PostgreSQL 10.0 preview 多核并行增强 - 索引扫描、子查询、VACUUM、fdw/csp钩子

1 minute read


PostgreSQL 9.6推出的多核并行计算特性,支持全表扫描,hash join,聚合操作。

10.0 在此基础上,增加了更多的支持。

1. Parallel bitmap heap scan

2. Parallel Index Scans

3. Parallel Merge Join

4. parallelize queries containing subplans

5. Block level parallel vacuum

6. Extending the parallelism for index-only scans

7. ParallelFinish Hook of FDW/CSP

这是一个fdw钩子,用于在访问FDW/CSP的node(backend process)的内存上下文释放前,让上面的gather node获得上下文的控制权。

从而,从DSM中获得每个fdw node通道的统计信息,比如pg_strom项目,custom scan阶段的dma数据传输的速度,GPU的运算时间等。


The attached patch implements the suggestion by Amit before.  
What I'm motivated is to collect extra run-time statistics specific  
to a particular ForeignScan/CustomScan, not only the standard  
Instrumentation; like DMA transfer rate or execution time of GPU  
kernels in my case.  
Per-node DSM toc is one of the best way to return run-time statistics  
to the master backend, because FDW/CSP can assign arbitrary length of  
the region according to its needs. It is quite easy to require.  
However, one problem is, the per-node DSM toc is already released when  
ExecEndNode() is called on the child node of Gather.  
This patch allows extensions to get control on the master backend's  
context when all the worker node gets finished but prior to release  
of the DSM segment. If FDW/CSP has its special statistics on the  
segment, it can move to the private memory area for EXPLAIN output  
or something other purpose.  
One design consideration is whether the hook shall be called from  
ExecParallelRetrieveInstrumentation() or ExecParallelFinish().  
The former is a function to retrieve the standard Instrumentation  
information, thus, it is valid only if EXPLAIN ANALYZE.  
On the other hands, if we put entrypoint at ExecParallelFinish(),  
extension can get control regardless of EXPLAIN ANALYZE, however,  
it also needs an extra planstate_tree_walker().  
Right now, we don't assume anything onto the requirement by FDW/CSP.  
It may want run-time statistics regardless of EXPLAIN ANALYZE, thus,  
hook shall be invoked always when Gather node confirmed termination  
of the worker processes.  
NEC OSS Promotion Center / PG-Strom Project  
KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>  




Flag Counter

digoal’s 大量PostgreSQL文章入口