feat: reading data from hstore columns

[cbrachem]

Here's the PR announced in #436. @staticlibs would you mind checking it out?

Does this PR need an accompanying PR for the docs? As of right now, this extension mostly contains functionality that's needed for the actual communication with Postgres. My PR ist just two string conversion functions. Maybe a "misc" section at the bottom of the docs page, or a section that lists "QOL" functions that are not direcly related to postgres connectivity?

[cbrachem]

need to downgrade because I've been using c++17 stuff

[cbrachem]

Integration tests say the function postgres_hstore_get does not exist:

1. test/sql/misc/postgres_hstore.test:18
================================================================================
Query unexpectedly failed (test/sql/misc/postgres_hstore.test:18)
 (test/sql/misc/postgres_hstore.test:18)!
================================================================================
SELECT postgres_hstore_get('a=>b', 'a');
================================================================================
Actual result:
================================================================================
Catalog Error: Scalar Function with name postgres_hstore_get does not exist!
Did you mean "list_reverse_sort"?

Yet when I download the extension from this build run and load it into a DuckDB instance, it looks like it's working:

memory D load '~/Downloads/postgres_scanner.duckdb_extension';
memory D select postgres_hstore_get('a=>b', 'a');
┌──────────────────────────────────┐
│ postgres_hstore_get('a=>b', 'a') │
│             varchar              │
├──────────────────────────────────┤
│ b                                │
└──────────────────────────────────┘

Why doesn't it load the functions during integration tests? What am I missing? @staticlibs Do you have an idea?

[staticlibs]

Why doesn't it load the functions during integration tests? What am I missing? @staticlibs Do you have an idea?

Unittester has some peculiar logic for loading the extension listed in require. As a workaround you can run the ATTACH before calling a function or add the following after the requires:

statement ok
PRAGMA enable_verification

[cbrachem]

Unittester has some peculiar logic for loading the extension listed in require. As a workaround you can run the ATTACH before calling a function or add the following after the requires:

statement ok
PRAGMA enable_verification

I already have the pragma line in postgres_hstore.test, right after require postgres_scanner. I have noticed that the postgres_binary_read_*.test test files state LOAD postgres_scanner; after the require. On my machine, that did the trick. Now fingers crossed that it also works in CI.

[staticlibs]

Thanks for the PR! Looks good to me.

[cbrachem]

Thanks for the PR! Looks good to me.

Thanks for your quick review. Please let me know if I should prepare a PR for the documentation.

[staticlibs]

Please let me know if I should prepare a PR for the documentation.

Yes, this won't harm, just I myself won't be able to review it.