sql: fix tracing of postqueries

When we're performing tracing, we derive a special `consumeCtx` when
creating a DistSQLReceiver for the whole plan. That context should be
used for all components of the physical plan (main query, sub- and
post-queries), and the span needs to be finished by calling the stored
`cleanup` function. Previously, this was called in `ProducerDone` of the
main query which resulted in the span being finished before the
post-queries are run. As a result, the tracing spans for cascades and
checks could be incomplete.

This commit fixes the problem by delaying the finish of the span until
the DistSQLReceiver is released (since it is a convenient place that all
callers of `MakeDistSQLReceiver` call in a deferred invocation).

Release justification: bug fix.

Release note (bug fix): Previously, the traces of cascades and checks
could be incomplete, and now it is fixed.

pkg/sql/distsql_running.go

@@ -434,7 +434,9 @@ type DistSQLReceiver struct {
 
 	rangeCache *rangecache.RangeCache
 	tracing    *SessionTracing
-	cleanup    func()
+	// cleanup will be called when the DistSQLReceiver is Release()'d back to
+	// its sync.Pool.
+	cleanup func()
 
 	// The transaction in which the flow producing data for this
 	// receiver runs. The DistSQLReceiver updates the transaction in
@@ -572,6 +574,7 @@ func MakeDistSQLReceiver(
 
 // Release releases this DistSQLReceiver back to the pool.
 func (r *DistSQLReceiver) Release() {
+	r.cleanup()
 	*r = DistSQLReceiver{}
 	receiverSyncPool.Put(r)
 }
@@ -782,7 +785,6 @@ func (r *DistSQLReceiver) ProducerDone() {
 		panic("double close")
 	}
 	r.closed = true
-	r.cleanup()
 }
 
 // Types is part of the RowReceiver interface.

pkg/sql/opt/exec/execbuilder/testdata/autocommit_nonmetamorphic

@@ -668,6 +668,7 @@ WHERE message       LIKE '%r$rangeid: sending batch%'
 ----
 dist sender send  r36: sending batch 1 DelRng to (n1,s1):1
 dist sender send  r36: sending batch 2 CPut to (n1,s1):1
+dist sender send  r36: sending batch 2 Scan to (n1,s1):1
 dist sender send  r36: sending batch 1 EndTxn to (n1,s1):1
 
 query B
@@ -692,6 +693,7 @@ WHERE message       LIKE '%r$rangeid: sending batch%'
 dist sender send  r36: sending batch 1 DelRng to (n1,s1):1
 dist sender send  r36: sending batch 1 Scan to (n1,s1):1
 dist sender send  r36: sending batch 1 Put to (n1,s1):1
+dist sender send  r36: sending batch 1 Scan to (n1,s1):1
 dist sender send  r36: sending batch 1 EndTxn to (n1,s1):1
 
 query B
@@ -717,6 +719,7 @@ WHERE message       LIKE '%r$rangeid: sending batch%'
 dist sender send  r36: sending batch 1 DelRng to (n1,s1):1
 dist sender send  r36: sending batch 1 Scan to (n1,s1):1
 dist sender send  r36: sending batch 1 Del to (n1,s1):1
+dist sender send  r36: sending batch 1 Scan to (n1,s1):1
 dist sender send  r36: sending batch 1 EndTxn to (n1,s1):1
 
 # Test with a single cascade, which should use autocommit.
@@ -743,6 +746,7 @@ WHERE message       LIKE '%r$rangeid: sending batch%'
 ----
 dist sender send  r36: sending batch 1 DelRng to (n1,s1):1
 dist sender send  r36: sending batch 1 DelRng to (n1,s1):1
+dist sender send  r36: sending batch 1 Scan to (n1,s1):1
 dist sender send  r36: sending batch 1 Del, 1 EndTxn to (n1,s1):1
 
 # -----------------------

pkg/sql/opt/exec/execbuilder/testdata/partial_index_nonmetamorphic

@@ -905,6 +905,7 @@ query T kvtrace
 DELETE FROM t57085_p WHERE p = 1;
 ----
 DelRange /Table/56/1/1 - /Table/56/1/1/#
+Scan /Table/57/{1-2}
 Del /Table/57/2/1/10/0
 Del /Table/57/1/10/0
 Del /Table/57/1/20/0