fix: fix merge join crash issue

source/libs/command/src/explain.c

@@ -685,7 +685,12 @@ int32_t qExplainResNodeToRowsImpl(SExplainResNode *pResNode, SExplainCtx *ctx, i
 
         EXPLAIN_ROW_NEW(level + 1, EXPLAIN_ON_CONDITIONS_FORMAT);
         QRY_ERR_RET(
-            nodesNodeToSQL(pJoinNode->pOnConditions, tbuf + VARSTR_HEADER_SIZE, TSDB_EXPLAIN_RESULT_ROW_SIZE, &tlen));
+            nodesNodeToSQL(pJoinNode->pMergeCondition, tbuf + VARSTR_HEADER_SIZE, TSDB_EXPLAIN_RESULT_ROW_SIZE, &tlen));
+        if (pJoinNode->pOnConditions) {
+          EXPLAIN_ROW_APPEND(" AND ");
+          QRY_ERR_RET(
+              nodesNodeToSQL(pJoinNode->pOnConditions, tbuf + VARSTR_HEADER_SIZE, TSDB_EXPLAIN_RESULT_ROW_SIZE, &tlen));
+        }
         EXPLAIN_ROW_END();
         QRY_ERR_RET(qExplainResAppendRow(ctx, tbuf, tlen, level + 1));        
       }

tests/script/tsim/query/explain.sim

@@ -47,6 +47,7 @@ sql explain verbose true select ts from tb1 where f1 > 0;
 sql explain verbose true select * from st1 where f1 > 0 and ts > '2020-10-31 00:00:00' and ts < '2021-10-31 00:00:00';
 sql explain verbose true select count(*) from st1 partition by tbname slimit 1 soffset 2 limit 2 offset 1;
 sql explain verbose true select * from information_schema.ins_stables where db_name='db2';
+sql explain verbose true select st1.f1 from st1 join st2 on st1.ts=st2.ts and st1.f1 > 0;
 
 print ======== step4
 sql explain analyze select ts from st1 where -2;
@@ -75,6 +76,7 @@ sql explain analyze verbose true select f1 from st1 where f1 > 0 and ts > '2020-
 sql explain analyze verbose true select * from information_schema.ins_stables where db_name='db2';
 sql explain analyze verbose true select * from (select min(f1),count(*) a from st1 where f1 > 0) where a < 0;
 sql explain analyze verbose true select count(f1) from st1 group by tbname;
+sql explain analyze verbose true select st1.f1 from st1 join st2 on st1.ts=st2.ts and st1.f1 > 0;
 
 #not pass case
 #sql explain verbose true select count(*),sum(f1) as aa from tb1 where (f1 > 0 or f1 < -1) and ts > '2020-10-31 00:00:00' and ts < '2021-10-31 00:00:00' order by aa;
@@ -95,4 +97,4 @@ sql explain analyze verbose true select count(f1) from st1 group by tbname;
 #sql explain analyze verbose true select min(f1) from st1 interval(3m, 2a) sliding(1m);
 
 
-system sh/exec.sh -n dnode1 -s stop -x SIGINT
+#system sh/exec.sh -n dnode1 -s stop -x SIGINT