Horton

Re: Pluggable Storage - Andres's take

Haribabu Kommi <kommi.haribabu@gmail.com>

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From: Haribabu Kommi <kommi.haribabu@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-09-21T06:57:43Z
Lists: pgsql-hackers 
On Mon, Sep 10, 2018 at 5:42 PM Haribabu Kommi <kommi.haribabu@gmail.com>
wrote:

> On Wed, Sep 5, 2018 at 2:04 PM Haribabu Kommi <kommi.haribabu@gmail.com>
> wrote:
>
>>
>> On Tue, Sep 4, 2018 at 10:33 AM Andres Freund <andres@anarazel.de> wrote:
>>
>>> Hi,
>>>
>>> Thanks for the patches!
>>>
>>> On 2018-09-03 19:06:27 +1000, Haribabu Kommi wrote:
>>> > I found couple of places where the zheap is using some extra logic in
>>> > verifying
>>> > whether it is zheap AM or not, based on that it used to took some extra
>>> > decisions.
>>> > I am analyzing all the extra code that is done, whether any callbacks
>>> can
>>> > handle it
>>> > or not? and how? I can come back with more details later.
>>>
>>> Yea, I think some of them will need to stay (particularly around
>>> integrating undo) and som other ones we'll need to abstract.
>>>
>>
>> OK. I will list all the areas that I found with my observation of how to
>> abstract or leaving it and then implement around it.
>>
>
> The following are the change where the code is specific to checking whether
> it is a zheap relation or not?
>
> Overall I found that It needs 3 new API's at the following locations.
> 1. RelationSetNewRelfilenode
> 2. heap_create_init_fork
> 3. estimate_rel_size
> 4. Facility to provide handler options like (skip WAL and etc).
>

During the porting of Fujitsu in-memory columnar store on top of pluggable
storage, I found that the callers of the "heap_beginscan" are expecting
the returned data is always contains all the records.

For example, in the sequential scan, the heap returns the slot with
the tuple or with value array of all the columns and then the data gets
filtered and later removed the unnecessary columns with projection.
This works fine for the row based storage. For columnar storage, if
the storage knows that upper layers needs only particular columns,
then they can directly return the specified columns and there is no
need of projection step. This will help the columnar storage also
to return proper columns in a faster way.

Is it good to pass the plan to the storage, so that they can find out
the columns that needs to be returned? And also if the projection
can handle in the storage itself for some scenarios, need to be
informed the callers that there is no need to perform the projection
extra.

comments?

Regards,
Haribabu Kommi
Fujitsu Australia

Commits

  1. Add default_table_access_method to postgresql.conf.sample.

  2. tableam: Avoid relying on relation size to determine validity of tids.

  3. tableam: Don't assume that every AM uses md.c style storage.

  4. Allow pg_class xid & multixid horizons to not be set.

  5. Fix slot type issue for fuzzy distance index scan over out-of-core table AM.

  6. tableam: comment and formatting fixes.

  7. table: docs: fix typos and grammar.

  8. tableam: basic documentation.

  9. Only allow heap in a number of contrib modules.

  10. tableam: Add table_finish_bulk_insert().

  11. tableam: sample scan.

  12. tableam: bitmap table scan.

  13. tableam: Move heap specific logic from estimate_rel_size below tableam.

  14. tableam: VACUUM and ANALYZE support.

  15. tableam: relation creation, VACUUM FULL/CLUSTER, SET TABLESPACE.

  16. tableam: Support for an index build's initial table scan(s).

  17. tableam: Add table_get_latest_tid, to wrap heap_get_latest_tid.

  18. tableam: Add helper for indexes to check if a corresponding table tuples exist.

  19. tableam: Add and use table_fetch_row_version().

  20. tableam: Use in CREATE TABLE AS and CREATE MATERIALIZED VIEW.

  21. Ensure sufficient alignment for ParallelTableScanDescData in BTShared.

  22. Don't reuse slots between root and partition in ON CONFLICT ... UPDATE.

  23. Use a virtual rather than a heap slot in two places where that suffices.

  24. Store tuples for EvalPlanQual in slots, rather than as HeapTuples.

  25. Use slots in trigger infrastructure, except for the actual invocation.

  26. Store table oid and tuple's tid in tuple slots directly.

  27. Allow to use HeapTupleData embedded in [Buffer]HeapTupleTableSlot.

  28. Add ExecStorePinnedBufferHeapTuple.

  29. Add ArchiveOpts to pass options to ArchiveEntry

  30. Rename RelationData.rd_amroutine to rd_indam.

  31. Rephrase references to "time qualification".

  32. Move remaining code from tqual.[ch] to heapam.h / heapam_visibility.c.

  33. Move generic snapshot related code from tqual.h to snapmgr.h.

  34. Remove superfluous tqual.h includes.

  35. Don't duplicate parallel seqscan shmem sizing logic in nbtree.

  36. Move vacuumlazy.c into access/heap.

  37. Support parallel bitmap heap scans.