TopN execute error when spill to disk happend

[EricZequan]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

tiup bench tpch --threads=50 --sf=10 prepare

set tidb_mem_quota_query=531837746;

select cast(l_extendedprice/2 as real) from lineitem order by cast(l_extendedprice/2 as real) asc limit 30000000;

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

no error

3. What did you see instead (Required)

Error 1105 (HY000): runtime error: index out of range [1] with length 1

4. What is your TiDB version? (Required)

master

[xzhangxian1008]

/severity major

[xzhangxian1008]

/remove-label may-affects-5.4

[EricZequan]

/remove-label may-affects-7.1

[EricZequan]

/remove-label may-affects-7.5

[EricZequan]

/remove-label may-affects-6.1

[EricZequan]

/remove-label may-affects-6.5

[EricZequan]

/remove-label may-affects-8.1

[EricZequan]

/remove-label may-affects-8.5