When a view's PK only contains the columns that form the base's PK,
then the liveness of a particular view row is determined not only by
the base row's marker, but also by the selected and, more importantly,
unselected columns.
This patch ensures that unselected columns are considered as much as
possible, even though some limitations will still exist. In
particular, we need to represent multiple timestamps (from all the
unselected columns), but have only mechanisms to record a single
timestamp.
We also have some issues when dealing with selected column, and the
way we currently delete them. Consider the following:
create table cf (p int, c int, a int, b int, primary key (p, c))
create materialized view vcf as select a, b
from cf where p is not null and c is not null
primary key (p, c)
1) update cf using timestamp 10 set a = 1 where p = 1 and c = 1
2) delete a from cf using timestamp 11 where p = 1 and c = 1
3) update cf using timestamp 1 set a = 2 where p = 1 and c = 1
After 1), the MV should include a row with row marker @ ts10,
p = 1, c = 1, a = 1. After 2), this row should be removed.
At 3), we should add a row with row marker @ ts1, p = 1, c = 1, a = 1,
with a lower timestamp. This means that the delete should not
insert a row tombstone with timestamp @ 11, as we do now but it should
just delete the view's row marker (which exists) with ts1.
Refs #3362Fixes#3140Fixes#3361
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
When views contain a primary key column that is not part of the base
table primary key, that column determines whether the row is live or
not. We need to ensure that when that cell is dead, and thus the
derived row marker, either by normal deletion of by TTL, so is the
rest of the row.
This patch introduces the idea of shawdowing row marker. We map the
status of the regular base column in the view's PK to the view row's
marker. If this marker is dead, so is that cell in the base table, and
so should the view row become. To enforce that, a view row's dead
marker shadows the whole row if that view includes a base regular
column in its PK.
Fixes#3360
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
When a view's PK only contains the columns that form the base's PK,
then the liveness of a particular view row is determined not only by
the base row's marker, but also by the selected and, more importantly,
unselected columns. When calculating the view's row marker we need
to access those unselected columns, so we can't avoid the
read-before-write as we were doing.
Refs #3362
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
When a view's PK only contains the columns that form the base's PK,
then the liveness of a particular view row is determined not only by
the base row's marker, but also by the selected and, more importantly,
unselected columns. So, process base updates to columns unselected by
any of its views.
Refs #3362
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Not adding the partition tombstone to the current list of tombstones
may cause updates to be incorrectly generated.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Instead of lazily-initializing the regular base column in the view's
PK field, explicitly initialize it. This will be used by future
patches that don't have access to the schema when wanting to obtain
that column.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
"
Fixes to the view building process, discovered from field experience.
Tests: dtest(materialized_view_tests.py, smp=2)
"
* 'views/view-build-fixes/v1' of https://github.com/duarten/scylla:
db/view: Start view building after schema agreement
db/system_keyspace: scylla_views_builds_in_progress writes are user mem
db/view: Require configuration option to enable view building
Empty partition keys are not supported on normal tables - they cannot
be inserted or queried (surprisingly, the rules for composite
partition keys are different: all components are then allowed to be
empty). However, the (non-composite) partition key of a view could end
up being empty if that column is: a base table regular column, a
base table clustering key column, or a base table partition key column,
part of a composite key.
Fixes#3262
Refs CASSANDRA-14345
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Message-Id: <20180403122244.10626-1-duarte@scylladb.com>
If a base table or view has been dropped in one node, but another
one hasn't yet learned about it, it starts the view build process
immediately on boot, possibly calculating unneeded view updates and
causing errors at the view replica, if that replica has already
processed the schema changes. We should thus wait for schema
agreement, even if the node is a seed.
Fixes#3328
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Intended for use by unit tests, this patch allows synchronizing with
the end of a build for a particular view.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch adds the missing view building code to the eponymous class.
We consume from the reader associated with each base table until all
its views are built. If the reader reaches the end and there are
incomplete views, then a view was added while others were being built.
In such cases, we restart the reader to the beginning of the current
token, but not to the beginning of the token range, when the view is
added. Then, when we exhaust the reader, we simply create a new one
for the whole token range, and resume building the pending views.
We aim to be resource-conscious. On a given shard, at any given moment,
we consume at most from one reader. We also strive for fairness, in that
each build step inserts entries for the views of a different base. Each
build step reads and generates updates for batch_size rows. We lack a
controller, which could potentially allow us to go faster (to execute
multiple steps at the same time, or consume more rows per batch), and
also which would apply backpressure, so we could, for example, delay
executing a build step.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
The view_builder now uses the migration_manager to subscribe to schema
change events, and update its bookkeeping accordingly. We prefer this
to having the database call into the view_builder, as that would
create a cyclic dependency.
