runtime stats get lost if the index merge partial task return 0 row

[time-and-fate]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table t(a int, b int , c int, d int, e int,index ia(a), index ib(b), index ic(c), index idd(d), index ie(e));
explain analyze select * from t where a = 10 or b = 30 or c = 10 or d = 1 or e = 90;

2. What did you expect to see? (Required)

The "time" of "execution info" of IndexRangeScan is not 0.

3. What did you see instead (Required)

explain analyze select * from t where a = 10 or b = 30 or c = 10 or d = 1 or e = 90;
+--------------------------------+---------+---------+-----------+-----------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------+-----------+------+
| id                             | estRows | actRows | task      | access object         | execution info                                                                                                                                                    | operator info                                 | memory    | disk |
+--------------------------------+---------+---------+-----------+-----------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------+-----------+------+
| IndexMerge_14                  | 0.04    | 0       | root      |                       | time:1.4ms, loops:1,                                                                                                                                              |                                               | 498 Bytes | N/A  |
| ├─IndexRangeScan_8(Build)      | 0.01    | 0       | cop[tikv] | table:t, index:ia(a)  | time:0s, loops:0, cop_task: {num: 1, max: 483.8µs, proc_keys: 0, rpc_num: 1, rpc_time: 370.8µs, copr_cache_hit_ratio: 0.00}, tikv_task:{time:312.2µs, loops:0}    | range:[10,10], keep order:false, stats:pseudo | N/A       | N/A  |
| ├─IndexRangeScan_9(Build)      | 0.01    | 0       | cop[tikv] | table:t, index:ib(b)  | time:0s, loops:0, cop_task: {num: 1, max: 658.7µs, proc_keys: 0, rpc_num: 1, rpc_time: 520.7µs, copr_cache_hit_ratio: 0.00}, tikv_task:{time:456.9µs, loops:0}    | range:[30,30], keep order:false, stats:pseudo | N/A       | N/A  |
| ├─IndexRangeScan_10(Build)     | 0.01    | 0       | cop[tikv] | table:t, index:ic(c)  | time:0s, loops:0, cop_task: {num: 1, max: 617µs, proc_keys: 0, rpc_num: 1, rpc_time: 516.3µs, copr_cache_hit_ratio: 0.00}, tikv_task:{time:446.3µs, loops:0}      | range:[10,10], keep order:false, stats:pseudo | N/A       | N/A  |
| ├─IndexRangeScan_11(Build)     | 0.01    | 0       | cop[tikv] | table:t, index:idd(d) | time:0s, loops:0, cop_task: {num: 1, max: 441.8µs, proc_keys: 0, rpc_num: 1, rpc_time: 356.8µs, copr_cache_hit_ratio: 0.00}, tikv_task:{time:304.7µs, loops:0}    | range:[1,1], keep order:false, stats:pseudo   | N/A       | N/A  |
| ├─IndexRangeScan_12(Build)     | 0.01    | 0       | cop[tikv] | table:t, index:ie(e)  | time:0s, loops:0, cop_task: {num: 1, max: 531.6µs, proc_keys: 0, rpc_num: 1, rpc_time: 435.3µs, copr_cache_hit_ratio: 0.00}, tikv_task:{time:369.7µs, loops:0}    | range:[90,90], keep order:false, stats:pseudo | N/A       | N/A  |
| └─TableRowIDScan_13(Probe)     | 0.04    | 0       | cop[tikv] | table:t               |                                                                                                                                                                   | keep order:false, stats:pseudo                | N/A       | N/A  |
+--------------------------------+---------+---------+-----------+-----------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------+-----------+------+

4. What is your TiDB version? (Required)

master