[vepadulano]

RNTupleProcessor::GetNEntries is called (at the moment) by RNTupleProcessorDS. This commit proposes to not keep the page sources after having opened them, but to only get the number of entries and then close them. This avoids the issue in
datasource_ntuple_processor.cxx test "error: Too many files open", seen on the Windows CI and visible also on a UNIX system by calling 'ulimit -n' with a number lower than the number of files of the chain in the test (1000).

[github-actions]

Test Results

    24 files      24 suites   4d 0h 18m 29s ⏱️
 3 883 tests  3 883 ✅ 0 💤 0 ❌
83 646 runs  83 646 ✅ 0 💤 0 ❌

Results for commit 8771300.

♻️ This comment has been updated with latest results.

[vepadulano]

Stopped CI runs to avoid overloading runners before the rc, will re-run afterwards.

[vepadulano]

Just to show that on my Fedora node I see:

• before this change

$: ulimit -n 256
$: /datasource_ntuple_processor --gtest_filter=RNTupleProcessorDSTest.Chain
Running main() from /builddir/build/BUILD/gtest-1.17.0-build/googletest-1.17.0/googletest/src/gtest_main.cc
Note: Google Test filter = RNTupleProcessorDSTest.Chain
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from RNTupleProcessorDSTest
[ RUN      ] RNTupleProcessorDSTest.Chain
unknown file: Failure
C++ exception with description "Cannot open 'RNTupleProcessorDS_test.root', error: Too many open files" thrown in the test body.

• after this change

$: ulimit -n 256
$: ./datasource_ntuple_processor --gtest_filter=RNTupleProcessorDSTest.Chain
Running main() from /builddir/build/BUILD/gtest-1.17.0-build/googletest-1.17.0/googletest/src/gtest_main.cc
Note: Google Test filter = RNTupleProcessorDSTest.Chain
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from RNTupleProcessorDSTest
[ RUN      ] RNTupleProcessorDSTest.Chain
[       OK ] RNTupleProcessorDSTest.Chain (3394 ms)
[----------] 1 test from RNTupleProcessorDSTest (3394 ms total)

[enirolf]

Thank you!

[vepadulano]

/backport to 6.42