Re: doc fixes: vacuum_cleanup_index_scale_factor

On Tue, May 1, 2018 at 10:30 PM, Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> - When no tuples were deleted from the heap, B-tree indexes might still
> - be scanned during <command>VACUUM</command> cleanup stage by two
> - reasons. The first reason is that B-tree index contains deleted pages
> - which can be recycled during cleanup. The second reason is that B-tree
> - index statistics is stalled. The criterion of stalled index statistics
> - is number of inserted tuples since previous statistics collection
> - is greater than <varname>vacuum_cleanup_index_scale_factor</varname>
> - fraction of total number of heap tuples.
> + When no tuples were deleted from the heap, B-tree indexes are still
> + scanned during <command>VACUUM</command> cleanup stage unless
> + two conditions are met. First, if a B-tree index contains no deleted pages
> + which can be recycled during cleanup. Second, if B-tree
> + index statistics are not stale. Index statistics are considered stale unless
> + <varname>vacuum_cleanup_index_scale_factor</varname> is non-negative, and the
> + number of inserted tuples since the previous statistics collection is
> + less than that fraction of the total number of heap tuples.
> + The default is -1, meaning index scan during cleanup is not skipped.

I agree that this documentation needs to be rewritten but your rewrite
doesn't strike me as very good English either. A sentence of the form
"First, if I like hamburgers." is not correct English.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company