The problem of SUM

[lhu]

hi,supersonic user group

I create a table t below:

i1 i2

1 1

And do the query:select sum(i2) from t where i1=0

Then i get a strange result,like -9958xxxx,a very big negative number.

What's the problem?

thx~

[Piotr Tabor]

Could you please write a unit test that demonstrates the problem ?

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[lhu]

void SumTest(Table& table) {

scoped_ptr<AggregationSpecification> specification(

new AggregationSpecification());

specification->AddAggregation(SUM, "i2", "i2");

const Expression* equal_i1 = Equal(ConstInt32(0),NamedAttribute("i1"));

scoped_ptr<Operation> filter1(Filter(equal_i1,

ProjectAllAttributes(),ScanView(table.view())));

scoped_ptr<Operation> aggregation(ScalarAggregate(specification.release(),filter1.release()));

scoped_ptr<Cursor> cursor(SucceedOrDie(aggregation->CreateCursor()));

ResultView result(cursor->Next(-1));

if(result.has_data() && !result.is_eos())

{

const int32* cnts = result.view().column(0).typed_data<INT32>();

cout << result.view().column(0).attribute().name() << ":" << *cnts << endl;

}

}

int main(int,char**)

{

TupleSchema schema;

schema.add_attribute(Attribute("i1",INT32,NOT_NULLABLE));

schema.add_attribute(Attribute("i2",INT32,NOT_NULLABLE));

Table table(schema,HeapBufferAllocator::Get());

TableRowWriter writer(&table);

writer.AddRow();

writer.Int32(1);

writer.Int32(1);

SumTest(table);

return 0;

}

在 2014年3月13日星期四UTC+8下午5时04分46秒，ptab写道：

Could you please write a unit test that demonstrates the problem ?

On Thu, Mar 13, 2014 at 9:53 AM, lhu <hulia...@gmail.com> wrote:

hi,supersonic user group

I create a table t below:

i1 i2

1 1

And do the query:select sum(i2) from t where i1=0

Then i get a strange result,like -9958xxxx,a very big negative number.

What's the problem?

thx~

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[Piotr Tabor]

1.  You are calling cursor->Next(-1). -1 is not a 'supported' constant. You should give here a small positive number, e.g. 1024. -1 it converted to uint64, so its probably a large constant and It can lead to OOMs. 

2. Please do checks result.view().row_count() whether it's >=1 before trying to read: result.view().column(0).typed_data<INT32>()[0]

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[lhu]

I tried your suggestions,but nothing changed.
在 2014年3月13日星期四UTC+8下午6时14分57秒，ptab写道：

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[lhu]

I also tried :

void SumTest(Table& table) {

scoped_ptr<AggregationSpecification> specification(

new AggregationSpecification());

specification->AddAggregation(SUM, "i2", "i2");

scoped_ptr<Operation> aggregation(ScalarAggregate(specification.release(),ScanView(table.view())));

scoped_ptr<Cursor> cursor(SucceedOrDie(aggregation->CreateCursor()));

ResultView result(cursor->Next(1024));

if(result.has_data() && !result.is_eos())

{

if(result.view().row_count() < 1)

{

cout << "ERROR" << endl;

return;

}

const int32* cnts = result.view().column(0).typed_data<INT32>();

cout << result.view().column(0).attribute().name() << ":" << *cnts << endl;

}

}

int main(int,char**)

{

TupleSchema schema;

schema.add_attribute(Attribute("i1",INT32,NOT_NULLABLE));

schema.add_attribute(Attribute("i2",INT32,NOT_NULLABLE));

Table table(schema,HeapBufferAllocator::Get());

SumTest(table);

return 0;

}

The result is a random number.

How can i solve this problem?

Thanks

在 2014年3月13日星期四UTC+8下午6时14分57秒，ptab写道：

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[Piotr Tabor]

Well, it seems that its a correct behavior. If the input list is empty, than the Scalar aggregate SUM(), MAX(), MIN(), AVG(), returns NULL for this column. 

The simplified testcase for your case is:

  TupleSchema schema;

  schema.add_attribute(Attribute("i1",INT32,NOT_NULLABLE));

  schema.add_attribute(Attribute("i2",INT32,NOT_NULLABLE));

  scoped_ptr<AggregationSpecification> specification(

    new AggregationSpecification());

  specification->AddAggregation(SUM, "i2", "i2");

  View view(schema);

  scoped_ptr<Operation> aggregation(

      ScalarAggregate(specification.release(), ScanView(view)));

  scoped_ptr<Cursor> cursor(SucceedOrDie(aggregation->CreateCursor()));

  ResultView result(cursor->Next(1024));

  CHECK(result.has_data());

  CHECK_EQ(1, result.view().row_count());

  EXPECT_TRUE(result.view().column(0).is_null()[0]);

  ResultView result2(cursor->Next(1024));

  CHECK(result2.is_eos());

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[lhu]

It's ok!

Thanks

在 2014年3月14日星期五UTC+8下午6时34分23秒，ptab写道：