Revert "pre-allocate buf in gandiva for variable len vector (apache#99)"

This reverts commit 179eff6.

Author: zhouyuan

cpp/src/arrow/util/compression_zlib_isal.cc

@@ -375,6 +375,7 @@ class GZipCodec : public Codec {
       ret = isal_inflate(&state_);
       if (ret == ISAL_BLOCK_FINISH || ret == ISAL_DECOMP_OK) break;
 
+      printf("AAA");
       // Failure, buffer was too small
       return Status::IOError("Too small a buffer passed to GZipCodec. InputLength=",
                              input_length, " OutputLength=", output_buffer_length);

cpp/src/gandiva/cache.cc

@@ -20,7 +20,7 @@
 
 namespace gandiva {
 
-static const int DEFAULT_CACHE_SIZE = 2000;
+static const int DEFAULT_CACHE_SIZE = 500;
 
 int GetCapacity() {
   int capacity;

cpp/src/gandiva/jni/jni_common.cc

@@ -848,10 +848,8 @@ Java_org_apache_arrow_gandiva_evaluator_JniWrapper_evaluateProjector(
               "null");
           break;
         }
-        auto buf = std::make_shared<JavaResizableBuffer>(env, jexpander,
-          output_vector_idx, value_buf, data_sz);
-        buf->Resize(3970*16, false);
-        buffers.push_back(buf);
+        buffers.push_back(std::make_shared<JavaResizableBuffer>(
+            env, jexpander, output_vector_idx, value_buf, data_sz));
       } else {
         buffers.push_back(std::make_shared<arrow::MutableBuffer>(value_buf, data_sz));
       }

cpp/src/gandiva/projector.cc

@@ -291,7 +291,7 @@ Status Projector::AllocArrayData(const DataTypePtr& type, int64_t num_records,
     data_len = arrow::BitUtil::BytesForBits(num_records * fw_type.bit_width());
   } else if (arrow::is_binary_like(type_id)) {
     // we don't know the expected size for varlen output vectors.
-    data_len = 3970 * 8;
+    data_len = 0;
   } else {
     return Status::Invalid("Unsupported output data type " + type->ToString());
   }