Currently we hold group0_guard only during DDL statement's execute()
function, but unfortunately some statements access underlying schema
state also during check_access() and validate() calls which are called
by the query_processor before it calls execute. We need to cover those
calls with group0_guard as well and also move retry loop up. This patch
does it by introducing new function to cql_statement class take_guard().
Schema altering statements return group0 guard while others do not
return any guard. Query processor takes this guard at the beginning of a
statement execution and retries if service::group0_concurrent_modification
is thrown. The guard is passed to the execute in query_state structure.
Fixes: #13942
Message-ID: <ZNsynXayKim2XAFr@scylladb.com>
This reverts commit 70b5360a73. It generates
a failure in group0_test .test_concurrent_group0_modifications in debug
mode with about 4% probability.
Fixes#15050
Currently we hold group0_guard only during DDL statement's execute()
function, but unfortunately some statements access underlying schema
state also during check_access() and validate() calls which are called
by the query_processor before it calls execute. We need to cover those
calls with group0_guard as well and also move retry loop up. This patch
does it by introducing new function to cql_statement class take_guard().
Schema altering statements return group0 guard while others do not
return any guard. Query processor takes this guard at the beginning of a
statement execution and retries if service::group0_concurrent_modification
is thrown. The guard is passed to the execute in query_state structure.
Fixes: #13942
Message-ID: <ZNSWF/cHuvcd+g1t@scylladb.com>
Not wired in yet. SELECT * FROM MUTATION_FRAGMENTS($table) is a new
select statement sub-type, which allows dumping the underling mutations
making up the data of a given table. The output of this statement is
mutation-fragments presented as CQL rows. Each row corresponds to a
mutation-fragment. Subsequently, the output of this statement has a
schema that is different than that of the underlying table.
Data is always read from the local replica, on which the query is
executed. Migrating queries between coordinators is not allowed.
select_statement::do_execute() has a fast path where it forwards
to execute_without_checking_exception_message_non_aggregate_unpaged().
In this fast path, we aren't paging (a good reason for that is reading
a partition without clustering keys) and in the slow/slower paths
we page and/or perform complex processing like aggregation.
The fast path doesn't need any continuations, but the slow/slower paths
do. Split them off so that the slow/slower paths can be coroutinized
without impacting the fast path.
There are two execute() overloads, but they don't do the same thing - one is a
partial implementation of the other.
The same is true of two execute_without_checking_exception_message() overloads.
Change the name of the subordinate overload to indicate its role. Overloads should
be used when the only difference between overloads is the argument type, not when
one does a subset of the other.
The CQL binary protocol introduced "unset" values in version 4
of the protocol. Unset values can be bound to variables, which
cause certain CQL fragments to be skipped. For example, the
fragment `SET a = :var` will not change the value of `a` if `:var`
is bound to an unset value.
Unsets, however, are very limited in where they can appear. They
can only appear at the top-level of an expression, and any computation
done with them is invalid. For example, `SET list_column = [3, :var]`
is invalid if `:var` is bound to unset.
This causes the code to be littered with checks for unset, and there
are plenty of tests dedicated to catching unsets. However, a simpler
way is possible - prevent the infiltration of unsets at the point of
entry (when evaluating a bind variable expression), and introduce
guards to check for the few cases where unsets are allowed.
This is what this long patch does. It performs the following:
(general)
1. unset is removed from the possible values of cql3::raw_value and
cql3::raw_value_view.
(external->cql3)
2. query_options is fortified with a vector of booleans,
unset_bind_variable_vector, where each boolean corresponds to a bind
variable index and is true when it is unset.
3. To avoid churn, two compatiblity structs are introduced:
cql3::raw_value{,_view}_vector_with_unset, which can be constructed
from a std::vector<raw_value{,_view/}>, which is what most callers
have. They can also be constructed with explicit unset vectors, for
the few cases they are needed.
(cql3->variables)
4. query_options::get_value_at() now throws if the requested bind variable
is unset. This replaces all the throwing checks in expression evaluation
and statement execution, which are removed.
5. A new query_options::is_unset() is added for the users that can tolerate
unset; though it is not used directly.
6. A new cql3::unset_operation_guard class guards against unsets. It accepts
an expression, and can be queried whether an unset is present. Two
conditions are checked: the expression must be a singleton bind
variable, and at runtime it must be bound to an unset value.
7. The modification_statement operations are split into two, via two
new subclasses of cql3::operation. cql3::operation_no_unset_support
ignores unsets completely. cql3::operation_skip_if_unset checks if
an operand is unset (luckily all operations have at most one operand that
tolerates unset) and applies unset_operation_guard to it.
8. The various sites that accept expressions or operations are modified
to check for should_skip_operation(). This are the loops around
operations in update_statement and delete_statement, and the checks
for unset in attributes (LIMIT and PER PARTITION LIMIT)
(tests)
9. Many unset tests are removed. It's now impossible to enter an
unset value into the expression evaluation machinery (there's
just no unset value), so it's impossible to test for it.
10. Other unset tests now have to be invoked via bind variables,
since there's no way to create an unset cql3::expr::constant.
