Re: pgsql: Skip full index scan during cleanup of B-tree indexes when possi

On Thu, Apr 5, 2018 at 2:26 PM, Alexander Korotkov <a.korotkov@postgrespro.ru> wrote:

On Thu, Apr 5, 2018 at 6:28 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Peter Geoghegan <pg@bowt.ie> writes:
>>> TRAP: FailedAssertion("!(metad->btm_version == 3)", File:
>>> "/home/pg/postgresql/root/build/../source/src/backend/access/nbtree/nbtpage.c",
>>> Line: 619)

>> Hm, buildfarm's not complaining --- what's the test case?

> This was discovered while testing/reviewing the latest version of the
> INCLUDE covering indexes patch. It now seems to be unrelated.

Oh, wait ... I wonder if you saw that because you were running a new
backend without having re-initdb'd?  Once you had re-initdb'd, then
of course there would be no old-format btree indexes anywhere.  But
if you hadn't, then anyplace that was not prepared to cope with the
old header format would complain about pre-existing indexes.

In short, this sounds like a place that did not get the memo about
how to cope with un-upgraded indexes.

That's an issue, because meta-page should be upgraded "on the fly".

That was tested, but perhaps without assertions.  I'll investigate more on

this an propose a fix.

So, "Assert(metad->btm_version == BTREE_VERSION)" was failed, because

metadata was copied from meta page to rel->rd_amcache "as is" with

metad->btm_version == BTREE_MIN_VERSION.

Without assert everything works fine, because extended metadata fields are

never used from rel->rd_amcache.  So my first intention was to relax this

assert to Assert(metad->btm_version >= BTREE_MIN_VERSION && metad->btm_version <= BTREE_VERSION).

But then I still have concern that we copy metadata beyond pd_lower

when metapage is in old format.

memcpy(rel->rd_amcache, metad, sizeof(BTMetaPageData));

This is why I decided to write separate function to handle caching of metadata,

which takes care about filling unavailable fields of metadata with default values.

I also made same fix for pageinspect.  Patch is attached.