Fixes#7157
When creating/altering/describing a table, if streams are enabled, the
"latest active" stream arn should be included as LatestStreamArn.
Not doing so breaks java kinesis.
While Alternator doesn't yet support creating a table with a different
"server-side encryption" (a.k.a. encryption-at-rest) parameters, the
SSESpecification option with Enabled=false should still be allowed, as
it is just the default, and means exactly the same as would a missing
SSESpecification.
This patch also adds a test for this case, which failed on Alternator
before this patch.
Fixes#7031.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200812205853.173846-1-nyh@scylladb.com>
C++17 introduced try_emplace for maps to replace a pattern:
if(element not in a map) {
map.emplace(...)
}
try_emplace is more efficient and results in a more concise code.
This commit introduces usage of try_emplace when it's appropriate.
Tests: unit(dev)
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <4970091ed770e233884633bf6d46111369e7d2dd.1597327358.git.piotr@scylladb.com>
C++20 introduced `contains` member functions for maps and sets for
checking whether an element is present in the collection. Previously
`count` function was often used in various ways.
`contains` does not only express the intend of the code better but also
does it in more unified way.
This commit replaces all the occurences of the `count` with the
`contains`.
Tests: unit(dev)
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <b4ef3b4bc24f49abe04a2aba0ddd946009c9fcb2.1597314640.git.piotr@scylladb.com>
Currently, we cannot select more than 2^32 rows from a table because we are limited by types of
variables containing the numbers of rows. This patch changes these types and sets new limits.
The new limits take effect while selecting all rows from a table - custom limits of rows in a result
stay the same (2^32-1).
In classes which are being serialized and used in messaging, in order to be able to process queries
originating from older nodes, the top 32 bits of new integers are optional and stay at the end
of the class - if they're absent we assume they equal 0.
The backward compatibility was tested by querying an older node for a paged selection, using the
received paging_state with the same select statement on an upgraded node, and comparing the returned
rows with the result generated for the same query by the older node, additionally checking if the
paging_state returned by the upgraded node contained new fields with correct values. Also verified
if the older node simply ignores the top 32 bits of the remaining rows number when handling a query
with a paging_state originating from an upgraded node by generating and sending such a query to
an older node and checking the paging_state in the reply(using python driver).
Fixes#5101.
This field will replace max size which is currently passed once per
established rpc connection via the CLIENT_ID verb and stored as an
auxiliary value on the client_info. For now it is unused, but we update
all sites creating a read command to pass the correct value to it. In the
next patch we will phase out the old max size and use this field to pass
max size on each verb instead.
The convenience constructor of read_command now has two integer
parameter next to each other. In the next patch we intend to add another
one. This is recipe for disaster, so to avoid mistakes this patch
converts these parameters to tagged integers. This makes sure callers
pass what they meant to pass. As a matter of fact, while fixing up
call-sites, I already found several ones passing `query::max_partitions`
to the `row_limit` parameter. No harm done yet, as
`query::max_partitions` == `query::max_rows` but this shows just how
easy it is to mix up parameters with the same type.
All the places in executor.cc where we constructed an api_error with inline
strings now use api_error factory functions. Most of them, but not all of
them, were api_error::validation(). We also needed to add a couple more of
these factory functions.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
In the patch "Add exception overloads for Dynamo types", Alternator's single
api_error exception type was replaced by a more complex hierarchy of types.
The implementation was not only longer and more complex to understand -
I believe it also negated an important observation:
The "api_error" exception type is special. It is not an exception created
by code for other code. It is not meant to be caught in Alternator code.
Instead, it is supposed to contain an error message created for the *user*,
containing one of the few supported exception exception "names" described
in the DynamoDB documentation, and a user-readable text message. Throwing
such an exception in Alternator code means the thrower wants the request
to abort immediately, and this message to reach the user. These exceptions
are not designed to be caught in Alternator code. Code should use other
exceptions - or alternatives to exceptions (e.g., std::optional) for
problems that should be handled before returning a different error to the
user. Moreover, "api_error" isn't just thrown as an exception - it can
also be returned-by-value in a executor::request_return_type) - which is
another reason why it should not be subclassed.
For these reasons, I believe we should have a single api_error type, and
it's wrong to subclass it. So in this patch I am reverting the subclasses
and template added in the aforementioned patch.
Still, one correct observation made in that patch was that it is
inconvenient to type in DynamoDB exception names (no help from the editor
in completing those strings) and also error-prone. In this patch we
propse a different - simpler - solution to the same problem:
We add trivial factory functions, e.g., api_error::validation(std::string)
as a shortcut to api_error("ValidationException"). The new implementation
is easy to understand, and also more self explanatory to readers:
It is now clear that "api_error::validation()" is actually a user-visible
"api_error", something which was obscured by the name validation_exception()
used before this patch.