We serialize changes to the views of a particular base table, such
that schema changes do not interfere with the upcoming view building
code.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch introduces the view_builder class, a sharded service
responsible for building all defined materialized views. This process
entails walking over the existing data in a given base table, and using
it to calculate and insert the respective entries for one or more views.
This patch introduces only the bootstrap functionality, which is
responsible for loading the data stored in the system tables and
filling the in-memory data structures with the relevant information,
to be used in subsequent patches for the actual view building. The
interaction with the system tables is as follows.
Interaction with the tables in system_keyspace:
- When we start building a view, we add an entry to the
scylla_views_builds_in_progress system table. If the node restarts
at this point, we'll consider these newly inserted views as having
made no progress, and we'll treat them as new views;
- When we finish a build step, we update the progress of the views
that we built during this step by writing the next token to the
scylla_views_builds_in_progress table. If the node restarts here,
we'll start building the views at the token in the next_token
column.
- When we finish building a view, we mark it as completed in the
built views system table, and remove it from the in-progress system
table. Under failure, the following can happen:
* When we fail to mark the view as built, we'll redo the last
step upon node reboot;
* When we fail to delete the in-progress record, upon reboot
we'll remove this record.
A view is marked as completed only when all shards have finished
their share of the work, that is, if a view is not built, then all
shards will still have an entry in the in-progress system table;
- A view that a shard finished building, but not all other shards,
remains in the in-progress system table, with first_token ==
next_token.
Interaction with the distributed system table (view_build_status):
- When we start building a view, we mark the view build as being
in-progress;
- When we finish building a view, we mark the view as being built.
Upon failure, we ensure that if the view is in the in-progress
system table, then it may not have been written to this table. We
don't load the built views from this table when starting. When
starting, the following happens:
* If the view is in the system.built_views table and not the
in-progress system table, then it will be in view_build_status;
* If the view is in the system.built_views table and not in
this one, it will still be in the in-progress system table -
we detect this and mark it as built in this table too,
keeping the invariant;
* If the view is in this table but not in system.built_views,
then it will also be in the in-progress system table - we
don't detect this and will redo the missing step, for
simplicity.
View building is necessarily a sharded process. That means that on
restart, if the number of shards has changed, we need to calculate
the most conservative token range that has been built, and build
the remainder.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
While we now send view mutations asynchronously in the normal view
write path, other processes interested in sending view updates, such
as streaming or view building, may wish to do it synchronously.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Provide a virtual reader so users can query the in-progress view table
in a way compatible with Apache Cassandra.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
When the cluster is changed (nodes added or removed), ranges of tokens
are moved between nodes. Scylla initiates a streaming process between an
old and a new owner of the range, which can take a long time. During
that streaming time, the new owner of the range is known as a "pending node"
for this range, and all updates must go to both the old owner (in case the
movement fails!) and the pending node (in case the movement succeeds).
For materialized views, because they are ordinary tables, streaming moves
all the view's data that existed before the streaming started. But we did
not send updates done to the view *during* the streaming. A dtest
demonstrates that the new node will miss some of the view update, and will
require a repair of the view tables immediately after the cluster change
ends, which is not good. To fix that, we need to send every new update
that happens during the streaming also to the "pending node". We already
did this properly for base-table updates, but not to the view updates:
Each base table replica wrote to only one paired view table replica,
and nobody wrote to the new pending node (in case where there is one,
for the particular view token involved).
In this patch, we make sure that all view updates go also to the "pending
nodes" when there are any. We do the same thing that Cassandra does, which
is - *all* base replicas write the update to the pending node(s).
Arguably, it is inefficient that all replicas send the update to the same
node. In most cases it is enough to send it from just one base replica -
the one who is slated to be the new node's pair. I opened
https://issues.apache.org/jira/browse/CASSANDRA-14262 about this idea.
But that is an optimization. The patch as-is already fixes the bug.
Fixes#3211
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20180313171853.17283-1-nyh@scylladb.com>
This patch adds a "row_locker" class providing locking (shard-locally) of
individual clustering rows or entire partitions, and both exclusive and
shared locks (a.k.a. reader/writer lock).
As we'll see in a following patch, we need this locking capability for
materialized views, to serialize the read-modify-update modifications
which involve the same rows or partitions.
The new row_locker is significantly different from the existing cell_locker.
The two main differences are that 1. row_locker also supports locking the
entire partition, not just individual rows (or cells in them), and that
2. row_locker supports also shared (reader) locks, not just exclusive locks.
