be/src/runtime/collection-value.h

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//   http://www.apache.org/licenses/LICENSE-2.0
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#ifndef IMPALA_RUNTIME_COLLECTION_VALUE_H
#define IMPALA_RUNTIME_COLLECTION_VALUE_H

#include "runtime/descriptors.h"

namespace impala {

/// The in-memory representation of a collection-type slot. Note that both arrays and maps
/// are represented in memory as arrays of tuples. After being read from the on-disk data,
/// arrays and maps are effectively indistinguishable; a map can be thought of as an array
/// of key/value structs (and neither of these fields are necessarily materialized in the
/// item tuples).
struct __attribute__((__packed__)) CollectionValue {
  /// Pointer to buffer containing item tuples.
  uint8_t* ptr;

  /// The number of item tuples.
  int num_tuples;

  CollectionValue() : ptr(NULL), num_tuples(0) {}

  /// Returns the size of this collection in bytes, i.e. the number of bytes written to
  /// ptr.
  inline int64_t ByteSize(const TupleDescriptor& item_tuple_desc) const {
    return static_cast<int64_t>(num_tuples) * item_tuple_desc.byte_size();
  }

  /// For C++/IR interop, we need to be able to look up types by name.
  static const char* LLVM_CLASS_NAME;
};

}

#endif