sql: do not print stack trace when logging if txn is not open

After executing each statement, that statement might be logged. If there
were any audit events, then we attempt to resolve the table names for
which the audit events have occurred. To do the resolution we're using
the current txn. Previously, if that txn has been aborted or committed,
it would result in a scary-looking stack trace added to the log, and
this commit fixes it.

Release note: None

pkg/sql/exec_log.go

@@ -30,6 +30,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/util/log/eventpb"
 	"github.com/cockroachdb/cockroach/pkg/util/log/logpb"
 	"github.com/cockroachdb/cockroach/pkg/util/timeutil"
+	"github.com/cockroachdb/errors"
 	"github.com/cockroachdb/redact"
 )
 
@@ -167,6 +168,8 @@ func (p *planner) maybeLogStatement(
 	p.maybeLogStatementInternal(ctx, execType, isCopy, numRetries, txnCounter, rows, err, queryReceived, hasAdminRoleCache, telemetryLoggingMetrics, stmtFingerprintID, queryStats)
 }
 
+var errTxnIsNotOpen = errors.New("txn is already committed or rolled back")
+
 func (p *planner) maybeLogStatementInternal(
 	ctx context.Context,
 	execType executorType,
@@ -323,13 +326,19 @@ func (p *planner) maybeLogStatementInternal(
 				mode = "rw"
 			}
 			tableName := ""
+			var tn *tree.TableName
 			// We only have a valid *table* name if the object being
 			// audited is table-like (includes view, sequence etc). For
 			// now, this is sufficient because the auditing feature can
 			// only audit tables. If/when the mechanisms are extended to
 			// audit databases and schema, we need more logic here to
 			// extract a name to include in the logging events.
-			tn, err := p.getQualifiedTableName(ctx, ev.desc)
+			if p.txn != nil && p.txn.IsOpen() {
+				// Only open txn accepts further commands.
+				tn, err = p.getQualifiedTableName(ctx, ev.desc)
+			} else {
+				err = errTxnIsNotOpen
+			}
 			if err != nil {
 				log.Warningf(ctx, "name for audited table ID %d not found: %v", ev.desc.GetID(), err)
 			} else {