RE: Global shared meta cache

Hi,
Thank you for handling it as CFM and sorry for waiting long time.

>-----Original Message-----
>From: Tomas Vondra [mailto:tomas(dot)vondra(at)2ndquadrant(dot)com]
>
>This patch was broken and waiting for author since early December, so I've marked it
>as returned with feedback. Feel free to resubmit an updated version to a future
>commitfest.

I couldn't make it until last January but now I resubmit this patch.
Previous version doesn't pass RT but now it passed.

Transaction consistency is controlled by invalidation messages
and location of cache.

As I mentioned before, for committed catalog tuple searching order is local memory
-> shared memory -> catalog file (either shared buffer or disk).
Local cache header has a pointer to global cache and we can use it.

But after system catalog is updated in transaction,
we need to make uncommitted-catalog-tuple cache from catalog file based on MVCC.
Searching for global cache should be skipped because global cache entry may be old
for that transaction.

So at the end of command local cache is invalidated as usual and in addition,
that process creates a dummy cache. This cache indicates that if found cache is only
this dummy one, we need to skip global search and search actual file.
Created uncommitted cache is located in local memory so that other process cannot find it.

- shared_memory_cotnext-v01.patch
Memory context for global system catalog cache and relation cache backed by DSA
- global_catalog_cache-v01.patch
For global system catalog

Things not included in this patch:
- sweep shared area logic
- global relation cache

Hope you have some comments!

Regards,
Takeshi Ideriha