Horton

Re: support for MERGE

Amit Langote <amitlangote09@gmail.com>

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From: Amit Langote <amitlangote09@gmail.com>
To: Álvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Daniel Westermann <dwe@dbi-services.com>, pgsql-hackers@lists.postgresql.org, Simon Riggs <simon.riggs@enterprisedb.com>, Pavan Deolasee <pavan.deolasee@gmail.com>
Date: 2021-11-14T11:45:15Z
Lists: pgsql-hackers 
On Sun, Nov 14, 2021 at 12:23 AM Álvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> On 2021-Nov-13, Daniel Westermann wrote:
> > /usr/bin/clang -Wno-ignored-attributes -fno-strict-aliasing -fwrapv -O2  -I../../../src/include  -D_GNU_SOURCE -I/usr/include/libxml2  -flto=thin -emit-llvm -c -o execMerge.bc execMerge.c
> > execMerge.c:552:32: warning: if statement has empty body [-Wempty-body]
> >                                         RELKIND_PARTITIONED_TABLE);
> >                                                                   ^
> > execMerge.c:552:32: note: put the semicolon on a separate line to silence this warning
>
> Oh wow, this may be a pretty serious problem actually.  I think it
> represents a gap in testing.  Thanks for reporting.

Ah, thanks indeed.  It seems that I fat-fingered that semicolon in.
Though, it's not as serious as it would've been if I had instead
fat-fingered a `&& false` into that condition and not the semicolon.
;)

The only problem caused by the code block that follows the buggy if
statement unconditionally executing is wasted cycles.  Fortunately,
there's no correctness issue, because rootRelInfo is the same as the
input result relation in the cases where the latter is not partitioned
and there'd be no map to convert the tuple, so the block is basically
a no-op.   I was afraid about the case where the input relation is a
regular inheritance parent, though apparently we don't support MERGE
in that case to begin with.

-- 
Amit Langote
EDB: http://www.enterprisedb.com

Commits

  1. Doc fixes for MERGE statement

  2. MERGE docs adjustments

  3. Link to MVCC docs in MERGE docs

  4. Fix EXPLAIN MERGE output when no tuples are processed

  5. Make EXPLAIN MERGE output format more compact

  6. Add support for MERGE SQL command

  7. Split ExecUpdate and ExecDelete into reusable pieces

  8. Add API of sorts for transition table handling in trigger.c

  9. Represent Lists as expansible arrays, not chains of cons-cells.