be/src/udf_samples/uda-sample.h

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#ifndef IMPALA_UDF_SAMPLE_UDA_H
#define IMPALA_UDF_SAMPLE_UDA_H

#include <udf/udf.h>

using namespace impala_udf;

/// This is an example of the COUNT aggregate function.
void CountInit(FunctionContext* context, BigIntVal* val);
void CountUpdate(FunctionContext* context, const IntVal& input, BigIntVal* val);
void CountMerge(FunctionContext* context, const BigIntVal& src, BigIntVal* dst);
BigIntVal CountFinalize(FunctionContext* context, const BigIntVal& val);

/// This is an example of the AVG(double) aggregate function. This function needs to
/// maintain two pieces of state, the current sum and the count. We do this using
/// the BufferVal intermediate type. When this UDA is registered, it would specify
/// 16 bytes (8 byte sum + 8 byte count) as the size for this buffer.
void AvgInit(FunctionContext* context, BufferVal* val);
void AvgUpdate(FunctionContext* context, const DoubleVal& input, BufferVal* val);
void AvgMerge(FunctionContext* context, const BufferVal& src, BufferVal* dst);
DoubleVal AvgFinalize(FunctionContext* context, const BufferVal& val);

/// This is a sample of implementing the STRING_CONCAT aggregate function.
/// Example: select string_concat(string_col, ",") from table
void StringConcatInit(FunctionContext* context, StringVal* val);
void StringConcatUpdate(FunctionContext* context, const StringVal& arg1,
    const StringVal& arg2, StringVal* val);
void StringConcatMerge(FunctionContext* context, const StringVal& src, StringVal* dst);
StringVal StringConcatFinalize(FunctionContext* context, const StringVal& val);

#endif