Finally, this patch also improves the comment in error.hh explaining the
purpose of api_error and the fact it can be returned or thrown. The fact
it should not be subclassed is legislated with a "finally". There is also
no point of this class inheriting from std::exception or having virtual
functions, or an empty constructor - so all these are dropped as well.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Subroutines needed by (in this case) streams implementation
moved from being file-static to class-static (exported).
To make putting handler routines in separate sources possible.
Because executor.cc is large and slow to compile.
Separation is nice.
Unfortunately, not all methods can be kept class-private,
since unrelated types also use them.
Reviewer suggested to instead place there is a top-level
header for export, i.e. not class-private at all.
I am skipping that for now, mainly because I can't come up
with a good file name. Can be part of a generate refactor
of helper routine organization in executor.
This patch moves the alternator latencies histograms to use the time_estimated_histogram.
The changes requires changing the defined type and use the simpler
insertion method.
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
Currently, if a user tries to CreateTable with a forbidden set of tags,
e.g., the Tags list is too long or contains an invalid value for
system:write_isolation, then the CreateTable request fails but the table
is still created. Without the tag of course.
This patch fixes this bug, and adds two test cases for it that fail
before this patch, and succeed with it. One of the test cases is
scylla_only because it checks the Scylla-specific system:write_isolation
tag, but the second test case works on DynamoDB as well.
What this patch does is to split the update_tags() function into two
parts - the first part just parses the Tags, validates them, and builds
a map. Only the second part actually writes the tags to the schema.
CreateTable now does the first part early, before creating the table,
so failure in parsing or validating the Tags will not leave a created
table behind.
Fixes#6809.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200713120611.767736-1-nyh@scylladb.com>
Manual translation from JSON to string_view is replaced
with rjson::to_string_view helper function. In one place,
a redundant string_view intermediary is removed
in favor of creating the string straight from JSON.
Message-Id: <2aa9d9fedd73f14b7640870d14db4f2f0bd7bd8a.1592936139.git.sarna@scylladb.com>
Updating tags was erroneously done locally, which means that
the schema change was not propagated to other nodes.
The new code announces new schema globally.
Fixes#6513
Branches: 4.0,4.1
Tests: unit(dev)
dtest(alternator_tests.AlternatorTest.test_update_condition_expression_and_write_isolation)
Message-Id: <3a816c4ecc33c03af4f36e51b11f195c231e7ce1.1592935039.git.sarna@scylladb.com>
Pager belongs to a different layer than CQL and thus should not be
coupled with CQL stats - if any different frontends want to use paging,
they shouldn't be forced to instantiate CQL stats at all.
Same goes with CQL restrictions, but that will require much bigger
refactoring, so is left for later.
Message-Id: <5585eb470949e3457334ffd6dba80742abf3a631.1592902295.git.sarna@scylladb.com>
The source file alternator/executor.cc has grown too much, reaching almost
4,000 lines. In this patch I move about 400 lines out of executor.cc:
1. Some functions related to serialization of sets and lists were moved to
serialization.cc,
2. Functions related to evaluating parsed expressions were moved to
expressions.cc.
The header file expressions_eval.hh was also removed - the calculate_value()
functions now live in expressions.cc, so we can just define them in
expressions.hh, no need for a separate header files.
This patch just moves code around. It doesn't make any functional changes.
Refs #5783.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
This patch provides a complete implementation for the FilterExpression
parameter - the newer syntax for filtering the results of the Query or
Scan operations.
The implementation is pretty straightforward - we already added earlier
a result-filtering framework to Alternator, and used it for the older
filtering syntax - QuryFilter and ScanFilter. All we had to do now was
to run the FilterExpression (which has the same syntax as a
ConditionExpression) on each individual items. The previous cleanup
patches were important to reduce the friction of running these expressions
on the items.
After the previous patches fixing small esoteric bugs in a few expression
functions, with this patch *all* the tests in test_filter_expression.py
now pass, and so do the two FilterExpression tests in test_query.py and
test_scan.py. As far as I know (and of course minus any bugs we'll discover
later), this marks the FilterExpression feature complete.
Fixes#5038.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
The attribute_type() function, which can be used in expressions like
ConditionExpression and FilterExpression, is supposed to generate an
error if its second parameter is not one of the known types. What we
did until now was to just report a failed check in this case.