For this reason we opted for a new implementation, instead of making large
modificiations to the existing cell_locker. And we put the source files
in the view/ directory, because row_locker's requirements are pretty
specific to the needs of materialized views.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Using Materialized Views, if the base table has static columns,
and the update in base table mutates static and non static rows,
the streamed_mutation is stopped before process non static row.
The patch avoids stopping the stream_mutation and adds a test case.
Message-Id: <20171220173434.25091-1-tavares.george@gmail.com>
- 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 patch implements clustering_prefix_matches() in terms of
abstract_restriction::is_satisfied_by() instead of ranges, which
supports filtering just a subset of the clustering columns.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch implements partition_key_matches() in terms of
abstract_restriction::is_satisfied_by() instead of ranges, which
supports filtering just a component of a compound partition key.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch ensures we take into account the liveness of the base's
regular column in the view's pk when generating view updates.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
When generating updates for a materialized view we need to read the
existing base row, to be able to determine the primary key of the view
row the new base update will supplant, in case the view includes a
base non-primary key column in its own primary key. That old view row
will be tombstoned or updated, if it exists, depending on the difference
between the new base row and the existing one, if any.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Introduce the calculate_affected_clustering_ranges() function to
calculate the smallest subject of affected clustering ranges that we
need to query for.
The update_requires_read_before_write() function checks whether
a view is potentially affected by the base update.
The patch also cleans up the may_be_affected_by() function.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
If a base table regular columns is part of the view's pk, and if that
column changes, we should replace the entry, by deleting the row(s)
with the old value and inserting a new one.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch stores the base_non_pk_column_in_view column as column_id,
which is more convenient, and it also stores a two-level optional to
encode both lazy initialization and the absence of such a column.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
More pointedly: Expose columns as is (currently
all_columns_in_select_order), expose name->column mapping more
appropriately named.
Renaming like this is not strictly neccesary, but there is a point to
trying to keep nomenclature similar-ish with origin, esp. when select
order column need to become filtered (spoiler alert).
This patch replaces the current row tombstone representation by a
row_tombstone.
The intent of the patch is thus to reify the idea of shadowable
tombstones, that up until now we considered all materialized view row
tombstones to be.
We need to distinguish shadowable from non-shadowable row tombstones
to support scenarios such as, when inserting to a table with a
materialzied view:
1. insert into base (p, v1, v2) values (3, 1, 3) using timestamp 1
2. delete from base using timestamp 2 where p = 3
3. insert into base (p, v1) values (3, 1) using timestamp 3
These should yield a view row where v2 is definitely null, but with
the current implementation, v2 will pop back with its value v2=3@TS=1,
even though its dead in the base row. This is because the row
tombstone inserted at 2) is a shadowable one.
This patch only addresses the memory representation of such
row_tombstones.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
The write path uses a base schema at a particular version, and we
want it to use the materialized views at the corresponding version.
To achieve this, we need to map the state currently in db::view::view
to a particular schema version, which this patch does by introducing
the view_info class to hold the state previously in db::view::view,
and by having a view schema directly point to it.
The changes in the patch are thus:
1) Introduce view_info to hold the extra view state;
2) Point to the view_info from the schema;
3) Make the functions in the now stateless db::view::view non-member;
4) Remove the db::view::view class.
All changes are structural and don't affect current behavior.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
mutation_fragments are going to be caching their size in memory. In
order to be able to invalidate that correctly, they need to know when
that size may change (but avoid invalidation when it is not necessary).
This adds a function mutate_MV() which takes view mutations and sends
them to the appropriate nodes (this may be the current node, or a
remote node).
This is only a partial implementation - we still don't do the local
batch log (to survive reboots and failures) and some other stuff which
is left commented out.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
A function to find the appropriate replica to send a view update to.
This patch creates a new source file db/view/view.cc. We should
eventually move a lot more of the materialized views code there.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
This patch adds the view_update_builder class, which is responsible
for calculating the mutations to apply to a column family's
materialized views, given a streamed_mutation representing an update
to the base table and a streamed_mutation representing the
pre-existing rows which the update covers.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch adds the view_updates::generate_update() function to
generate view updates given a base row update and the corresponding,
pre-existing row. This function will decide which of the previously
introduced functions to call based on whether there is a pre-existing
row and whether there exists a regular base column that's part of the
view's PK.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch adds a function to replace a view row given a base
table update and the pre-existing row, which simply deletes the old
view entry and adds a new one.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch introduces the view_updates::update_entry function,
which creates the updates to apply to the existing view entry given
the base table row before and after the update.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch introduces the view_updates::delete_old_entry function,
which creates a view row mutation to delete an entry given an updated
base table row.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
This patch introduces the view_updates::create_entry function, which
creates a view row mutation given a new base table row.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
