feat: improve json stream writer json to proto conversion speed by

caching the schema. This will introduce approximately 2x improvement to
append speed

google-cloud-bigquerystorage/clirr-ignored-differences.xml

@@ -157,5 +157,10 @@
     <className>com/google/cloud/bigquery/storage/v1/JsonStreamWriter</className>
     <method>boolean isDone()</method>
   </difference>
+  <difference>
+    <differenceType>7012</differenceType>
+    <className>com/google/cloud/bigquery/storage/v1/ToProtoConverter</className>
+    <method>java.util.List convertToProtoMessage(com.google.protobuf.Descriptors$Descriptor, com.google.cloud.bigquery.storage.v1.TableSchema, java.lang.Iterable, boolean)</method>
+  </difference>
 </differences>
 

google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/Exceptions.java

@@ -259,6 +259,29 @@ public AppendSerializationError(
     }
   }
 
+  /** This exception is thrown from proto converter to wrap the row index to error mapping. */
+  static class RowIndexToErrorException extends IllegalArgumentException {
+    Map<Integer, String> rowIndexToErrorMessage;
+
+    boolean hasDataUnknownError;
+
+    public RowIndexToErrorException(
+        Map<Integer, String> rowIndexToErrorMessage, boolean hasDataUnknownError) {
+      this.rowIndexToErrorMessage = rowIndexToErrorMessage;
+      this.hasDataUnknownError = hasDataUnknownError;
+    }
+
+    // This message should not be exposed to the user directly.
+    // Please examine individual row's error through `rowIndexToErrorMessage`.
+    public String getMessage() {
+      return "The map of row index to error message is " + rowIndexToErrorMessage.toString();
+    }
+
+    public boolean hasDataUnknownError() {
+      return hasDataUnknownError;
+    }
+  }
+
   /** This exception is used internally to handle field level parsing errors. */
   public static class FieldParseError extends IllegalArgumentException {
     private final String fieldName;