Andrew Peter Marlow created AVRO-4134:
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Summary: Specific.hh decode and adding a large number of items to
a vector without using reserve first
Key: AVRO-4134
URL: https://issues.apache.org/jira/browse/AVRO-4134
Project: Apache Avro
Issue Type: Improvement
Components: c++
Affects Versions: 1.12.0
Reporter: Andrew Peter Marlow
There is an improvement that could be made to the c++ avro decoder for large
arrays. In Specific.hh the code loops over a collection, performing a push_back
for each item. This is in the static decode template function. It does a clear
and then does a push back for each item that it adds. So when the collection is
large, hundreds or even thousands of items, the repeated expansion of the
vector can cause a performance issue. The fix is simple. Right after the call
to clear, make a call to reserve. The number of items may have to be counted
with code like this:
size_t count = 0;
for (size_t n = d.arrayStart(); n != 0; n = d.arrayNext()) {
++count;
}
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