[moving to -docs] On Wed, Oct 20, 2010 at 10:30 PM, Bruce Momjian <br...@momjian.us> wrote: > Josh Kupershmidt wrote: >> But it looks to me like effective_io_concurrency only affects bitmap >> heap scans. The setting from effective_io_concurrency gets put into >> "target_prefetch_pages" in ./src/backend/utils/misc/guc.c . But the >> only place which uses that variable is >> ./src/backend/executor/nodeBitmapHeapscan.c. >> >> The EnterpriseDB docs >> <http://www.enterprisedb.com/docs/en/8.3R2/perf/Postgres_Plus_Advanced_Server_Performance_Guide-17.htm> >> mention: >> "effective_io_concurrency is only used for Bitmap Heap Scans. For >> normal sequential scans the operating system should handle read-ahead >> internally (On Linux, see the blockdev command, in particular --setra >> and --setfra)." > > So, this this also true for community Postgres? Can someone suggest > updated docs?
It looks like effective_io_concurrency only has an impact on bitmap heap scans. I think a brief mention of this fact in the docs for effective_io_concurrency should suffice, patch attached. Josh
effective_io_concurrency-doc.patch
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