perf: vesselStaticSyncStep N+1 쿼리 제거 — DISTINCT ON bulk SELECT로 전환

이전: MMSI별 개별 SELECT (~10만 쿼리) → 수 분 소요
이후: DISTINCT ON (mmsi) 1회 bulk SELECT → 인메모리 CDC 비교

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/java/gc/mda/signal_batch/batch/job/VesselStaticStepConfig.java

@@ -54,6 +54,8 @@ public class VesselStaticStepConfig {
     public Step vesselStaticSyncStep() {
         return new StepBuilder("vesselStaticSyncStep", jobRepository)
                 .tasklet((contribution, chunkContext) -> {
+                    long stepStart = System.currentTimeMillis();
+
                     // 1. 캐시에서 전체 데이터 → MMSI별 그룹
                     Collection<AisTargetEntity> allEntities = cacheManager.getAllValues();
 
@@ -70,18 +72,16 @@ public class VesselStaticStepConfig {
                     Map<String, AisTargetEntity> coalesced = coalesceByMmsi(allEntities);
 
                     JdbcTemplate jdbcTemplate = new JdbcTemplate(queryDataSource);
+                    Timestamp hourBucketTs = Timestamp.valueOf(hourBucket);
 
-                    // 2. CDC: 이전 레코드와 비교 → 변경 시에만 INSERT
-                    String selectPrevSql = """
-                        SELECT imo, name, callsign, vessel_type, extra_info,
-                               length, width, draught, destination, status,
-                               signal_kind_code, class_type
-                        FROM signal.t_vessel_static
-                        WHERE mmsi = ? AND time_bucket <= ?
-                        ORDER BY time_bucket DESC
-                        LIMIT 1
-                    """;
+                    // 2. CDC: bulk SELECT로 이전 레코드 전체 조회 (N+1 → 1회)
+                    Map<String, Map<String, Object>> prevRecords = bulkFetchPreviousRecords(
+                            jdbcTemplate, hourBucketTs);
 
+                    log.info("t_vessel_static CDC 비교 시작 — 현재: {} 선박, 이전: {} 레코드",
+                            coalesced.size(), prevRecords.size());
+
+                    // 3. 인메모리 비교 → 변경 시에만 INSERT
                     String insertSql = """
                         INSERT INTO signal.t_vessel_static (
                             mmsi, time_bucket, imo, name, callsign,
@@ -104,26 +104,16 @@ public class VesselStaticStepConfig {
                             class_type = EXCLUDED.class_type
                     """;
 
-                    Timestamp hourBucketTs = Timestamp.valueOf(hourBucket);
                     int inserted = 0;
                     int skipped = 0;
-
                     List<Object[]> batchArgs = new ArrayList<>();
 
                     for (Map.Entry<String, AisTargetEntity> entry : coalesced.entrySet()) {
                         String mmsi = entry.getKey();
                         AisTargetEntity current = entry.getValue();
 
-                        // 이전 레코드 조회
-                        boolean changed;
-                        try {
-                            Map<String, Object> prev = jdbcTemplate.queryForMap(
-                                    selectPrevSql, mmsi, hourBucketTs);
-                            changed = hasStaticInfoChanged(current, prev);
-                        } catch (org.springframework.dao.EmptyResultDataAccessException e) {
-                            // 이전 레코드 없음 → 첫 INSERT
-                            changed = true;
-                        }
+                        Map<String, Object> prev = prevRecords.get(mmsi);
+                        boolean changed = (prev == null) || hasStaticInfoChanged(current, prev);
 
                         if (changed) {
                             Timestamp etaTs = current.getEta() != null
@@ -148,14 +138,52 @@ public class VesselStaticStepConfig {
                         jdbcTemplate.batchUpdate(insertSql, batchArgs);
                     }
 
-                    log.info("t_vessel_static 동기화 완료: 총 {} 선박, INSERT {} 건, CDC 스킵 {} 건",
-                            coalesced.size(), inserted, skipped);
+                    long elapsed = System.currentTimeMillis() - stepStart;
+                    log.info("t_vessel_static 동기화 완료: 총 {} 선박, INSERT {} 건, CDC 스킵 {} 건 ({}ms)",
+                            coalesced.size(), inserted, skipped, elapsed);
 
                     return org.springframework.batch.repeat.RepeatStatus.FINISHED;
                 }, transactionManager)
                 .build();
     }
 
+    /**
+     * DISTINCT ON (mmsi)로 전체 이전 레코드를 1회 bulk 조회
+     * N+1 개별 SELECT → 1회 bulk SELECT로 최적화
+     */
+    private Map<String, Map<String, Object>> bulkFetchPreviousRecords(
+            JdbcTemplate jdbcTemplate, Timestamp hourBucketTs) {
+        String sql = """
+            SELECT DISTINCT ON (mmsi)
+                   mmsi, imo, name, callsign, vessel_type, extra_info,
+                   length, width, draught, destination, status,
+                   signal_kind_code, class_type
+            FROM signal.t_vessel_static
+            WHERE time_bucket <= ?
+            ORDER BY mmsi, time_bucket DESC
+        """;
+
+        Map<String, Map<String, Object>> result = new HashMap<>();
+        jdbcTemplate.query(sql, rs -> {
+            Map<String, Object> row = new HashMap<>();
+            row.put("imo", rs.getObject("imo"));
+            row.put("name", rs.getString("name"));
+            row.put("callsign", rs.getString("callsign"));
+            row.put("vessel_type", rs.getString("vessel_type"));
+            row.put("extra_info", rs.getString("extra_info"));
+            row.put("length", rs.getObject("length"));
+            row.put("width", rs.getObject("width"));
+            row.put("draught", rs.getObject("draught"));
+            row.put("destination", rs.getString("destination"));
+            row.put("status", rs.getString("status"));
+            row.put("signal_kind_code", rs.getString("signal_kind_code"));
+            row.put("class_type", rs.getString("class_type"));
+            result.put(rs.getString("mmsi"), row);
+        }, hourBucketTs);
+
+        return result;
+    }
+
     /**
      * MMSI별 필드 COALESCE: 각 필드별 마지막 non-empty 값 조합
      */