flaky test TestIndexJoin31494

[hawkingrei]

Bug Report

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1. Minimal reproduce step (Required)

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

3. What did you see instead (Required)

     executor_issue_test.go:342: 
        	Error Trace:	pkg/executor/test/issuetest/executor_issue_test.go:342
        	Error:      	Should be true
        	Test:       	TestIndexJoin31494 

https://tiprow.hawkingrei.com/view/gs/pingcapprow/pr-logs/pull/pingcap_tidb/57511/fast_test_tiprow/1858821745377546240#1:build-log.txt%3A11024

4. What is your TiDB version? (Required)

[hawkingrei]

https://tiprow.hawkingrei.com/view/gs/pingcapprow/pr-logs/pull/pingcap_tidb/58507/fast_test_tiprow/1871594597516316672#1:build-log.txt%3A3452