LGTM, I only have nits. I'll defer to Marcus for approval though.

Reviewed 6 of 6 files at r1, all commit messages.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @mgartner and @Shivs11)

-- commits line 18 at r1:
nit: I'd omit the release note since now the behavior matches Postgres (in other words, we are "fixing" difference from PG that was introduced in previous PRs, but those PRs haven't been a part of any release, so we don't need a "bug fix" release note).

pkg/util/encoding/encoding.go line 111 at r1 (raw file):

	// Postgres currently has a special case (maybe a bug) where
	// the empty JSON Array sorts before all other JSON values.

nit: consider putting a link to the PG bug report here too.

pkg/util/encoding/encoding.go line 3477 at r1 (raw file):

// EncodeJSONArrayKeyMarker adds a JSON Array key encoding marker
// to buf and returns the new buffer.
func EncodeJSONArrayKeyMarker(buf []byte, dir Direction, length int64) []byte {

nit: perhaps s/length/arrayLength/g to be more explicit.

Reviewed 1 of 6 files at r1, 2 of 3 files at r3.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @Shivs11 and @yuzefovich)

-- commits line 18 at r1:

Done.

pkg/util/encoding/encoding.go line 111 at r1 (raw file):

Done.

pkg/util/encoding/encoding.go line 3477 at r1 (raw file):

Done.

pkg/util/json/encoded.go line 613 at r3 (raw file):

		return -1, nil
	}
	jDecoded, _ := j.decode()

Is it safe to ignore the error here? Probably not... I think we shouldn't decode the whole value either, just the marker to see if the array is empty.

@yuzefovich do you mind giving this another quick look? I did some refactoring.

Reviewed 2 of 6 files at r2, 1 of 3 files at r3, 2 of 2 files at r4, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @Shivs11)

pkg/util/json/encoded.go line 613 at r3 (raw file):

Oh, we don't even need to decode in these cases. Cool. Done.

Thanks!

Also perhaps consider updating the tech note too.

Reviewed 2 of 6 files at r2, 2 of 3 files at r3, 2 of 2 files at r4, 1 of 1 files at r5, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (and 1 stale) (waiting on @Shivs11)

-- commits line 18 at r1:

nit: also the PR description needs an update.

pkg/util/json/json_test.go line 80 at r5 (raw file):

		`false`,
		`true`,
		// In Postgres's sorting rules, the empty array comes before everything (even null),

nit: this comment should be updated.

Also perhaps consider updating the tech note too.

Done.

Reviewed 1 of 1 files at r5, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (and 1 stale) (waiting on @Shivs11)

-- commits line 18 at r1:

Done.