nsivabalan commented on code in PR #18984:
URL: https://github.com/apache/hudi/pull/18984#discussion_r3616420755


##########
hudi-sync/hudi-hive-sync/src/main/java/org/apache/hudi/hive/HiveSyncConfigHolder.java:
##########
@@ -122,6 +122,23 @@ public class HiveSyncConfigHolder {
       .defaultValue(1000)
       .markAdvanced()
       .withDocumentation("The number of partitions one batch when synchronous 
partitions to hive.");
+  public static final ConfigProperty<Boolean> HIVE_SYNC_BATCHING_ENABLED = 
ConfigProperty
+      .key("hoodie.datasource.hive_sync.batching.enabled")
+      .defaultValue(false)
+      .markAdvanced()
+      .sinceVersion("1.1.0")

Review Comment:
   Fixed in the next push — both configs now use `sinceVersion("1.3.0")`.



##########
hudi-sync/hudi-hive-sync/src/main/java/org/apache/hudi/hive/HiveSyncConfigHolder.java:
##########
@@ -122,6 +122,23 @@ public class HiveSyncConfigHolder {
       .defaultValue(1000)
       .markAdvanced()
       .withDocumentation("The number of partitions one batch when synchronous 
partitions to hive.");
+  public static final ConfigProperty<Boolean> HIVE_SYNC_BATCHING_ENABLED = 
ConfigProperty
+      .key("hoodie.datasource.hive_sync.batching.enabled")
+      .defaultValue(false)
+      .markAdvanced()
+      .sinceVersion("1.1.0")
+      .withDocumentation("When true, partition operations 
(add/update/touch/drop) in the active sync mode "

Review Comment:
   Fixed in the next push. Reworked the `HIVE_SYNC_BATCHING_ENABLED` doc to 
scope precisely: HiveQL only, TOUCH is batched into `batch_num` chunks and 
dispatched in parallel, SET_LOCATION dispatched in parallel (one statement per 
partition), ADD-batching unchanged, DROP still serial, HMS/JDBC modes not 
affected. Also tightened the `HIVE_SYNC_BATCHING_THREADS` doc.



