sql: use IndexFetchSpec for zigzag join

[RaduBerinde]

rowexec: follow-up cleanup for EncodedKey in zigzagjoiner

The zig-zag joiner code still uses Bytes instead of EncodedKey for
the encoded key. This works because the fixed values are encoded using
VALUE encoding, and the value encodings are the same for DBytes and
DEncodedKey.

This commit updates the zigzag joiner to use the correct EncodedKey
type. The code no longer needs to special case inverted indexes -
with the addition of support for EncodedKey in keyside.Encode, the
general code path can now be used.

Release note: None

sql: clean up ZigZagJoinerSpec

This change cleans up the zig-zag joiner spec: we move the per-side
information into a Side sub-message and use a list of Sides instead of
many parallel lists. Other misc cleanup in the zigzag joiner code is
included.

Release note: None

sql: use IndexFetchSpec for zigzag join

This commit changes the zigzag joiner to use IndexFetchSpec for the
two sides instead of table and index descriptors. The internal schema
of the zigzag joiner is changed to match the fetched columns,
simplifying the execution code.

This change necessitates fixes on the planning side - we weren't
determining the necessary scan columns correctly (this wasn't a
problem when the internal schema had all table columns and we were
relying on the execution layer to figure out what is needed).

Release note: None

[cockroach-teamcity]

This change is 

[yuzefovich]

Very nice cleanup!

Reviewed 2 of 2 files at r1, 5 of 5 files at r2, 27 of 27 files at r3, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @mgartner and @RaduBerinde)

---

pkg/sql/rowexec/zigzagjoiner_test.go, line 232 at r3 (raw file):

					},
					{
						FetchSpec: makeFetchSpec(t, empty, "d", "a,b,d"),

This should be highRangeDesc.

---

pkg/sql/rowexec/zigzagjoiner_test.go, line 248 at r3 (raw file):

				Sides: []execinfrapb.ZigzagJoinerSpec_Side{
					{
						FetchSpec: makeFetchSpec(t, empty, "c", "a,b,c"),

Here the order of empty and highRangeDesc is switched.

[mgartner]

🤩

Reviewed 2 of 2 files at r1, 5 of 5 files at r2, 27 of 27 files at r3, all commit messages.
Reviewable status: complete! 2 of 0 LGTMs obtained (waiting on @RaduBerinde)

[RaduBerinde]

TFTRs!

Reviewable status: complete! 2 of 0 LGTMs obtained (waiting on @yuzefovich)

---

pkg/sql/rowexec/zigzagjoiner_test.go, line 232 at r3 (raw file):

Previously, yuzefovich (Yahor Yuzefovich) wrote…

This should be highRangeDesc.

Done.

---

pkg/sql/rowexec/zigzagjoiner_test.go, line 248 at r3 (raw file):

Previously, yuzefovich (Yahor Yuzefovich) wrote…

Here the order of empty and highRangeDesc is switched.

Done.

[RaduBerinde]

bors r+

[craig]

Build succeeded:

• GitHub CI (Cockroach)