Horton

Re: [PoC] Improve dead tuple storage for lazy vacuum

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: John Naylor <johncnaylorls@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>, Nathan Bossart <nathandbossart@gmail.com>, Andres Freund <andres@anarazel.de>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Yura Sokolov <y.sokolov@postgrespro.ru>
Date: 2024-03-14T01:53:14Z
Lists: pgsql-hackers 
On Thu, Mar 14, 2024 at 9:59 AM John Naylor <johncnaylorls@gmail.com> wrote:
>
> On Wed, Mar 13, 2024 at 9:29 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> > On Wed, Mar 13, 2024 at 8:05 PM John Naylor <johncnaylorls@gmail.com> wrote:
> > >
> > > On Wed, Mar 13, 2024 at 8:39 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > >
> > > > As I mentioned above, if we implement the test cases in C, we can use
> > > > the debug-build array in the test code. And we won't use it in AND/OR
> > > > operations tests in the future.
> > >
> > > That's a really interesting idea, so I went ahead and tried that for
> > > v71. This seems like a good basis for testing larger, randomized
> > > inputs, once we decide how best to hide that from the expected output.
> > > The tests use SQL functions do_set_block_offsets() and
> > > check_set_block_offsets(). The latter does two checks against a tid
> > > array, and replaces test_dump_tids().
> >
> > Great! I think that's a very good starter.
> >
> > The lookup_test() (and test_lookup_tids()) do also test that the
> > IsMember() function returns false as expected if the TID doesn't exist
> > in it, and probably we can do these tests in a C function too.
> >
> > BTW do we still want to test the tidstore by using a combination of
> > SQL functions? We might no longer need to input TIDs via a SQL
> > function.
>
> I'm not sure. I stopped short of doing that to get feedback on this
> much. One advantage with SQL functions is we can use generate_series
> to easily input lists of blocks with different numbers and strides,
> and array literals for offsets are a bit easier. What do you think?

While I'm not a fan of the following part, I agree that it makes sense
to use SQL functions for test data generation:

-- Constant values used in the tests.
\set maxblkno 4294967295
-- The maximum number of heap tuples (MaxHeapTuplesPerPage) in 8kB block is 291.
-- We use a higher number to test tidstore.
\set maxoffset 512

It would also be easier for developers to test the tidstore with their
own data set. So I agreed with the current approach; use SQL functions
for data generation and do the actual tests inside C functions. Is it
convenient for developers if we have functions like generate_tids()
and generate_random_tids() to generate TIDs so that they can pass them
to do_set_block_offsets()? Then they call check_set_block_offsets()
and others for actual data lookup and iteration tests.

Regards,

-- 
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com

Commits

  1. radixtree: Fix SIGSEGV at update of embeddable value to non-embeddable.

  2. Get rid of anonymous struct

  3. Teach radix tree to embed values at runtime

  4. Teach TID store to skip bitmap for small numbers of offsets

  5. Use bump context for TID bitmaps stored by vacuum

  6. Fix alignment of stack variable

  7. Use TidStore for dead tuple TIDs storage during lazy vacuum.

  8. Rethink create and attach APIs of shared TidStore.

  9. Fix inconsistent function prototypes with function definitions.

  10. Fix a calculation in TidStoreCreate().

  11. Fix potential integer handling issue in radixtree.h.

  12. Add TIDStore, to store sets of TIDs (ItemPointerData) efficiently.

  13. Fix link error for test_radixtree module on Windows

  14. Blind attempt to fix ODR violations

  15. Fix incorrect format specifier for int64

  16. Fix redefinition of typedefs

  17. Add template for adaptive radix tree

  18. Fix signedness error in 9f225e992 for gcc

  19. Introduce helper SIMD functions for small byte arrays

  20. Optimize vacuuming of relations with no indexes.

  21. Add bound check before bsearch() for performance

  22. Allocate consecutive blocks during parallel seqscans