11. Many tests have their exception message match strings relaxed.
Since unsets are now checked very early, we don't know the context
where they happen. It would be possible to reintroduce it (by adding
a format string parameter to cql3::unset_operation_guard), but it
seems not to be worth the effort. Usage of unsets is rare, and it is
explicit (at least with the Python driver, an unset cannot be
introduced by ommission).
I tried as an alternative to wrap cql3::raw_value{,_view} (that doesn't
recognize unsets) with cql3::maybe_unset_value (that does), but that
caused huge amounts of churn, so I abandoned that in favor of the
current approach.
Closes#12517
Restrictions that might be used by an index
are currently being kept as shared_ptr<restrictions>.
This stand in the way of replacing _parition_key_restrictions
with an expression as an expression can't be cast to
shared_ptr<restriction>.
Change shared_ptr<restriction> to expression everywhere
where necessary in index operations.
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
After fcb8d040 ("treewide: use Software Package Data Exchange
(SPDX) license identifiers"), many dual-licensed files were
left with empty comments on top. Remove them to avoid visual
noise.
Closes#10562
It seams that batch prepared statements always return false for
depends_on_keyspace and depends_on_column_family, this in turn
renders the removal criteria from the cache to always be false
which result by the queries not being evicted.
Here we change the functions to return the true state meaning,
they will return true if any of the sub queries is dependant upon
the keyspace or column family.
In this fix we first make the API more coherent and then use this new API to implement
the batch statement's dependency test.
Fixes#10129
Signed-off-by: Eliran Sinvani <eliransin@scylladb.com>
Closes#10132
* github.com:scylladb/scylla:
prepared_statements: Invalidate batch statement too
cql3 statements: Change dependency test API to express better it's purpose
Recently, coordinator_result was introduced as an alternative for
exceptions. It was placed in the main "exceptions/exceptions.hh" header,
which virtually every single source file in Scylla includes.
But unfortunately, it brings in some heavy header files and templates,
leading to a lot of wasted build time - ClangBuildAnalyzer measured that
we include exceptions.hh in 323 source files, taking almost two seconds
each on average.
In this patch, we split the coordinator_result feature into a separate
header file, "exceptions/coordinator_result", and only the few places
which need it include the header file. Unfortunately, some of these
few places are themselves header, so the new header file ends up being
included in 100 source files - but 100 is still much less than 323 and
perhaps we can reduce this number 100 later.
After this patch, the total Scylla object-file size is reduced by 6.5%
(the object size is a proxy for build time, which I didn't directly
measure). ClangBuildAnalyzer reports that now each of the 323 includes
of exceptions.hh only takes 80ms, coordinator_result.hh is only included
100 times, and virtually all the cost to include it comes from Boost's
result.hh (400ms per inclusion).
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20220228204323.1427012-1-nyh@scylladb.com>
purpose
Cql statements used to have two API functions, depends_on_keyspace and
depends_on_column_family. The former, took as a parameter only a table
name, which makes no sense. There could be multiple tables with the same
name each in a different keyspace and it doesn't make sense to
generalize the test - i.e to ask "Does a statement depend on any table
named XXX?"
In this change we unify the two calls to one - depends on that takes a
keyspace name and optionally also a table name, that way every logical
dependency tests that makes sense is supported by a single API call.
Adjusts the indexed_table_select_statement so that it uses the
result-aware methods in storage_proxy and propagates failed results as
result_message::exception.
The select_statement will be able to propagate coordinator failures
without throwing, so it's important to override the default
implementations of execute and excecute_without... so that the first
calls the latter and not the other way around.
Adds:
- Includes for result-related helper methods (to be used in later
commits),
- Alias for coordinator_result,
- The wrap_result_to_error_message function - a bit similar to
utils::result_wrap. Adapts a callable T -> shared_ptr<result_message>
to take result<T> -> shared_ptr<result_message>. If the result is
failed, it converts it into result_message::exception and returns.
Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
This is the largest user of proxy argument. Fix them all and
their callers (all sit in the same .cc file).
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
The batch_ , modification_ and select_ statements get proxy from
query processor just to push it through execution stage. Simplify
that by pushing the query processor itself.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
This is mostly a sed script that replaces methods' first argument
plus fixes of compiler-generated errors.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Stop using database (and including database.hh) for schema related
purposes and use data_dictionary instead.
data_dictionary::database::real_database() is called from several
places, for these reasons:
- calling yet-to-be-converted code
- callers with a legitimate need to access data (e.g. system_keyspace)
but with the ::database accessor removed from query_processor.
We'll need to find another way to supply system_keyspace with
data access.
- to gain access to the wasm engine for testing whether used
defined functions compile. We'll have to find another way to
do this as well.
The change is a straightforward replacement. One case in
modification_statement had to change a capture, but everything else
was just a search-and-replace.
Some files that lost "database.hh" gained "mutation.hh", which they
previously had access to through "database.hh".
The generate_view_paging_state_from_base_query_results() has unused
proxy argument that's carried over quite a long stack for nothing.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Message-Id: <20211210175203.26197-1-xemul@scylladb.com>
Instead of calculating _restrictions->need_filtering()
we can calculate it only once and then use this computed variable.
