Added DISTINCT ON handling

[Hydrocharged]

This adds support for:

• Error: DISTINCT ON is not yet supported #2174

Related PRs:

• Added DISTINCT ON expressions vitess#446
• Added DISTINCT ON handling go-mysql-server#3369

[github-actions]

	Main	PR
covering_index_scan_postgres	538.10/s	540.06/s	+0.3%
index_join_postgres	113.67/s	116.61/s	+2.5%
index_join_scan_postgres	174.62/s	173.66/s	-0.6%
index_scan_postgres	11.07/s	11.02/s	-0.5%
oltp_point_select	2201.05/s	2214.75/s	+0.6%
oltp_read_only	1661.64/s	1648.32/s	-0.9%
select_random_points	104.33/s	102.01/s	-2.3%
select_random_ranges	414.80/s	395.59/s	-4.7%
table_scan_postgres	10.67/s	10.91/s	+2.2%
types_table_scan_postgres	4.94/s	4.96/s	+0.4%

[github-actions]

	Main	PR
Total	42090	42090
Successful	17514	17518
Failures	24576	24572
Partial Successes1	5587	5587

	Main	PR
Successful	41.6108%	41.6203%
Failures	58.3892%	58.3797%

${\color{lightgreen}Progressions (4)}$

subselect

QUERY: SELECT * FROM foo WHERE id IN
    (SELECT id2 FROM (SELECT DISTINCT ON (id2) id1, id2 FROM bar) AS s);

tsrf

QUERY: SELECT DISTINCT ON (a) a, b, generate_series(1,3) g
FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b)
ORDER BY a, b DESC;

QUERY: SELECT DISTINCT ON (a) a, b, generate_series(1,3) g
FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b)
ORDER BY a, b DESC, g DESC;

QUERY: SELECT DISTINCT ON (a, b, g) a, b, generate_series(1,3) g
FROM (VALUES (3, 2), (3,1), (1,1), (1,4), (5,3), (5,1)) AS t(a, b)
ORDER BY a, b DESC, g DESC;

Footnotes

1. These are tests that we're marking as Successful, however they do not match the expected output in some way. This is due to small differences, such as different wording on the error messages, or the column names being incorrect while the data itself is correct. ↩

[zachmu]

LGTM but see comments in GMS

[Hydrocharged]

Upon updating GMS to the newest version, I now need

• drop schema support #2172

to pass before I can merge as it changes interfaces. Once that's in, I'll merge with main then merge this in.