 +0000 (11:47 +1200)  
committer   David Rowley <drowley@postgresql.org>     
Mon, 2 Aug 2021 23:47:24 +0000 (11:47 +1200)  
commit  475dbd0b718de8ac44da144f934651b959e3b705  
tree    df2a34ed2a93b6be5f603e9b5c789762a1d42a7e    tree  
parent  a5cb4f9829fbfd68655543d2d371a18a8eb43b84    commit | diff  
Track a Bitmapset of non-pruned partitions in RelOptInfo  
For partitioned tables with large numbers of partitions where queries are  
able to prune all but a very small number of partitions, the time spent in  
the planner looping over RelOptInfo.part_rels checking for non-NULL  
RelOptInfos could become a large portion of the overall planning time.  
Here we add a Bitmapset that records the non-pruned partitions.  This  
allows us to more efficiently skip the pruned partitions by looping over  
the Bitmapset.  
This will cause a very slight slow down in cases where no or not many  
partitions could be pruned, however, those cases are already slow to plan  
anyway and the overhead of looping over the Bitmapset would be  
unmeasurable when compared with the other tasks such as path creation for  
a large number of partitions.  
Reviewed-by: Amit Langote, Zhihong Yu  
Discussion: https://postgr.es/m/CAApHDvqnPx6JnUuPwaf5ao38zczrAb9mxt9gj4U1EKFfd4AqLA@mail.gmail.com  
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