sql: handle AOST in multi-stmt implicit txn

[rafiss]

fixes #85066

Release note (bug fix): Fixed a bug where the AS OF SYSTEM TIME clause was handled correctly in an implicit transaction that had multiple statements.

[cockroach-teamcity]

This change is 

[ZhouXing19]

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @rafiss and @Xiang-Gu)

---

pkg/sql/conn_executor_exec.go line 816 at r1 (raw file):

	// Implicit transactions can have multiple statements, so we need to check
	// if one has already been executed.
	if ex.implicitTxn() && !ex.extraTxnState.firstStmtExecuted {

Just to make sure I understand it correctly -- in this block, we set the planner's txn-state's timestamp with the one of the asof stmt, as we assume there's only one statement, which is the as of , running. We shouldn't do this if there're more than 1 stmts in the implicit txn.

Does it mean that if there're more than 1 statements, and the first one is an AS OF, it still should work?

If so, maybe we can add this case to the logic test as well?

[rafiss]

Yeah that is correct. That's a good idea for a test! I added it.

[ZhouXing19]

LGTM!

[rafiss]

bors r=ZhouXing19

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

---

error creating merge commit from 33c9c53 to blathers/backport-release-22.2-97063: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 22.2.x failed. See errors above.

---

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}