unstable test TestHypoIndexDDL

[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)

--- FAIL: TestHypoIndexDDL (1.12s)
    result.go:49:
                Error Trace:    testkit/result.go:49
                                                        planner/core/plan_test.go:970
                Error:          Not equal:
                                expected: "[t CREATE TABLE `t` (\n  `a` int(11) DEFAULT NULL,\n  `b` int(11) DEFAULT NULL,\n  `c` int(11) DEFAULT NULL,\n  `d` int(11) DEFAULT NULL,\n  KEY `a` (`a`),\n  KEY `hypo_a` (`a`) /* HYPO INDEX */,\n  KEY `hypo_bc` (`b`,`c`) /* HYPO INDEX */\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin]\n"
                                actual  : "[t CREATE TABLE `t` (\n  `a` int(11) DEFAULT NULL,\n  `b` int(11) DEFAULT NULL,\n  `c` int(11) DEFAULT NULL,\n  `d` int(11) DEFAULT NULL,\n  KEY `a` (`a`),\n  KEY `hypo_bc` (`b`,`c`) /* HYPO INDEX */,\n  KEY `hypo_a` (`a`) /* HYPO INDEX */\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin]\n"

                                Diff:
                                --- Expected
                                +++ Actual
                                @@ -6,4 +6,4 @@
                                   KEY `a` (`a`),
                                -  KEY `hypo_a` (`a`) /* HYPO INDEX */,
                                -  KEY `hypo_bc` (`b`,`c`) /* HYPO INDEX */
                                +  KEY `hypo_bc` (`b`,`c`) /* HYPO INDEX */,
                                +  KEY `hypo_a` (`a`) /* HYPO INDEX */
                                 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin]
                Test:           TestHypoIndexDDL
                Messages:       sql:show create table t, args:[]

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