We already had a reproducing test with FilterExpression, but in this patch
we also add a test with ConditionExpression - which fails before this
patch and passes afterwards (and of course, passes with DynamoDB).
Fixes#6641.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
The begins_with() function should report an error if a constant is
passed to it which isn't one of the supported types - string or bytes
(e.g., a number).
The code we had to check this had wrong logic, though. If the item
attribute was also a number, we silently returned false, and didn't
go on to detect that the second parameter - a constant - was a number
too and should generate an error - not be silent.
Fixed and added a reproducing test case and another test to validate
my understanding of the type of parameters that begins_with() accepts.
Fixes#6640.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
In the DynamoDB API, expressions (e.g., ConditionExpression and many more)
may contain references to column names ("#name") or to values (":val")
given in a separate part of the request - ExpressionAttributeNames and
ExpressionAttributeValues respectively.
Before this patch, we resolved these references as part of the expression's
evaluation. This approach had two downsides:
1. It often misdiagnosed (both false negatives and false positives) cases
of unused names and values in expressions. We already had two xfailing
tests with examples - which pass after this patch. This patch also
adds two additional tests, which failed before this patch and pass
with it.
2. In one of the following patches we will add support for FilterExpression,
where the same expression is used repeatedly on many items. It is a waste
(as well as makes the code uglier) to resolve the same references again
and again each time the expression is evaluated. We should be able
to do it just once.
So this patch introduces an intermediate step between parsing and evaluating
an expression - "resolving" the expression. The new resolve_*() functions
modify the already parsed expression, replacing references to attribute
names and constant values by the actual names and values taken from the
request. The resolve_*() functions also keep track which references were
used, making it very easy to check (as DynamoDB does) if there are any
unused names or values, before starting the evaluation.
The interface of evaluate() functions become much simpler - they no longer
need to know the original request (which was previously needed for
ExpressionAttributeNames/Values), the table's schema (which was previously
needed only for some error checking), keep track of which references were
used. This simplification is helpful for using the expressions in contexts
where these things (request and schema) are no longer conveniently available,
namely in FilterExpression.
A small side-benefit of this patch is that it moves a bit of code, which
handled resolving of references in expressions, from executor.cc to
expressions.cc. This is just the first step in a bigger effort to
reduce the size of executor.cc by moving code to smaller source files.
There is no attempt in this patch to move as much code as we can.
We will move more code in a separate patch in this series.
Fixes#6572.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
In the existing Alternator code, we used std::unique_ptr<rjson::value> for
passing the optional old value of an item read for a RMW operation.
The benfit of this type over the simpler "const rjson::value*" is that it
gives the callee ownership of the item, and thus the ability to move parts
of it into the response without copying them. We only used this ability in a
handful of obscure cases involving ReturnedValues, but I am not going to
break this dubious feature in this patch.
Nevertheless, a lot of internal code, like condition checks, just needs
read-only access to that previous item, so we passed a reference to the
unique_ptr, i.e., "const std::unique_ptr<rjson::value>&". This is ugly,
and also forces new code that wants to use the same condition checks (i.e.,
filtering code), to artificially allocate a unique_ptr just because that
is what these functions expect.
So in this patch, we change the utility functions such as
verify_condition_expression() and everything they use, to pass around a
"const rjson::value*" instead of a "const std::unique_ptr<rjson::value>&.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200604131352.436506-1-nyh@scylladb.com>
The DynamoDB GetItem request returns the requested item in a specific way,
wrapped in a map with a "Item" member. For historic reasons, we used the
same function that returns this (describe_item()) also in other code which
reads items - e.g. for checking conditional operations. The result is
wasteful - after adding this "Item" member we had other code to extract it,
all for no good reason. It is also ugly and confusing.
Importantly, this situation also makes it harder for me to add support for
FilterExpression. The issue is that the expression evaluator got the item
with the wrapper (from the existing ConditionExpression code) but the
filtering code had it without this wrapper, as it didn't use describe_item().
So this patch uses describe_single_item(), which doesn't add the wrapper
map, instead of describe_item(). The latter function is used just once -
to implement GetItem. The unnecessary code to unwrap the item in multiple
places was then dropped.
All the tests still pass. I also tested test_expected.py in unsafe_rmw write
isolation mode, because code only for this mode had to be modified as well.
Refs #5038.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200604092050.422092-1-nyh@scylladb.com>
Even if there are no attributes to return from PutItem requests,
we should return a valid JSON object, not an empty string.
