Summary: There was a big performance hit induced when removing consecutive nodes from the concurrent list. The reason why it was happening is that the iterator has a pointer to previous node, and uses that pointer to re-link the whole list after the deletion. That node wasn't alive because it was deleted earlier and was always being updated to the next deleted entry in the list while incrementing the iterator. This behaviour caused find_and_disconnect method to be invoked, which has an O(n) complexity. That made our removal of O(n) entries from the list run in O(n^2) time, which is obviously slow.
Reviewers: buda, mislav.bradac, florijan
Reviewed By: mislav.bradac
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D483
Summary:
A lot of style changes. Major content changes are the following:
- Bolt and "interface" stuff moved to quick-start (not so quick anymore?)
- removed the "Memgraph is 100% Bolt compliant" and client-compatiblity claims because they are probably not true and aren't necessary
- moved "Limitations" to the bottom
- Python quickstart - moved explanations into the code, moved DB cleanup to the end (natural data flow)
What still needs work in my opion:
- the table in the "Limitations" part renders horribly (no space between cells)
- heading3 and heading4 are rendered the same in the "QuickStart", which is bad in the "Limitations" section
- I only went through the "Installation" and part of the "QuickStart", still a lot to go
Reviewers: buda, dtomicevic, florijan
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D473
Summary:
benchmark/query/stripped.cpp outputs garbage because of some race
condition in logger. Sometime even crashes, just be sure this
should be removed.
Reviewers: buda
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D477
Summary:
There were a couple of issues with handling the above 2 signals.
1) Calling `std::exit` from a signal handler is undefined behaviour.
The only defined way for a signal handler to stop the program is calling
one of: `std::_Exit`, `std::abort` or `std::quick_exit`. Neither of them
will completely clean the resources, so a clean exit is not possible.
Since SIGSEGV and SIGABRT happen in extraordinary circumstances that we
wish to debug 99% of the time, it makes sense to generate a core dump
which can be inspected by a debugger. Of the 3 termination functions,
only `std::abort` will generate a core dump, so it makes sense to use
that to stop the program.
Also, since we are now aborting as is the default behaviour on SIGSEGV
and SIGABRT, it becomes questionable why have a custom handler at all.
2) Raising an exception inside a signal handler is undefined behaviour
Although the handler by itself does not raise an exception, it is
possible for the logging facility to raise one. This is a real case when
logging a stack trace in particular. Stack trace is generated by
creating a string "<function name> <line location>". It is possible that
a function name will contain '{}' somewhere inside. This is usually the
case with anonymous functions. The generated string is then passed to
logging, which uses the `fmt` library to fill '{}' with remaining
arguments. Since only a single argument (the stack trace string) is
passed for formatting, naturally the `fmt::format` throws an exception,
that it is missing a format argument.
We could provide an overload which takes a single string, but that
defeats the purpose of `fmt::format` raising an exception in regular
code if we forget to pass an argument. Another solution is to escape the
whole stack trace string, so it is valid for formatting, but this only
complicates the handler even further. The simplest solution is to send
the stack trace to `stderr` and avoid logging altogether.
Simplify Shutdown, so it can be used in a signal handler
Reviewers: florijan, mferencevic, buda, mislav.bradac
Reviewed By: mferencevic, buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D474
Summary:
Since assertions should signify an abnormal program condition, it makes
sense for them to call `std::abort`. This way, we'll get a core dump
which can be inspected in a debugger.
Update utils/assert.hpp documentation
Reviewers: florijan, buda, mislav.bradac
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D475
Summary: An unpleasant race-condition detected. Solution proposed. It's not very pretty. Perhaps consider using the ConcurrentPushQueue. Not 100% sure, but it should make the GC code easier to work with.
Reviewers: buda, mislav.bradac, teon.banek, dgleich
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D469
Summary:
Remove utils/stacktrace/log.hpp
The single function defined in log.hpp is used only in
memgraph_bolt.cpp. Therefore, the function has been moved and the file
removed.
Move utils/stacktrace/stacktrace.hpp one level up
Move some logging from memgraph_bolt to Server
Reviewers: buda, dtomicevic
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D465
Summary:
There's no need to see the results of tests, since we are only running
ctest to generate code coverage reports.
Reviewers: buda
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D461
Summary:
This is an obvious bug, caused by an oversight. A test has been added
for this case.
Reviewers: florijan, mislav.bradac, buda
Reviewed By: florijan
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D455
Summary: Bipartite stress test. Common methods useful in the process of testing with python Bolt driver.
Reviewers: mislav.bradac, florijan
Reviewed By: florijan
Subscribers: florijan, pullbot, buda
Differential Revision: https://phabricator.memgraph.io/D423
Summary:
- GC changed to evaluate old records w.r.t. the oldest transaction's id AND snapshot, as opposed to only id
- MVCC hints exp+aborted race condition prevented
- minor MVCC refactors and cleanups
- minor Transaction refactors and cleanups
Reviewers: buda, dgleich
Reviewed By: buda, dgleich
Subscribers: dtomicevic, pullbot
Differential Revision: https://phabricator.memgraph.io/D434
Summary:
Do some minor corrections to openCypher docs
Add links to Bolt drivers in our documentation
Reviewers: florijan, buda, mferencevic, dtomicevic
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D440
Summary: Alpha package scripts. Alpha version is going to be shipped within docker.
Reviewers: teon.banek, mferencevic
Reviewed By: teon.banek
Subscribers: pullbot, buda
Differential Revision: https://phabricator.memgraph.io/D436
Summary:
CMake is smart enough to transitively detect dependencies and link them
appropriately. Therefore, it is enough that we put all libraries that
memgraph uses to the dependency list of memgraph_lib and memgraph_pic
targets.
Patch the fmt library for C++14 and higher
fmt library would detect that C++11 is supported and then put the
compiler flag. This flag was set so it overrides parent project compiler
flags. This override from fmt would prevent us from using C++14
features. New version (3.1) of fmt resolves this issue, but it hasn't
been released yet. Therefore, this commit updates the script which
clones fmt to use the released 3.0.1 version and apply the fix on that.
Reviewers: dgleich, buda
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D441
Summary:
This is a basic overview of various supported features of openCypher in
Memgraph. A lot of the documentation refers to Neo4j manual. This needs to
change in the future.
Reviewers: buda, dtomicevic, mislav.bradac, florijan
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D439
