This PR makes all of the features open source that were previously only
available in Citus Enterprise.
Features that this adds:
1. Non blocking shard moves/shard rebalancer
(`citus.logical_replication_timeout`)
2. Propagation of CREATE/DROP/ALTER ROLE statements
3. Propagation of GRANT statements
4. Propagation of CLUSTER statements
5. Propagation of ALTER DATABASE ... OWNER TO ...
6. Optimization for COPY when loading JSON to avoid double parsing of
the JSON object (`citus.skip_jsonb_validation_in_copy`)
7. Support for row level security
8. Support for `pg_dist_authinfo`, which allows storing different
authentication options for different users, e.g. you can store
passwords or certificates here.
9. Support for `pg_dist_poolinfo`, which allows using connection poolers
in between coordinator and workers
10. Tracking distributed query execution times using
citus_stat_statements (`citus.stat_statements_max`,
`citus.stat_statements_purge_interval`,
`citus.stat_statements_track`). This is disabled by default.
11. Blocking tenant_isolation
12. Support for `sslkey` and `sslcert` in `citus.node_conninfo`
We have a mechanism which ensures that newly distributed
objects are recorded during `alter extension citus update`.
However, the logic was lacking "view"s. With this commit, we make
sure that existing views are also marked as distributed during
upgrade.
Adds support for propagation ALTER VIEW commands to
- Change owner of view
- SET/RESET option
- Rename view and view's column name
- Change schema of the view
Since PG also supports targeting views with ALTER TABLE
commands, related code also added to direct such ALTER TABLE
commands to ALTER VIEW commands while sending them to workers.
CREATE FUNCTION command together with it's dependencies.
If the function depends on any nondistributable object,
function will be created only locally. Parameterless
version of create_distributed_function becomes obsolete
with this change, it will deprecated from the code with a subsequent PR.
DESCRIPTION: Implement TEXT SEARCH CONFIGURATION propagation
The change adds support to Citus for propagating TEXT SEARCH CONFIGURATION objects. TSConfig objects cannot always be created in one create statement, and instead require a create statement followed by many alter statements to get turned into the object they should represent.
To support this we add functionality to the worker to create or replace objects based on a list of statements. When the lists of the local object and the remote object correspond 1:1 we skip the creation of the object and simply mark it distributed. This is especially important for TSConfig objects as initdb pre-populates databases with a dozen configurations (for many different languages).
When the user creates a new TSConfig based on the copy of an existing configuration there is no direct link to the object copied from. Since there is no link we can't simply rely on propagating the dependencies to the worker and send a qualified
BEGIN/COMMIT transaction block or in a UDF calling another UDF.
(2) Prohibit/Limit the delegated function not to do a 2PC (or any work on a
remote connection).
(3) Have a safety net to ensure the (2) i.e. we should block the connections
from the delegated procedure or make sure that no 2PC happens on the node.
(4) Such delegated functions are restricted to use only the distributed argument
value.
Note: To limit the scope of the project we are considering only Functions(not
procedures) for the initial work.
DESCRIPTION: Introduce a new flag "force_delegation" in create_distributed_function(),
which will allow a function to be delegated in an explicit transaction block.
Fixes#3265
Once the function is delegated to the worker, on that node during the planning
distributed_planner()
TryToDelegateFunctionCall()
CheckDelegatedFunctionExecution()
EnableInForceDelegatedFuncExecution()
Save the distribution argument (Constant)
ExecutorStart()
CitusBeginScan()
IsShardKeyValueAllowed()
Ensure to not use non-distribution argument.
ExecutorRun()
AdaptiveExecutor()
StartDistributedExecution()
EnsureNoRemoteExecutionFromWorkers()
Ensure all the shards are local to the node in the remoteTaskList.
NonPushableInsertSelectExecScan()
InitializeCopyShardState()
EnsureNoRemoteExecutionFromWorkers()
Ensure all the shards are local to the node in the placementList.
This also fixes a minor issue: Properly handle expressions+parameters in distribution arguments
Before that PR we were updating citus.pg_dist_object metadata, which keeps
the metadata related to objects on Citus, only on the coordinator node. In
order to allow using those object from worker nodes (or erroring out with
proper error message) we've started to propagate that metedata to worker
nodes as well.
- citus_get_all_dependencies_for_object: emulate what Citus
would qualify as
dependency when adding
a new node
- citus_get_dependencies_for_object: emulate what Citus would qualify
as dependency when creating an
object
Example use:
```SQL
-- find all the depedencies of table test
SELECT
pg_identify_object(t.classid, t.objid, t.objsubid)
FROM
(SELECT * FROM pg_get_object_address('table', '{test}', '{}')) as addr
JOIN LATERAL
citus_get_all_dependencies_for_object(addr.classid, addr.objid, addr.objsubid) as t(classid oid, objid oid, objsubid int)
ON TRUE
ORDER BY 1;
```
Mark existing objects that are not included in distributed object infrastructure
in older versions of Citus (but now should be) as distributed, after updating
Citus successfully.
Prevent Citus extension being distributed
Because that could prevent doing rolling upgrades, where users may
prefer to upgrade the version on the coordinator but not the workers.
There could be some other edge cases, so I'd prefer to keep Citus
extension outside the picture for now.
DESCRIPTION: Disallow distributed functions for functions depending on an extension
Functions depending on an extension cannot (yet) be distributed by citus. If we would allow this it would cause issues with our dependency following mechanism as we stop following objects depending on an extension.