Fixes#6568
Tests: unit(dev)
Client libraries (e.g. PynamoDB) expect the UnprocessedKeys
and UnprocessedItems attributes to appear in the response
unconditionally - it's hereby added, along with a simple test case.
Fixes#6569
Tests: unit(dev)
This patch implements the missing QueryFilter (and ScanFilter)
functionality:`
1. All operators. Previously, only the "EQ" operator was implemented.
2. Either "OR" or "AND" of conditions (previously only "AND").
3. Correctly returning Count and ScannedCount for post-filter and
pre-filter item counts, respectively.
All of the previously-xfailing tests in test_query_filter.py are now
passing.
The implementation in this patch abandons our previous attempts to
translate the DynamoDB API filters into Scylla's CQL filters.
Doing this correctly for all operators would have been exceedingly
difficult (for reasons explained in #5028), and simply not worth the
effort: CQL's filters receive a page of results and then filter them,
and we can do exactly the same without CQL's filters:
The new code just retrieves an unfiltered page of items, and then for
each of these items checks whether it passes the filters. The great thing
is that we already had code for this checking - the QueryFilter syntax is
identical to the "Expected" syntax (for conditional operations) that
we already supported, so we already had code for checking these conditions,
including all the different operators.
This patch prepares for the future need to support also the newer
FilterExpression syntax (see issue #5038), and the "filter" class
supports either type of filter - the implementation for the second
syntax is just missing and can be added (fairly easily) later.
Fixes#5028.
Refs #5038.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200603110118.399325-1-nyh@scylladb.com>
The ScanFilter and QueryFilter features are only partially implemented.
Most of their unimplemented features cause clear errors telling the user
of the unimplemented feature, but one exception is the ConditionalOperator
parameter, which can be used to "OR", instead of the default "AND", of
several conditions. Before this patch, we simply ignored this parameter -
causing wrong results to be returned instead of an error.
In this patch, ScanFilter and QueryFilter parse, instead of ignoring, the
ConditionalOperator. The common implementation, get_filtering_restrictions(),
still does not implement the OR case, but returns an error if we reach
this case instead of just ignoring it.
There is no new test. The existing test_query_filter.py::test_query_filter_or
xfailed before this patch, and continues to xfail after it, but the failure
is different (you can see it by running the test with "--runxfail"):
Before this patch, the failure was because of different results. After this
patch, the failure is because of an "unimplemented" error message.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200528214721.230587-2-nyh@scylladb.com>
We had to wait many years for it, but finally we have a starts_with()
method in C++20. Let's use it instead of ugly substr()-based code.
This is probably not a performance gain - substr() for a string_view
was already efficient. But it makes the code easier to understand,
and it allows us to rejoice in our decision to switch to C++20.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200526185812.165038-2-nyh@scylladb.com>
Alternator supports four ways in which write operations can use quorum
writes or LWT or both, which we called "write isolation policies".
Until this patch, Alternator defaulted to the most generally safe policy,
"always_use_lwt". This default could have been overriden for each table
separately, but there was no way to change this default for all tables.
This patch adds a "--alternator-write-isolation" configuration option which
allows changing the default.
Moreover, @dorlaor asked that users must *explicitly* choose this default
mode, and not get "always_use_lwt" without noticing. The previous default,
"always_use_lwt" supports any workload correctly but because it uses LWT
for all writes it may be disappointingly slow for users who run write-only
workloads (including most benchmarks) - such users might find the slow
writes so disappointing that they will drop Scylla. Conversely, a default
of "forbid_rmw" will be faster and still correct, but will fail on workloads
which need read-modify-write operations - and suprise users that need these
operations. So Dor asked that that *none* of the write modes be made the
default, and users must make an informed choice between the different write
modes, rather than being disappointed by a default choice they weren't
aware of.
So after this patch, Scylla refuses to boot if Alternator is enabled but
a "--alternator-write-isolation" option is missing.
The patch also modifies the relevant documentation, adds the same option to
our docker image, and the modifies the test-running script
test/alternator/run to run Scylla with the old default mode (always_use_lwt),
which we need because we want to test RMW operations as well.
Fixes#6452
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200524160338.108417-1-nyh@scylladb.com>
Improve error messages coming from Query's KeyCondition parameter when
wrong ComparisonOperators were used (issue discovered by @Orenef11).
At one point the error message was missing a parameter so resulted in an
internal error, while in another place the message mentioned an unuseful
number (enum) for the operator instead of its name. This patch fixes these
error messages.
Fixes#6490
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200524141800.104950-2-nyh@scylladb.com>
Our parsing of values in a KeyConditions paramter of Query was done naively.
