diff --git a/xuqm-bugcollect-service/src/main/resources/db/migration/V6__build_id.sql b/xuqm-bugcollect-service/src/main/resources/db/migration/V6__build_id.sql
index e7c10e2..96fe2e1 100644
--- a/xuqm-bugcollect-service/src/main/resources/db/migration/V6__build_id.sql
+++ b/xuqm-bugcollect-service/src/main/resources/db/migration/V6__build_id.sql
@@ -1,27 +1,55 @@
 -- V6: build_id support for multi-build-per-version sourcemap tracking
--- ─────────────────────────────────────────────────────────────────────
--- log_sourcemaps:
---   • Drop old unique key that prevented multiple builds of the same version
---   • Add build_id (nullable for backward compat with pre-V6 uploads)
---   • New unique key includes build_id; MySQL treats NULL as distinct in UNIQUE,
---     so old rows (build_id=NULL) are not affected and remain individually unique
---   • Add fallback index for version-only lookup (for events without buildId)
---
--- log_issue_events:
---   • Add build_id so events can be matched to the exact sourcemap build
+-- log_sourcemaps: add build_id, update unique key, add fallback index
+-- log_issue_events: add build_id for exact symbolication matching
 
-ALTER TABLE log_sourcemaps
-    ADD COLUMN build_id VARCHAR(32) NULL COMMENT 'Gradle build timestamp yyyyMMddHHmmss; NULL = pre-V6 upload'
-    AFTER bundle_name;
+-- Conditional: add build_id to log_sourcemaps only if not exists
+SET @col_exists = (
+    SELECT COUNT(*) FROM information_schema.COLUMNS
+    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'log_sourcemaps' AND COLUMN_NAME = 'build_id'
+);
+SET @sql = IF(@col_exists = 0,
+    'ALTER TABLE log_sourcemaps ADD COLUMN build_id VARCHAR(32) NULL COMMENT ''Gradle build timestamp yyyyMMddHHmmss; NULL = pre-V6 upload'' AFTER bundle_name',
+    'SELECT 1'
+);
+PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;
 
-ALTER TABLE log_sourcemaps DROP KEY uk_map;
+-- Conditional: drop old uk_map key only if still exists
+SET @key_exists = (
+    SELECT COUNT(*) FROM information_schema.STATISTICS
+    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'log_sourcemaps' AND INDEX_NAME = 'uk_map'
+);
+SET @sql = IF(@key_exists > 0, 'ALTER TABLE log_sourcemaps DROP KEY uk_map', 'SELECT 1');
+PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;
 
-ALTER TABLE log_sourcemaps
-    ADD UNIQUE KEY uk_map_build (app_key, platform, app_version, build_id, bundle_name);
+-- Conditional: add uk_map_build unique key only if not exists
+SET @key_exists = (
+    SELECT COUNT(*) FROM information_schema.STATISTICS
+    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'log_sourcemaps' AND INDEX_NAME = 'uk_map_build'
+);
+SET @sql = IF(@key_exists = 0,
+    'ALTER TABLE log_sourcemaps ADD UNIQUE KEY uk_map_build (app_key, platform, app_version, build_id, bundle_name)',
+    'SELECT 1'
+);
+PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;
 
-ALTER TABLE log_sourcemaps
-    ADD INDEX idx_sm_version_latest (app_key, platform, app_version, bundle_name, uploaded_at);
+-- Conditional: add idx_sm_version_latest only if not exists
+SET @key_exists = (
+    SELECT COUNT(*) FROM information_schema.STATISTICS
+    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'log_sourcemaps' AND INDEX_NAME = 'idx_sm_version_latest'
+);
+SET @sql = IF(@key_exists = 0,
+    'ALTER TABLE log_sourcemaps ADD INDEX idx_sm_version_latest (app_key, platform, app_version, bundle_name, uploaded_at)',
+    'SELECT 1'
+);
+PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;
 
-ALTER TABLE log_issue_events
-    ADD COLUMN build_id VARCHAR(32) NULL COMMENT 'Matches log_sourcemaps.build_id for exact symbolication'
-    AFTER release;
+-- Conditional: add build_id to log_issue_events only if not exists
+SET @col_exists = (
+    SELECT COUNT(*) FROM information_schema.COLUMNS
+    WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'log_issue_events' AND COLUMN_NAME = 'build_id'
+);
+SET @sql = IF(@col_exists = 0,
+    'ALTER TABLE log_issue_events ADD COLUMN build_id VARCHAR(32) NULL COMMENT ''Matches log_sourcemaps.build_id for exact symbolication'' AFTER app_version',
+    'SELECT 1'
+);
+PREPARE stmt FROM @sql; EXECUTE stmt; DEALLOCATE PREPARE stmt;