add comments

Signed-off-by: birdstorm <samuelwyf@hotmail.com>

src/main/java/org/tikv/raw/RawKVClient.java

@@ -99,6 +99,7 @@ public class RawKVClient implements AutoCloseable {
    * @param values values
    */
   public void batchPut(BackOffer backOffer, List<ByteString> keys, List<ByteString> values) {
+    assert keys.size() == values.size();
     Map<ByteString, ByteString> keysToValues = mapKeysToValues(keys, values);
     Map<Long, List<ByteString>> groupKeys = groupKeysByRegion(keys);
     keys.clear();
@@ -112,45 +113,7 @@ public class RawKVClient implements AutoCloseable {
           entry.getValue().stream().map(keysToValues::get).collect(Collectors.toList()),
           RAW_BATCH_PUT_SIZE);
     }
-
+    sendBatchPut(backOffer, batches);
-    for (Batch batch : batches) {
-      completionService.submit(
-          () -> {
-            Pair<TiRegion, Metapb.Store> pair =
-                regionManager.getRegionStorePairByRegionId(batch.regionId);
-            RegionStoreClient client = RegionStoreClient.create(pair.first, pair.second, session);
-            List<Kvrpcpb.KvPair> kvPairs = new ArrayList<>();
-            for (int i = 0; i < batch.keys.size(); i++) {
-              kvPairs.add(
-                  Kvrpcpb.KvPair.newBuilder()
-                      .setKey(batch.keys.get(i))
-                      .setValue(batch.values.get(i))
-                      .build());
-            }
-            try {
-              client.rawBatchPut(backOffer, kvPairs);
-            } catch (final TiKVException e) {
-              // TODO: any elegant way to re-split the ranges if fails?
-              backOffer.doBackOff(BackOffFunction.BackOffFuncType.BoRegionMiss, e);
-              logger.warn("ReSplitting ranges for BatchPutRequest");
-              // recursive calls
-              batchPut(backOffer, batch.keys, batch.values);
-            }
-            return null;
-          });
-    }
-    try {
-      for (int i = 0; i < batches.size(); i++) {
-        completionService.take().get(BackOffer.rawkvMaxBackoff, TimeUnit.SECONDS);
-      }
-    } catch (InterruptedException e) {
-      Thread.currentThread().interrupt();
-      throw new TiKVException("Current thread interrupted.", e);
-    } catch (TimeoutException e) {
-      throw new TiKVException("TimeOut Exceeded for current operation. ", e);
-    } catch (ExecutionException e) {
-      throw new TiKVException("Execution exception met.", e);
-    }
   }
 
   /**
@@ -238,6 +201,15 @@ public class RawKVClient implements AutoCloseable {
     }
   }
 
+  /**
+   * Append batch to list and split them according to batch limit
+   *
+   * @param batches a grouped batch
+   * @param regionId region ID
+   * @param keys keys
+   * @param values values
+   * @param limit batch max limit
+   */
   private void appendBatches(
       List<Batch> batches,
       long regionId,
@@ -260,6 +232,12 @@ public class RawKVClient implements AutoCloseable {
     }
   }
 
+  /**
+   * Group by list of keys according to its region
+   *
+   * @param keys keys
+   * @return a mapping of keys and their regionId
+   */
   private Map<Long, List<ByteString>> groupKeysByRegion(List<ByteString> keys) {
     Map<Long, List<ByteString>> groups = new HashMap<>();
     TiRegion lastRegion = null;
@@ -281,6 +259,53 @@ public class RawKVClient implements AutoCloseable {
     return map;
   }
 
+  /**
+   * Send batchPut request concurrently
+   *
+   * @param backOffer current backOffer
+   * @param batches list of batch to send
+   */
+  private void sendBatchPut(BackOffer backOffer, List<Batch> batches) {
+    for (Batch batch : batches) {
+      completionService.submit(
+          () -> {
+            Pair<TiRegion, Metapb.Store> pair =
+                regionManager.getRegionStorePairByRegionId(batch.regionId);
+            RegionStoreClient client = RegionStoreClient.create(pair.first, pair.second, session);
+            List<Kvrpcpb.KvPair> kvPairs = new ArrayList<>();
+            for (int i = 0; i < batch.keys.size(); i++) {
+              kvPairs.add(
+                  Kvrpcpb.KvPair.newBuilder()
+                      .setKey(batch.keys.get(i))
+                      .setValue(batch.values.get(i))
+                      .build());
+            }
+            try {
+              client.rawBatchPut(backOffer, kvPairs);
+            } catch (final TiKVException e) {
+              // TODO: any elegant way to re-split the ranges if fails?
+              backOffer.doBackOff(BackOffFunction.BackOffFuncType.BoRegionMiss, e);
+              logger.warn("ReSplitting ranges for BatchPutRequest");
+              // recursive calls
+              batchPut(backOffer, batch.keys, batch.values);
+            }
+            return null;
+          });
+    }
+    try {
+      for (int i = 0; i < batches.size(); i++) {
+        completionService.take().get(BackOffer.rawkvMaxBackoff, TimeUnit.SECONDS);
+      }
+    } catch (InterruptedException e) {
+      Thread.currentThread().interrupt();
+      throw new TiKVException("Current thread interrupted.", e);
+    } catch (TimeoutException e) {
+      throw new TiKVException("TimeOut Exceeded for current operation. ", e);
+    } catch (ExecutionException e) {
+      throw new TiKVException("Execution exception met.", e);
+    }
+  }
+
   private Iterator<Kvrpcpb.KvPair> rawScanIterator(ByteString startKey, ByteString endKey) {
     return new RawScanIterator(startKey, endKey, Integer.MAX_VALUE, session);
   }