##########
hudi-sync/hudi-hive-sync/src/main/java/org/apache/hudi/hive/util/HiveDriverPool.java:
##########
@@ -0,0 +1,340 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hudi.hive.util;
+
+import org.apache.hudi.exception.HoodieException;
+import org.apache.hudi.hive.HiveSyncConfig;
+import org.apache.hudi.hive.HoodieHiveSyncException;
+
+import org.apache.hadoop.hive.conf.HiveConf;
+import org.apache.hadoop.hive.ql.Driver;
+import org.apache.hadoop.hive.ql.session.SessionState;
+import org.apache.hadoop.security.UserGroupInformation;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static 
org.apache.hudi.sync.common.HoodieSyncConfig.META_SYNC_DATABASE_NAME;
+
+/**
+ * Pool of Hive {@link Driver} + {@link SessionState} pairs for parallel 
HiveQL DDL.
+ *
+ * <p>Hive's {@code SessionState.start(state)} binds state to the calling 
thread's
+ * thread-local, and {@code Driver} reads from that thread-local during {@code 
run()}.
+ * A Driver constructed on one thread cannot be safely used from another. This 
pool
+ * solves that by giving each slot its own dedicated worker thread (a 
single-thread
+ * executor) — the Driver and SessionState are built on that thread by a 
bootstrap
+ * task, and all subsequent SQL for that slot runs on the same thread.
+ *
+ * <p><b>Usage contract:</b> use this pool only for partition-row DDL 
statements that
+ * are independent of each other and freely shuffleable across workers. 
Table-level
+ * statements (createTable, schema evolution, USE database) must continue to 
run on
+ * the session {@code Driver} held by {@code HiveQueryDDLExecutor} on the sync 
driver
+ * thread. The pool is gated behind {@code 
hoodie.datasource.hive_sync.batching.enabled}
+ * and is constructed only for HiveQL sync mode.
+ */
+public class HiveDriverPool implements AutoCloseable {
+
+  private static final Logger LOG = 
LoggerFactory.getLogger(HiveDriverPool.class);
+
+  // Per-worker Driver construction has to be fast in practice (a few hundred 
ms
+  // for the SessionState + Driver init). A 60s ceiling per worker leaves 
plenty of
+  // headroom for a slow JVM warm-up but bounds the failure mode if the 
metastore
+  // is unreachable or Hive hangs during init.
+  private static final long BOOTSTRAP_TIMEOUT_SECONDS = 60;
+
+  private final List<Worker> workers;
+  private final int size;
+  private volatile boolean closed;
+
+  public HiveDriverPool(HiveSyncConfig config, int size) {
+    this(config, size, new DefaultDriverFactory(config));
+  }
+
+  // Package-private for tests: accepts a DriverFactory so unit tests can 
inject
+  // mock Driver instances without standing up a real Hive instance.
+  HiveDriverPool(HiveSyncConfig config, int size, DriverFactory factory) {
+    if (size < 1) {
+      throw new IllegalArgumentException("Pool size must be >= 1, got " + 
size);
+    }
+    this.size = size;
+    this.workers = new ArrayList<>(size);
+    String databaseName = config.getStringOrDefault(META_SYNC_DATABASE_NAME);
+    PoolThreadFactory threadFactory = new PoolThreadFactory();
+    List<Future<Void>> bootstrapFutures = new ArrayList<>(size);
+    try {
+      for (int i = 0; i < size; i++) {
+        Worker worker = new Worker(threadFactory);
+        workers.add(worker);
+        bootstrapFutures.add(worker.executor.submit(() -> {
+          worker.driver = factory.newDriver(databaseName);
+          return null;
+        }));
+      }
+      // Block until all bootstraps complete so we surface construction errors
+      // before any caller hands us SQL. Bounded by BOOTSTRAP_TIMEOUT_SECONDS 
so a
+      // hung Hive init doesn't deadlock the sync driver thread.
+      for (Future<Void> f : bootstrapFutures) {
+        f.get(BOOTSTRAP_TIMEOUT_SECONDS, TimeUnit.SECONDS);
+      }
+    } catch (Exception e) {
+      tearDown();
+      throw new HoodieException("Failed to construct HiveDriverPool of size " 
+ size, e);
+    }
+    LOG.info("Initialized HiveDriverPool with {} workers", size);
+  }
+
+  /**
+   * Runs each given SQL on <i>every</i> worker, in order. Used for setup 
statements
+   * (e.g. {@code USE database}) that must establish per-thread session context
+   * before any partition statement runs. Blocks until all workers have 
completed
+   * the setup. Throws on first error.
+   */
+  public void runOnEachWorker(List<String> setupSqls) {
+    if (closed) {
+      throw new IllegalStateException("Cannot dispatch to a closed 
HiveDriverPool");
+    }
+    if (setupSqls.isEmpty()) {
+      return;
+    }
+    List<Future<?>> futures = new ArrayList<>(workers.size());
+    for (Worker worker : workers) {
+      futures.add(worker.executor.submit(() -> {
+        for (String sql : setupSqls) {
+          worker.driver.run(sql);
+        }
+        return null;
+      }));
+    }
+    awaitAll(futures);
+  }
+
+  /**
+   * Dispatches each SQL string to a worker (round-robin) and returns the list 
of
+   * futures. The caller is responsible for awaiting and collecting errors. 
SQL text
+   * is intentionally not logged per-statement here: batched TOUCH/ADD 
statements can
+   * be many kilobytes, and N parallel workers would multiply the log volume. 
See
+   * {@link #awaitAll(List)} for the per-call summary log.
+   */
+  public List<Future<?>> runAll(List<String> sqls) {

Review Comment:
   Renamed to `dispatchAll` in the next push (and updated the Javadoc to 
explicitly call out that it does not block — callers must `awaitAll`).



##########
hudi-sync/hudi-hive-sync/src/main/java/org/apache/hudi/hive/ddl/HiveQueryDDLExecutor.java:
##########
@@ -82,19 +95,61 @@ public void runSQL(String sql) {
     updateHiveSQLs(Collections.singletonList(sql));
   }
 
+  /**
+   * Partition-phase SQL fan-out. When the driver pool is present, any leading
+   * {@code USE database} statements are run on every worker (Hive 2.x's
+   * ALTER PARTITION SET LOCATION ignores db.table qualifiers and uses the
+   * connection's current database, so each worker needs to USE the right db
+   * before any partition ALTER). The remaining statements are then dispatched
+   * round-robin across the pool. Falls through to the sequential path on the
+   * session Driver when no pool is configured.
+   */
+  @Override
+  protected void runSQLs(List<String> sqls) {
+    if (sqls.isEmpty()) {
+      return;
+    }
+    if (!driverPool.isPresent()) {
+      updateHiveSQLs(sqls);
+      return;
+    }
+    HiveDriverPool pool = driverPool.get();
+    int firstNonUse = 0;
+    while (firstNonUse < sqls.size() && isUseStatement(sqls.get(firstNonUse))) 
{

Review Comment:
   Renamed `firstNonUse` → `useStatementCount` in the next push.



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