By not allowing functions to be distributed when they depend on an extension as well as not allowing to make distributed functions depend on an extension we won't break the ability to add new nodes. Allowing functions depending on extensions to be distributed at the moment could cause problems in that area.
Since the distributed functions are useful when the workers have
metadata, we automatically sync it.
Also, after master_add_node(). We do it lazily and let the deamon
sync it. That's mainly because the metadata syncing cannot be done
in transaction blocks, and we don't want to add lots of transactional
limitations to master_add_node() and create_distributed_function().
DESCRIPTION: Provide a GUC to turn of the new dependency propagation functionality
In the case the dependency propagation functionality introduced in 9.0 causes issues to a cluster of a user they can turn it off almost completely. The only dependency that will still be propagated and kept track of is the schema to emulate the old behaviour.
GUC to change is `citus.enable_object_propagation`. When set to `false` the functionality will be mostly turned off. Be aware that objects marked as distributed in `pg_dist_object` will still be kept in the catalog as a distributed object. Alter statements to these objects will not be propagated to workers and may cause desynchronisation.
This PR simply adds the columns to pg_dist_object and
implements the necessary metadata changes to keep track of
distribution argument of the functions/procedures.
DESCRIPTION: Distribute Types to worker nodes
When to propagate
==============
There are two logical moments that types could be distributed to the worker nodes
- When they get used ( just in time distribution )
- When they get created ( proactive distribution )
The just in time distribution follows the model used by how schema's get created right before we are going to create a table in that schema, for types this would be when the table uses a type as its column.
The proactive distribution is suitable for situations where it is benificial to have the type on the worker nodes directly. They can later on be used in queries where an intermediate result gets created with a cast to this type.
Just in time creation is always the last resort, you cannot create a distributed table before the type gets created. A good example use case is; you have an existing postgres server that needs to scale out. By adding the citus extension, add some nodes to the cluster, and distribute the table. The type got created before citus existed. There was no moment where citus could have propagated the creation of a type.
Proactive is almost always a good option. Types are not resource intensive objects, there is no performance overhead of having 100's of types. If you want to use them in a query to represent an intermediate result (which happens in our test suite) they just work.
There is however a moment when proactive type distribution is not beneficial; in transactions where the type is used in a distributed table.
Lets assume the following transaction:
```sql
BEGIN;
CREATE TYPE tt1 AS (a int, b int);
CREATE TABLE t1 AS (a int PRIMARY KEY, b tt1);
SELECT create_distributed_table('t1', 'a');
\copy t1 FROM bigdata.csv
```
Types are node scoped objects; meaning the type exists once per worker. Shards however have best performance when they are created over their own connection. For the type to be visible on all connections it needs to be created and committed before we try to create the shards. Here the just in time situation is most beneficial and follows how we create schema's on the workers. Outside of a transaction block we will just use 1 connection to propagate the creation.
How propagation works
=================
Just in time
-----------
Just in time propagation hooks into the infrastructure introduced in #2882. It adds types as a supported object in `SupportedDependencyByCitus`. This will make sure that any object being distributed by citus that depends on types will now cascade into types. When types are depending them self on other objects they will get created first.
Creation later works by getting the ddl commands to create the object by its `ObjectAddress` in `GetDependencyCreateDDLCommands` which will dispatch types to `CreateTypeDDLCommandsIdempotent`.
For the correct walking of the graph we follow array types, when later asked for the ddl commands for array types we return `NIL` (empty list) which makes that the object will not be recorded as distributed, (its an internal type, dependant on the user type).
Proactive distribution
---------------------
When the user creates a type (composite or enum) we will have a hook running in `multi_ProcessUtility` after the command has been applied locally. Running after running locally makes that we already have an `ObjectAddress` for the type. This is required to mark the type as being distributed.
Keeping the type up to date
====================
For types that are recorded in `pg_dist_object` (eg. `IsObjectDistributed` returns true for the `ObjectAddress`) we will intercept the utility commands that alter the type.
- `AlterTableStmt` with `relkind` set to `OBJECT_TYPE` encapsulate changes to the fields of a composite type.
- `DropStmt` with removeType set to `OBJECT_TYPE` encapsulate `DROP TYPE`.
- `AlterEnumStmt` encapsulates changes to enum values.
Enum types can not be changed transactionally. When the execution on a worker fails a warning will be shown to the user the propagation was incomplete due to worker communication failure. An idempotent command is shown for the user to re-execute when the worker communication is fixed.
Keeping types up to date is done via the executor. Before the statement is executed locally we create a plan on how to apply it on the workers. This plan is executed after we have applied the statement locally.
All changes to types need to be done in the same transaction for types that have already been distributed and will fail with an error if parallel queries have already been executed in the same transaction. Much like foreign keys to reference tables.
DESCRIPTION: Refactor ensure schema exists to dependency exists
Historically we only supported schema's as table dependencies to be created on the workers before a table gets distributed. This PR puts infrastructure in place to walk pg_depend to figure out which dependencies to create on the workers. Currently only schema's are supported as objects to create before creating a table.
We also keep track of dependencies that have been created in the cluster. When we add a new node to the cluster we use this catalog to know which objects need to be created on the worker.
Side effect of knowing which objects are already distributed is that we don't have debug messages anymore when creating schema's that are already created on the workers.
aykutbozkurt
Jelte Fennema
Halil Ozan Akgul
Onder Kalaci
Burak Velioglu
Nils Dijk
Teja Mupparti
Önder Kalacı
Naisila Puka
Onur Tirtir
Marco Slot
SaitTalhaNisanci
Philip Dubé