`duration` is a new native type that was introduced in Cassandra 3.10 [1].
Support for parsing and the internal representation of the type was added in
8fa47b74e8.
Important note: The version of cqlsh distributed with Scylla does not have
support for durations included (it was added to Cassandra in [2]). To test this
change, you can use cqlsh distributed with Cassandra.
Duration types are useful when working with time-series tables, because they can
be used to manipulate date-time values in relative terms.
Two interesting applications are:
- Aggregation by time intervals [3]:
`SELECT * FROM my_table GROUP BY floor(time, 3h)`
- Querying on changes in date-times:
`SELECT ... WHERE last_heartbeat_time < now() - 3h`
(Note: neither of these is currently supported, though columns with duration
values are.)
Internally, durations are represented as three signed counters: one for months,
for days, and for nanoseconds. Each of these counters is serialized using a
variable-length encoding which is described in version 5 of the CQL native
protocol specification.
The representation of a duration as three counters means that a semantic
ordering on durations doesn't exist: Is `1mo` greater than `1mo1d`? We cannot
know, because some months have more days than others. Durations can only have a
concrete absolute value when they are "attached" to absolute date-time
references. For example, `2015-04-31 at 12:00:00 + 1mo`.
That duration values are not comparable presents some difficulties for the
implementation, because most CQL types are. Like in Cassandra's implementation
[2], I adopted a similar strategy to the way restrictions on the `counter` type
are checked. A type "references" a duration if it is either a duration or it
contains a duration (like a `tuple<..., duration, ...>`, or a UDT with a
duration member).
The following restrictions apply on durations. Note that some of these contexts
are either experimental features (materialized views), or not currently
supported at run-time (though support exists in the parser and code, so it is
prudent to add the restrictions now):
- Durations cannot appear in any part of a primary key, either for tables or
materialized views.
- Durations cannot be directly used as the element type of a `set`, nor can they
be used as the key type of a `map`. Because internal ordering on durations is
based on a byte-level comparison, this property of Cassandra was intended to
help avoid user confusion around ordering of collection elements.
- Secondary indexes on durations are not supported.
- "Slice" relations (<=, <, >=, >) are not supported on durations with `WHERE`
restrictions (like `SELECT ... WHERE span <= 3d`). Multi-column restrictions
only work with clustering columns, which cannot be `duration` due to the
first rule.
- "Slice" relations are not supported on durations with query conditions (like
`UPDATE my_table ... IF span > 5us`).
Backwards incompatibility note:
As described in the documentation [4], duration literals take one of two
forms: either ISO 8601 formats (there are three), or a "standard" format. The ISO
8601 formats start with "P" (like "P5W"). Therefore, identifiers that have this
form are no longer supported.
Fixes#2240.
[1] https://issues.apache.org/jira/browse/CASSANDRA-11873
[2] bfd57d13b7
[3] https://issues.apache.org/jira/browse/CASSANDRA-11871
[4] http://cassandra.apache.org/doc/latest/cql/types.html#working-with-durations
- introcduced "seastarx.hh" header, which does a "using namespace seastar";
- 'net' namespace conflicts with seastar::net, renamed to 'netw'.
- 'transport' namespace conflicts with seastar::transport, renamed to
cql_transport.
- "logger" global variables now conflict with logger global type, renamed
to xlogger.
- other minor changes
This changes announce_migration() to return a change event directory in
schema_altering_statement base class. It's needed for drop index
statement, which does not know the keyspace or column family until it
looks up them based on the index. Two stage approach of announcing a
migration and then creating the change event won't work because in the
latter stage, the lookup will fail. The same change in
announce_migration() has been applied to Apache Cassandra.
"The version of create_index_statement class that was translated to C++
is pretty old by now. This series of cleanups brings it closer to Apache
Cassandra trunk to make it easier to bring over more secondary index
code to Scylla."
* 'penberg/create-index-stmt-cleanup/v1' of github.com:cloudius-systems/seastar-dev:
cql3/statements/create_index_statement: Move target validation
cql3/statements/create_index_statement: Remove static column validation
cql3/statements/create_index_statement: Extract validations
cql3/statements/create_index_statement: Kill bogus custom validation
cql3/statements/create_index_statement: Add materialized view to validate()
cql3/statements/create_index_statement: Remove validation
Extract specific validations to separate functions to preserve the same
structure as Apache Cassandra code and make it easier to add support for
multiple index targets.
Rejecting custom indices is bogus because it's just a configuration
mechanism like replication strategy, for example. Furthermore, it's
needed for SASI indices, which we likely need to be compatible with.
The validation was removed in Apacha Cassandra commit 0626be8 ("New 2i
API and implementations for built in indexes"). Let's also remove it
from our code so that we remove one dependency to the obsolete db/index/
code.
Use seastar::checked_ptr<weak_ptr<pepared_statement>> instead of shared_ptr for passing prepared statements around.
This allows an easy tracking and handling of statements invalidation.
This implementation will throw an exception every time an invalidated
statement reference is dereferenced.
Signed-off-by: Vlad Zolotarov <vladz@scylladb.com>
This patch changes the migration path for table updates such that the
base table mutations are sent and applied atomically with the view
schema mutations.
This ensures that after schema merging, we have a consistent mapping
of base table versions to view table versions, which will be used in
later patches.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
To prepare for the separation of prepared and raw schema_altering_statements,
avoid the reliance this class implementing both the raw and prepared
variants and the use of shared_from_this().
Use get_storage_proxy() and get_local_storage_proxy() helpers under the
hood to simplify migration manager API users.
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
In preparation for adding listener state to migration manager, use
sharded<> for migration manager.
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Fix index name case sensitivity as per Origin commit 68be72f ("Fix
case-sensitivity of index name on CREATE/DROP INDEX") which addressed
CASSANDRA-8365.
The grammar rules were imported from the following Origin commit:
ebc50d783505854f04f183297ad3009b9095b07e
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Persist column family's "is_dense" value to system tables. Please note
that we throw an exception if "is_dense" is null upon read. That needs
to be fixed later by inferring the value from other information like
Origin does.
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
