Horton

Re: Pluggable Storage - Andres's take

P <apraveen@pivotal.io>

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From: Asim R P <apraveen@pivotal.io>
To: PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Cc: Ashwin Agrawal <aagrawal@pivotal.io>, 9erthalion6@gmail.com, kommi.haribabu@gmail.com, Andres Freund <andres@anarazel.de>, alvherre@2ndquadrant.com, a.korotkov@postgrespro.ru
Date: 2018-11-22T02:12:04Z
Lists: pgsql-hackers 
Ashwin (copied) and I got a chance to go through the latest code from
Andres' github repository.  We would like to share some
comments/quesitons:

The TupleTableSlot argument is well suited for row-oriented storage.
For a column-oriented storage engine, a projection list indicating the
columns to be scanned may be necessary.  Is it possible to share this
information with current interface?

We realized that DDLs such as heap_create_with_catalog() are not
generalized.  Haribabu's latest patch that adds
SetNewFileNode_function() and CreateInitFort_function() is a step
towards this end.  However, the current API assumes that the storage
engine uses relation forks.  Isn't that too restrictive?

TupleDelete_function() accepts changingPart as a parameter to indicate
if this deletion is part of a movement from one partition to another.
Partitioning is a higher level abstraction as compared to storage.
Ideally, storage layer should have no knowledge of partitioning. The
tuple delete API should not accept any parameter related to
partitioning.

The API needs to be more accommodating towards block sizes used in
storage engines.  Currently, the same block size as heap seems to be
assumed, as evident from the type of some members of generic scan
object:

typedef struct TableScanDescData
{
  /* state set up at initscan time */
  BlockNumber rs_nblocks;     /* total number of blocks in rel */
  BlockNumber rs_startblock;  /* block # to start at */
  BlockNumber rs_numblocks;   /* max number of blocks to scan */
  /* rs_numblocks is usually InvalidBlockNumber, meaning "scan whole rel" */
  bool        rs_syncscan;    /* report location to syncscan logic? */
}           TableScanDescData;

Using bytes to represent this information would be more generic. E.g.
rs_startlocation as bytes/offset instead of rs_startblock and so on.

Asim

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.