* Removed distributed dependency in columnar_metadata.c
* Changed columnar_debug.c so that it no longer needed distributed/tuplestore and made it return a record instead of a tuplestore
* removed distributed/commands.h dependency
* Made columnar_tableam.c dependency-free
* Fixed spacing for columnar_store_memory_stats function
* indentation fix
* fixed test failures
* Require superuser while activating a node
With this change, we require ActiveNode() (hence citus_add_node(),
citus_activate_node()) explicitly require for a superuser.
Before this commit, these functions were designed to work with
non-superuser roles with the relevent GRANTs given.
However, that is not a widely used way for calling the functions
above.
Due to possibility of non-super user calling the UDFs, they were
designed in a way that some commands were using some additional
short-lived superuser connections. That is:
(a) breaking transactional behavior (e.g., ROLLBACK
wouldn't fully rollback the whole transaction)
(b) Making it very complicated to reason about which
parts of the node activation goes over which connections,
and becoming vulnerable to deadlocks / visibility issues.
In addition to starting a new transaction, we also need to tell other
backends --including the ones spawned for connections opened to
localhost to build indexes on shards of this relation-- that concurrent
index builds can safely ignore us.
Normally, DefineIndex() only does that if index doesn't have any
predicates (i.e.: where clause) and no index expressions at all.
However, now that we already called standard process utility, index
build on the shell table is finished anyway.
The reason behind doing so is that we cannot guarantee not grabbing any
snapshots via adaptive executor, and the backends creating indexes on
local shards (if any) might block on waiting for current xact of the
current backend to finish, which would cause self deadlocks that are not
detectable.
With https://github.com/citusdata/citus/pull/5493 we introduced
metadata specific connections.
With this connection we guarantee that there is a single metadata connection.
But note that this connection can be used for any other operation.
In other words, this connection is not only reserved for metadata
operations.
However, as https://github.com/citusdata/citus-enterprise/issues/715 showed
us that the logic has a flaw. We allowed ineligible connections to be
picked as metadata connections: such as exclusively claimed connections
or not fully initialized connections.
With this commit, we make sure that we only consider eligable connections
for metadata operations.