Support "COPY FROM/TO PROGRAM '...' WITH (format parquet)"

[aykut-bozkurt]

Now it is possible to use programs with COPY table TO/FROM PROGRAM '...' WITH (format parquet) syntax.

e.g.

pg_parquet=# CREATE TABLE test_table(a int);
CREATE TABLE

pg_parquet=# INSERT INTO test_table SELECT i FROM generate_series(1,10) i;
INSERT 0 10

pg_parquet=# COPY test_table TO PROGRAM 'cat > /tmp/test.parquet' WITH (format parquet);
COPY 10

pg_parquet=# COPY test_table FROM PROGRAM 'cat /tmp/test.parquet' WITH (format parquet);
COPY 10

Similar to how we support COPY TO/FROM stdin/stdout WITH(format parquet), we use a temp file as intermediate file and finally we copy from/to program's stdout/stdin by piping the temp file.

Closes #147.

[codecov]

Codecov Report

❌ Patch coverage is 97.05882% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.03%. Comparing base (0d80fcd) to head (36bf1c8).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/pgrx_tests/copy_program.rs	96.77%	7 Missing ⚠️
src/arrow_parquet/uri_utils.rs	95.65%	2 Missing ⚠️
src/parquet_copy_hook/copy_to_program.rs	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #146      +/-   ##
==========================================
+ Coverage   90.84%   91.03%   +0.18%     
==========================================
  Files          92       95       +3     
  Lines       10442    10759     +317     
==========================================
+ Hits         9486     9794     +308     
- Misses        956      965       +9     

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[sfc-gh-mslot]

when would you have stdin + program?

[aykut-bozkurt]

it is fine (we use tmp file as intermediate step for both stdio and program) let me rename it to reduce confusion.

[sfc-gh-mslot]

can we use the same functions that COPY uses?

[pgguru]

Looks pretty good overall; one q, mainly to fill in some of my Rust gaps.

[pgguru]

I'm not great at Rust, so there may be some semantic misunderstanding here, but how does this differ from .expect(), just no access to the underlying value for the message?

[aykut-bozkurt]

std::io::copy returns Result. We want to extract error to also print it via unwrap_or_else. We cannot do that with expect.