It turns out that _restrictions->need_filtering() is called
during execution of prepared statements and it has to scan through the whole AST,
so doing it only once gives us a performance gain.
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
This warning can catch a virtual function that thinks it
overrides another, but doesn't, because the two functions
have different signatures. This isn't very likely since most
of our virtual functions override pure virtuals, but it's
still worth having.
Enable the warning and fix numerous violations.
Closes#9347
Original code which introduced enforcing page limits for indexed
statements created a new constant for max result size in bytes.
Botond reported that we already have such a constant, so it's now
used instead of reinventing it from scratch.
Closes#8839
Indexed select statements fetch primary key information from
their internal materialized views and then use it to query
the base table. Unfortunately, the current mechanism for retrieving
base table rows makes it easy to overwhelm the replicas with unbounded
concurrency - the number of concurrent ops is increased exponentially
until a short read is encountered, but it's not enough to cap the
concurrency - if data is fetched row-by-row, then short reads usually
don't occur and as a result it's easy to see concurrency of 1M or
higher. In order to avoid overloading the replicas, the concurrency
of indexed queries is now capped at 4096 and additionally throttled
if enough results are already fetched. For paged queries it means that
the query returns as soon as 1MB of data is ready, and for unpaged ones
the concurrency will no longer be doubled as soon as the previous
iteration fetched 1MB of results.
The fixed 4096 value can be subject to debate, its reasoning is as follows:
for 2KiB rows, so moderately large but not huge, they result in
fetching 10MB of data, which is the granularity used by replicas.
For 200B rows, which is rather small, the result would still be
around 1MB.
At the same time, 4096 separate tasks also means 4096 allocations,
so increasing the number also strains the allocator.
Fixes#8799
Tests: unit(release),
manual: observing metrics of modified index_paging_test
Closes#8814
* github.com:scylladb/scylla:
cql3: limit the transitional result size for indexed queries
cql3: return indexed pages after 1MB worth of data
cql3: limit the concurrency of indexed statements
Currently there's no practical limit of the resulting page size
for an indexed query, because it simply translates a page worth
of base primary keys into base rows. In order to avoid sending
too large pages, the result is returned after hitting a 1MB limit.
Indexed select statements fetch primary key information from
their internal materialized views and then use it to query
the base table. Unfortunately, the current mechanism for retrieving
base table rows makes it easy to overwhelm the replicas with unbounded
concurrency - the number of concurrent ops is increased exponentially
until a short read is encountered, but it's not enough to cap the
concurrency - if data is fetched row-by-row, then short reads usually
don't occur and as a result it's easy to see concurrency of 1M or
higher. In order to avoid overloading the replicas, the concurrency
of indexed queries is now capped at 4096.
The number can be subject to debate, its reasoning is as follows:
for 2KiB rows, so moderately large but not huge, they result in
fetching 10MB of data, which is the granularity used by replicas.
For 200B rows, which is rather small, the result would still be
around 1MB.
At the same time, 4096 separate tasks also means 4096 allocations,
so increasing the number also strains the allocator.
Fixes#8799
Tests: unit(release),
manual: observing metrics of modified index_paging_test
Currently the statement's execute() method accepts storage
proxy as the first argument. This is enough for all of them
but schema altering ones, because the latter need to call
migration manager's announce.
To provide the migration manager to those who need it it's
needed to have some higher-level service that the proxy. The
query processor seems to be good candidate for it.
Said that -- all the .execute()s now accept the querty
processor instead of the proxy and get the proxy itself from
the query processor.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
First of all, select statement is extended with an 'attrs' field,
which keeps the per-query attributes. Currently, only TIMEOUT
parameter is legal to use, since TIMESTAMP and TTL bear no meaning
for reads.
Secondly, if TIMEOUT attribute is set, it will be used as the effective
timeout for a particular query.
Switches token column computation to (new) token_column_computation,
which fixes#7443, because new token column will be compared using
signed comparisons, not the previous unsigned comparison of CQL bytes
type.
This column computation type is only set if cluster supports
correct_idx_token_in_secondary_index feature to make sure that all nodes
will be able to compute (new) token_column_computation. Also old
indexes will need to be rebuilt to take advantage of this fix, as new
token column computation type is only set for new indexes.
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.
* Pass raw::select_statement::parameters as lw_shared_ptr
* Some more const cleanups here and there
* lists,maps,sets::equals now accept const-ref to *_type_impl
instead of shared_ptr
* Remove unused `get_column_for_condition` from modification_statement.hh
* More methods now accept const-refs instead of shared_ptr
Every call site where a shared_ptr was required as an argument
has been inspected to be sure that no dangling references are
possible.
Tests: unit(dev, debug)
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com>
Message-Id: <20200220153204.279940-1-pa.solodovnikov@scylladb.com>
Change the way `service::pager::paging_state` is passed around
from `shared_ptr` to `lw_shared_ptr`. It's safe since
`paging_state` is final.
Tests: unit(dev, debug)
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com>
