flaky test TestAlterAddConstraintStateChange3

[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)

     result.go:49: 
        	Error Trace:	pkg/testkit/result.go:49
        	            				pkg/ddl/constraint_test.go:247
        	Error:      	Not equal: 
        	            	expected: "[t CREATE TABLE `t` (\n  `a` int(11) DEFAULT NULL,\nCONSTRAINT `c3` CHECK ((`a` > 10))\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin]\n"
        	            	actual  : "[t CREATE TABLE `t` (\n  `a` int(11) DEFAULT NULL\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin]\n"
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -1,4 +1,3 @@
        	            	 [t CREATE TABLE `t` (
        	            	-  `a` int(11) DEFAULT NULL,
        	            	-CONSTRAINT `c3` CHECK ((`a` > 10))
        	            	+  `a` int(11) DEFAULT NULL
        	            	 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin]
        	Test:       	TestAlterAddConstraintStateChange3
        	Messages:   	sql:show create table t, args:[] 

https://tiprow.hawkingrei.com/view/gs/pingcapprow/pr-logs/pull/pingcap_tidb/48096/tiprow_fast_test/1719170692164882432#1:build-log.txt%3A2614

4. What is your TiDB version? (Required)

[CbcWestwolf]

/cc fzzf678

[jiyfhust]

I can make a pr to fix it.

[D3Hunter]

met it again in my branch, the reason is that we will enter OnJobUpdated twice for schema-state=public, once when job is in done and and once for synced state. if we start checking after first entrance, we might not see the correct schema as it might changed by the second entrance

    result.go:49: 
        	Error Trace:	pkg/testkit/result.go:49
        	            				pkg/ddl/constraint_test.go:244
        	Error:      	Not equal: 
        	            	expected: "[t CREATE TABLE `t` (\n  `a` int(11) DEFAULT NULL,\nCONSTRAINT `c3` CHECK ((`a` > 10))\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin]\n"
        	            	actual  : "[t CREATE TABLE `t` (\n  `a` int(11) DEFAULT NULL\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin]\n"
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -1,4 +1,3 @@
        	            	 [t CREATE TABLE `t` (
        	            	-  `a` int(11) DEFAULT NULL,
        	            	-CONSTRAINT `c3` CHECK ((`a` > 10))
        	            	+  `a` int(11) DEFAULT NULL
        	            	 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin]
        	Test:       	TestAlterAddConstraintStateChange3