Fix NPE while loading lookups from empty JDBC source (#16307)
diff --git a/extensions-core/lookups-cached-global/src/main/java/org/apache/druid/server/lookup/namespace/JdbcCacheGenerator.java b/extensions-core/lookups-cached-global/src/main/java/org/apache/druid/server/lookup/namespace/JdbcCacheGenerator.java
index f05ff70..ccf8504 100644
--- a/extensions-core/lookups-cached-global/src/main/java/org/apache/druid/server/lookup/namespace/JdbcCacheGenerator.java
+++ b/extensions-core/lookups-cached-global/src/main/java/org/apache/druid/server/lookup/namespace/JdbcCacheGenerator.java
@@ -204,18 +204,20 @@
if (tsColumn == null) {
return null;
}
- final Timestamp update = dbi.withHandle(
- handle -> {
- final String query = StringUtils.format(
- "SELECT MAX(%s) FROM %s",
- tsColumn, table
- );
- return handle
- .createQuery(query)
- .map(TimestampMapper.FIRST)
- .first();
- }
+ final String query = StringUtils.format(
+ "SELECT MAX(%s) FROM %s",
+ tsColumn, table
);
+ final Timestamp update = dbi.withHandle(
+ handle -> handle
+ .createQuery(query)
+ .map(TimestampMapper.FIRST)
+ .first()
+ );
+ if (update == null) {
+ LOG.info("Lookup table[%s] is empty. No rows returned for the query[%s].", table, query);
+ return null;
+ }
return update.getTime();
}
}
diff --git a/extensions-core/lookups-cached-global/src/test/java/org/apache/druid/server/lookup/namespace/NamespacedExtractorModuleTest.java b/extensions-core/lookups-cached-global/src/test/java/org/apache/druid/server/lookup/namespace/NamespacedExtractorModuleTest.java
index 715da7b..4e04f03 100644
--- a/extensions-core/lookups-cached-global/src/test/java/org/apache/druid/server/lookup/namespace/NamespacedExtractorModuleTest.java
+++ b/extensions-core/lookups-cached-global/src/test/java/org/apache/druid/server/lookup/namespace/NamespacedExtractorModuleTest.java
@@ -121,7 +121,7 @@
Assert.assertNotNull(version);
Map<String, String> map = cache.getCache();
Assert.assertEquals("bar", map.get("foo"));
- Assert.assertEquals(null, map.get("baz"));
+ Assert.assertNull(map.get("baz"));
}
@Test
diff --git a/extensions-core/lookups-cached-global/src/test/java/org/apache/druid/server/lookup/namespace/cache/JdbcExtractionNamespaceTest.java b/extensions-core/lookups-cached-global/src/test/java/org/apache/druid/server/lookup/namespace/cache/JdbcExtractionNamespaceTest.java
index cf71a5d..ada8e2e 100644
--- a/extensions-core/lookups-cached-global/src/test/java/org/apache/druid/server/lookup/namespace/cache/JdbcExtractionNamespaceTest.java
+++ b/extensions-core/lookups-cached-global/src/test/java/org/apache/druid/server/lookup/namespace/cache/JdbcExtractionNamespaceTest.java
@@ -391,6 +391,36 @@
}
@Test(timeout = 60_000L)
+ public void testEmptyTable()
+ throws InterruptedException
+ {
+ // Delete existing rows from table.
+ final Handle handle = derbyConnectorRule.getConnector().getDBI().open();
+ handle.createStatement(
+ StringUtils.format("DELETE FROM %s", TABLE_NAME)
+ ).setQueryTimeout(1).execute();
+
+ final JdbcExtractionNamespace extractionNamespace = new JdbcExtractionNamespace(
+ derbyConnectorRule.getMetadataConnectorConfig(),
+ TABLE_NAME,
+ KEY_NAME,
+ VAL_NAME,
+ tsColumn,
+ null,
+ new Period(0),
+ null,
+ 0,
+ null,
+ new JdbcAccessSecurityConfig()
+ );
+ try (CacheScheduler.Entry entry = scheduler.schedule(extractionNamespace)) {
+ CacheSchedulerTest.waitFor(entry);
+ final Map<String, String> map = entry.getCache();
+ Assert.assertTrue(map.isEmpty());
+ }
+ }
+
+ @Test(timeout = 60_000L)
public void testSkipOld()
throws InterruptedException
{
