<fix>[ai]: use Json_getKeyValue for MySQL 5.5 compat

use Json_getKeyValue from beforeMigrate.sql to replace
JSON_EXTRACT which requires MySQL 5.7+, and change
endTime column type from TIMESTAMP to DATETIME.

Resolves: ZSTAC-72079

Change-Id: I50f05f114eae474f94f1046811dc0a8734b88c42

Author: Shangmin Dou

conf/db/upgrade/V5.5.12__schema.sql

@@ -6,27 +6,28 @@ CALL CREATE_INDEX('GpuDeviceSpecVO', 'idx_gpu_spec_normalized_model', 'normalize
 -- Previously these values were only stored inside the opaque JSON TEXT field,
 -- making them invisible to ZQL ORDER BY queries.
 CALL ADD_COLUMN('ModelEvaluationTaskVO', 'totalScore', 'DOUBLE', 1, NULL);
-CALL ADD_COLUMN('ModelEvaluationTaskVO', 'endTime', 'TIMESTAMP', 1, '1970-01-02 00:00:00');
+CALL ADD_COLUMN('ModelEvaluationTaskVO', 'endTime', 'DATETIME', 1, NULL);
 
 -- Add indexes to support efficient sorting
 CALL CREATE_INDEX('ModelEvaluationTaskVO', 'idx_ModelEvaluationTaskVO_totalScore', 'totalScore');
 CALL CREATE_INDEX('ModelEvaluationTaskVO', 'idx_ModelEvaluationTaskVO_endTime', 'endTime');
 
 -- Backfill totalScore from opaque JSON for existing completed tasks
+-- Uses Json_getKeyValue defined in beforeMigrate.sql for MySQL 5.5+ compatibility
 UPDATE `zstack`.`ModelEvaluationTaskVO`
-SET `totalScore` = JSON_EXTRACT(`opaque`, '$.details.total_score')
+SET `totalScore` = CAST(Json_getKeyValue(`opaque`, 'total_score') AS DECIMAL(20,6))
 WHERE `opaque` IS NOT NULL
   AND `totalScore` IS NULL
-  AND JSON_EXTRACT(`opaque`, '$.details.total_score') IS NOT NULL;
+  AND Json_getKeyValue(`opaque`, 'total_score') IS NOT NULL;
 
 -- Backfill endTime from opaque JSON for existing completed/failed tasks
 -- end_time format from Python agent: "MMM dd, yyyy hh:mm:ss a" (e.g. "Jan 01, 2025 10:30:00 AM")
 UPDATE `zstack`.`ModelEvaluationTaskVO`
 SET `endTime` = STR_TO_DATE(
-    JSON_UNQUOTE(JSON_EXTRACT(`opaque`, '$.details.end_time')),
+    Json_getKeyValue(`opaque`, 'end_time'),
     '%b %d, %Y %h:%i:%s %p'
 )
 WHERE `opaque` IS NOT NULL
   AND `endTime` IS NULL
-  AND JSON_EXTRACT(`opaque`, '$.details.end_time') IS NOT NULL
-  AND JSON_UNQUOTE(JSON_EXTRACT(`opaque`, '$.details.end_time')) != '';
+  AND Json_getKeyValue(`opaque`, 'end_time') IS NOT NULL
+  AND Json_getKeyValue(`opaque`, 'end_time') != '';