Expose session ID to clients

[georgebuckerfield]

This change exposes the ID of a session to clients in two ways:

• as a session variable (session_id)
• as a column in SHOW QUERIES

e.g.

root@:26257/defaultdb> show session_id;
             session_id             
+----------------------------------+
  15cded2b6282789c0000000000000001  
(1 row)

Time: 3.6358ms

root@:26257/defaultdb> show queries;
              query_id             | node_id |            session_id            | user_name |              start               |        query         | client_address  | application_name | distributed |   phase    
+----------------------------------+---------+----------------------------------+-----------+----------------------------------+----------------------+-----------------+------------------+-------------+-----------+
  15cdefea7e589d3c0000000000000001 |       1 | 15cded2b6282789c0000000000000001 | root      | 2019-10-15 21:40:35.442981+00:00 | SHOW CLUSTER QUERIES | 127.0.0.1:39450 | $ cockroach sql  |    false    | executing  
(1 row)

Time: 25.2691ms

Fixes #32055

Release note: None

[cockroach-teamcity]

This change is 

[jordanlewis]

Hey @georgebuckerfield so sorry about the delay here.

[solongordon]

Thanks for the contribution! Couple minor things but generally looks great. Please rebase and squash your commits. And just to match our conventions, please update the commit subject to sql: expose session ID to clients.

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @georgebuckerfield, @rohany, and @solongordon)

---

pkg/sql/crdb_internal.go, line 903 at r1 (raw file):

			clusterSessionID := BytesToClusterWideID(session.ID)
			sessionID = tree.NewDString(clusterSessionID.String())
		}

It looks like this logic is now duplicated with populateSessionsTable. Could you pull this out into a function?

---

pkg/sql/planner.go, line 41 at r3 (raw file):

	tree.EvalContext

	sessionID *ClusterWideID

FYI I believe this was just added for other reasons, so you can just rebase and use the existing field.

[georgebuckerfield]

Thanks for the review @solongordon! I think it should be ready for another look now - let me know if there are any other changes you'd like.

[solongordon]

I'm just going to add a release note to your commit message to notify our docs team of the change.

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @georgebuckerfield and @rohany)

[solongordon]

bors r+

[craig]

Build succeeded

• GitHub CI (Cockroach)