As a result, we got bizarre error messages "condition not met: false" when
these values had incorrect type (this is issue #6490). Worse - the naive
conversion did not decode base64-encoded bytes value as needed, so
KeyConditions on bytes-typed keys did not work at all.
This patch fixes these bugs by using our existing utility function
get_key_from_typed_value(), which takes care of throwing sensible errors
when types don't match, and decoding base64 as needed.
Unfortunately, we didn't have test coverage for many of the KeyConditions
features including bytes keys, which is why this issue escaped detection.
A patch will follow with much more comprehensive tests for KeyConditions,
which also reproduce this issue and verify that it is fixed.
Refs #6490Fixes#6495
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200524141800.104950-1-nyh@scylladb.com>
When the 'forbid_rmw' write isolation policy is selected, read-modify-write
are intentionally forbidden. The error message in this case used to say:
"Read-modify-write operations not supported"
Which can lead users to believe that this operation isn't supported by this
version of Alternator - instead of realizing that this is in fact a
configurable choice.
So in this patch we just change the error message to say:
"Read-modify-write operations are disabled by 'forbid_rmw' write isolation policy. Refer to https://github.com/scylladb/scylla/blob/master/docs/alternator/alternator.md#write-isolation-policies for more information."
Fixes#6421.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200518125538.8347-1-nyh@scylladb.com>
In order to remove a FIXME, code which checks a BEGINS_WITH
relation between base64-encoded strings is computed in a way
which does not involve decoding the whole string.
In case of padding, the remainders are still decoded, but their
size is bounded by 3, which means they will be eligible for the
small string optimization.
In order to get rid of a FIXME, the code which computes the size
of decoded base64 string based only on encoded size + padding is added.
The result is an O(1) function with just a couple of ops
(15 when checking with godbolt and gcc9), so it's a general improvement
over having to allocate a string and get its size.
In order to be sure that all nodes acknowledged that a table was
created, the CreateTable request will now only return after
seeing that schema agreement was reached.
Rationale: alternator users check if the table was created by issuing
a DescribeTable request, and assume that the table was correctly
created if it returns nonempty results. However, our current
implementation of DescribeTable returns local results, which is
not enough to judge if all the other nodes acknowledge the new table.
CQL drivers are reported to always wait for schema agreement after
issuing DDL-changing requests, so there should be no harm in waiting
a little longer for alternator's CreateTable as well.
Fixes#6361
Tests: alternator(local)
Since alternator is based on Scylla, two "already exists" error types
can appear when trying to create a table - that a table itself exists,
or that its keyspace does. That's however an implementation detail,
since alternator does not have a notion of keyspaces at all.
This patch unifies the error message to simply mention that a table
already exists, and comes with a more robust test case.
If the keyspace already exists, table creation will still be attempted.
Fixes#6340
Tests: alternator(local, remote)
Change the way query result is passed from getting a reference to a
result to getting a foreign_ptr<lw_shared_ptr<query::result>>. This will
allow cas_request to keep it without copying.
The ScanIndexForward parameter is now fully implemented
and can accept ScanIndexForward=false in order to query
the partitions in reverse clustering order.
Note that reading partition slices in reverse order is less
efficient than forward scans and may put a strain on memory
usage, especially for large partitions, since the whole partition
is currently fetched in order to be reversed.
Fixes#5153
This patch allows users of storage_proxy::cas() to supply nullptr
as `query::read_command` which is supposed to skip the procedure
of reading the existing value.
The feature is used in alternator code for Read-Modify-Write
operations: some of them don't require reading previous item
values before updating.
Move `read_nothing_read_command` from alternator code to
storage_proxy layer and fabricate a new no-op command from it when
storage_proxy::cas() is used with nullptr read_command.
This allows to avoid sprinkling if-else branches all over the code
in order to check for null-equality of `cmd`.
We return from storage_proxy::query() very early with an empty
result in case we're given an empty partition_slice (which resides
inside the passed `read_command`) so this approach should be
perfectly fine.
Expand documentation for the `cas()` function to cover new
possible value for `cmd` argument.
Fixes: #6238
Tests: unit(dev, debug)
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com>
Message-Id: <20200428065235.5714-1-pa.solodovnikov@scylladb.com>
When generating tokens for parallel scan, debug mode undefined behavior
sanitizer complained that integer overflow sometimes happens when
multiplying two big values - delta and segment number.
In order to mitigate this warning, the multiplication is now split
into two smaller ones, and the generated machine code remains
identical (verified on gcc and clang via compiler explorer).
Fixes#6280
Tests: unit(dev)
