Commit aab6b0ee27 introduced the
controversial new IMR format, which relied on a very template-heavy
infrastructure to generate serialization and deserialization code via
template meta-programming. The promise was that this new format, beyond
solving the problems the previous open-coded representation had (working
on linearized buffers), will speed up migrating other components to this
IMR format, as the IMR infrastructure reduces code bloat, makes the code
more readable via declarative type descriptions as well as safer.
However, the results were almost the opposite. The template
meta-programming used by the IMR infrastructure proved very hard to
understand. Developers don't want to read or modify it. Maintainers
don't want to see it being used anywhere else. In short, nobody wants to
touch it.
This commit does a conceptual revert of
aab6b0ee27. A verbatim revert is not
possible because related code evolved a lot since the merge. Also, going
back to the previous code would mean we regress as we'd revert the move
to fragmented buffers. So this revert is only conceptual, it changes the
underlying infrastructure back to the previous open-coded one, but keeps
the fragmented buffers, as well as the interface of the related
components (to the extent possible).
Fixes: #5578
Merged patch series by Konstantin Osipov:
"These series improve uniqueness of generated timeuuids and change
list append/prepend logic to use client/LWT timestamp in timeuuids
generated for list keys. Timeuuid compare functions are
optimized.
The test coverage is extended for all of the above."
uuid: add a comment warning against UUID::operator<
uuid: replace slow versions of timeuiid compare with optimized/tested versions.
test: add tests for legacy uuid compare & msb monotonicity
test: add a test case for append/prepend limit
test: add a test case for monotonicity of timeuuid least significant bits
uuid: implement optimized timeuuid compare
test: add a test case for list prepend/append with custom timestamp
lists: rewrite list prepend to use append machinery
lists: use query timestamp for list cell values during append
uuid: fill in UUID node identifier part of UUID
test: add a CQL test for list append/prepend operations
The keys classes (partition_key et al) already use managed_bytes,
but they assume the data is not fragmented and make liberal use
of that by casting to bytes_view. The view classes use bytes_view.
Change that to managed_bytes_view, and adjust return values
to managed_bytes/managed_bytes_view.
The callers are adjusted. In some places linearization (to_bytes())
is needed, but this isn't too bad as keys are always <= 64k and thus
will not be fragmented when out of LSA. We can remove this
linearization later.
The serialize_value() template is called from a long chain, and
can be reached with either bytes_view or managed_bytes_view.
Rather than trace and adjust all the callers, we patch it now
with constexpr if.
operator bytes_view (in keys) is converted to operator
managed_bytes_view, allowing callers to defer or avoid
linearization.
A sequel to #7692.
This series gets rid of linearization when validating collections and tuple types. (Other types were already validated without linearizing).
The necessary helpers for reading from fragmented buffers were introduced in #7692. All this series does is put them to use in `validate()`.
Refs: #6138Closes#7770
* github.com:scylladb/scylla:
types: add single-fragment optimization in validate()
utils: fragment_range: add with_simplified()
cql3: statements: select_statement: remove unnecessary use of with_linearized
cql3: maps: remove unnecessary use of with_linearized
cql3: lists: remove unnecessary use of with_linearized
cql3: tuples: remove unnecessary use of with_linearized
cql3: sets: remove unnecessary use of with_linearized
cql3: tuples: remove unnecessary use of with_linearized
cql3: attributes: remove unnecessary uses of with_linearized
types: validate lists without linearizing
types: validate tuples without linearizing
types: validate sets without linearizing
types: validate maps without linearizing
types: template abstract_type::validate on FragmentedView
types: validate_visitor: transition from FragmentRange to FragmentedView
utils: fragmented_temporary_buffer: add empty() to FragmentedView
utils: fragmented_temporary_buffer: don't add to null pointer
Manipulating fragmented views is costlier that manipulating contiguous views,
so let's detect the common situation when the fragmented view is actually
contiguous underneath, and make use of that.
Note: this optimization is only useful for big types. For trivial types,
validation usually only checks the size of the view.
This is primarily a stylistic change. It makes the interface more consistent
with deserialize(). It will also allow us to call `validate()` for collection
elements in `validate_aux()`.
This will allow us to easily get rid of linearizations when validating
collections and tuples, because the helpers used in validate_aux() already
have FragmentedView overloads.
Values usually come in a single fragment, but we pay the cost of fragmented
deserialization nevertheless: bigger view objects (4 words instead of 2 words)
more state to keep updated (i.e. total view size in addition to current fragment
size) and more branches.
This patch adds a special case for single-fragment buffers to
abstract_type::deserialize. They are converted to a single_fragmented_view
before doing anything else. Templates instantiated with single_fragmented_view
should compile to better code than their multi-fragmented counterparts. If
abstract_type::deserialize is inlined, this patch should completely prevent any
performance penalties for switching from with_linearized to fragmented
deserialization.
Devirtualizes collection_type_impl::deserialize (so it can be templated) and
adds a FragmentedView overload. This will allow us to deserialize collections
with explicit cql_serialization_format directly from fragmented buffers.
The final part of the transition of deserialize from bytes_view to
FragmentedView.
Adds a FragmentedView overload to abstract_type::deserialize and
switches deserialize_visitor from bytes_view to FragmentedView, allowing
deserialization of all types with no intermediate linearization.
Although the code for it existed already, the validation function
hasn't been invoked properly. This change fixes that, adding
a validating check when converting from text to specific value
type and throwing a marshal exception if some characters
are not ASCII.
Fixes#5421Closes#7532
Currently, we linearize large UTF8 cells in order to validate them.
This can cause large latency spikes if the cell is large.
This series changes UTF8 validation to work on fragmented buffers.
This is somewhat tricky since the validation routines are optimized
for single-instruction-multiple-data (SIMD) architectures.
The unit tests are expanded to cover the new functionality.
Fixes#7448.
Closes#7449
* github.com:scylladb/scylla:
types: don't linearize utf8 for validation
test: utf8: add fragmented buffer validation tests
utils: utf8: add function to validate fragmented buffers
utils: utf8: expose validate_partial() in a header
utils: utf8: introduce validate_partial()
utils: utf8: extract a function to evaluate a single codepoint
Use the new non-linearizing validator, avoiding linearization.
Linearization can cause large contiguous memory allocations, which
in turn causes latency spikes.
Fixes#7448.
