On 15 February 2017 at 08:07, Masahiko Sawada <sawada.m...@gmail.com> wrote:
> It's a bug. Attached latest version patch, which passed make check.

In its current form, I'm not sure this is a good idea. Problems...

1. I'm pretty sure the world doesn't need another VACUUM parameter

I suggest that we use the existing vacuum scale factor/4 to reflect
that indexes are more sensitive to bloat.

2. The current btree vacuum code requires 2 vacuums to fully reuse
half-dead pages. So skipping an index vacuum might mean that second
index scan never happens at all, which would be bad.

I suggest that we store the number of half-dead pages in the metapage
after each VACUUM, so we can decide whether to skip the scan or not.
And we use some math like each half-dead page that needs to be reused
is worth 250 index entries, so the decision to skip is based upon rows
and empty pages, not just recently vacuumed rows.

Simon Riggs                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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