perf: get base64 value for BYTES columns directly from protobuf value (GoogleCloudPlatform#3112)

Get the base64 string for BYTES columns directly from the unerlying protobuf value
when this is available.

Author: olavloite

src/main/java/com/google/cloud/spanner/pgadapter/parsers/BinaryParser.java

@@ -16,6 +16,7 @@
 
 import com.google.api.core.InternalApi;
 import com.google.cloud.ByteArray;
+import com.google.cloud.spanner.ProtobufResultSet;
 import com.google.cloud.spanner.ResultSet;
 import com.google.cloud.spanner.SpannerExceptionFactory;
 import com.google.cloud.spanner.Statement;
@@ -108,7 +109,7 @@ public static byte[] convertToPG(
       DataFormat format) {
     int bufferSize = sessionState.getBinaryConversionBufferSize();
     try {
-      String base64 = resultSet.getValue(position).getAsString();
+      String base64 = getBase64(resultSet, position);
       switch (format) {
         case SPANNER:
         case POSTGRESQL_BINARY:
@@ -128,7 +129,7 @@ public static byte[] convertToPG(
           }
           return null;
         case POSTGRESQL_TEXT:
-          return bytesToHex(resultSet.getBytes(position).toByteArray());
+          return bytesToHex(Base64.getDecoder().decode(base64));
         default:
           throw new IllegalArgumentException("unknown data format: " + format);
       }
@@ -137,6 +138,14 @@ public static byte[] convertToPG(
     }
   }
 
+  static String getBase64(ResultSet resultSet, int column) {
+    if (resultSet instanceof ProtobufResultSet
+        && ((ProtobufResultSet) resultSet).canGetProtobufValue(column)) {
+      return ((ProtobufResultSet) resultSet).getProtobufValue(column).getStringValue();
+    }
+    return resultSet.getValue(column).getAsString();
+  }
+
   static int copy(int length, InputStream from, DataOutputStream to, int bufferSize)
       throws IOException {
     byte[] buf = new byte[Math.min(length, bufferSize)];