Hello, What enhancement will be necessary to implement similar feature of partial seq-scan using custom-scan interface?
It seems to me callbacks on the three points below are needed. * ExecParallelEstimate * ExecParallelInitializeDSM * ExecParallelInitializeWorker Anything else? Does ForeignScan also need equivalent enhancement? Background of my motivation is the slides below: http://www.slideshare.net/kaigai/sqlgpussd-english (LT slides in JPUG conference last Dec) I'm under investigation of SSD-to-GPU direct feature on top of the custom-scan interface. It intends to load a bunch of data blocks on NVMe-SSD to GPU RAM using peer-to-peer DMA, prior to data loading onto CPU/RAM. (Probably, it shall be loaded only all-visible blocks like as index-only scan.) Once we load the data blocks onto GPU RAM, we can reduce rows to be filtered out later but consumes CPU RAM. An expected major bottleneck is CPU thread which issues the peer-to-peer DMA requests to the device, rather than GPU tasks. So, utilization of parallel execution is a natural thought. However, a CustomScan node that takes underlying PartialSeqScan node is not sufficient because it once loads the data blocks onto CPU RAM. P2P DMA does not make sense. The expected "GpuSsdScan" on CustomScan will reference a shared block-index to be incremented by multiple backend, then it enqueues P2P DMA request (if all visible) to the device driver. Then it receives the rows only visible towards the scan qualifiers. It is almost equivalent to SeqScan, but wants to bypass heap layer to utilize SSD-to-GPU direct data translation path. Thanks, -- NEC Business Creation Division / PG-Strom Project KaiGai Kohei <kai...@ak.jp.nec.com> -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
