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Merged
merged 5 commits into from
Sep 14, 2025
Merged

Possible fix for #8734 #8735

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c6de939
Possible fix for #8734
aafemt Sep 8, 2025
38da83d
Use explicit pool
aafemt Sep 8, 2025
df1717b
Use HalfStaticArray as demanded
aafemt Sep 9, 2025
f727114
Use begin() instead of getBuffer()
aafemt Sep 10, 2025
70eaf53
Combine conditions as requested
aafemt Sep 13, 2025
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27 changes: 18 additions & 9 deletions src/dsql/DsqlRequests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -596,19 +596,28 @@ void DsqlDmlRequest::doExecute(thread_db* tdbb, jrd_tra** traHandle,

// if this is a singleton select that return some data, make sure there's in fact one record

if (singleton && (request->req_flags & req_active) && outMsgLength > 0)
if (singleton)
{
// Create a temp message buffer and try one more receive.
// If it succeed then the next record exists.
if (outMsgLength > 0)
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@hvlad hvlad Sep 13, 2025

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I don't understand why there is check for outMsgLength > 0 - is it possible to be false when singleton == true ?
Even if out message with zero length is possible (???), what should happens for the singleton && outMsgLength == 0 case ?
This place is very unclear for me.
In v5 there was just check for singleton == true, btw

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@aafemt aafemt Sep 13, 2025

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Just in case. If the function was called with outMetadata == nullptr - just assume success. The difference from v5 is that buffers here are provided by application rather than of engine itself.

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@hvlad hvlad Sep 13, 2025

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Is it possible to have singleton == true && outMetadata == nullptr ?
In any case, why two nested if here ?

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@aafemt aafemt Sep 13, 2025

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Initially check for request's activity was out of inner if. Then I realized that some BLR code can intentionally run to the end without entering blr_send and an application aware of it can provide no output buffer.

If you are sure that I'm wrong feel free to change this piece later.

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@hvlad hvlad Sep 13, 2025

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I'm sure that this code is not clear. And you changed it this way.
Formally,

if (a) {
  if (b) {
...
  }
}

is the same as

if (a && b) {
...
}

thus I ask why you choose first one. If there is no real reason, change it.
If there is a reasons - provide it, and put in comments to avoid similar misunderstanding for the future readers.

{
// No record returned though expected
if (!(request->req_flags & req_active))
{
status_exception::raise(Arg::Gds(isc_stream_eof));
}

std::unique_ptr<UCHAR[]> message_buffer(new UCHAR[outMsgLength]);
// Create a temp message buffer and try one more receive.
// If it succeed then the next record exists.

JRD_receive(tdbb, request, message->msg_number, outMsgLength, message_buffer.get());
HalfStaticArray<UCHAR, BUFFER_SMALL> message_buffer(getPool(), outMsgLength);

// Still active request means that second record exists
if ((request->req_flags & req_active))
{
status_exception::raise(Arg::Gds(isc_sing_select_err));
JRD_receive(tdbb, request, message->msg_number, outMsgLength, message_buffer.getBuffer(outMsgLength, false));

// Still active request means that second record exists
if ((request->req_flags & req_active))
{
status_exception::raise(Arg::Gds(isc_sing_select_err));
}
}
}
}
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