This change renames the distributed transaction manager parameter from
citus.copy_transaction_manager to citus.multi_shard_commit_protocol.
Distributed transaction manager has been used only by the COPY on hash
partitioned tables but it can be used by upcoming features so, we needed
to rename so that its name do not contain a reference to COPY.
The change also includes renames like transaction_manager_options to
commit_protocol_options and TRANSACTION_MANAGER_1PC to COMMIT_PROTOCOL_1PC.
With this change, declaration of MultiShardCommitProtocol (was
CopyTransactionManager) is moved from multi_copy.c to multi_transaction.c.
So far we've always used libpq defaults when connecting to workers; bar
special environment variables being set that'll always be the user that
started the server. That's not desirable because it prevents using
users with fewer privileges.
Thus change the various APIs creating connections to workers to always
use usernames. That means:
1) MultiClientConnect() needs to, optionally, accept a username
2) GetOrEstablishConnection(), including the underlying cache, need to
use the current user as part of the connection cache key. That way
connections for separate users are distinct, and we always use one
with the correct authorization.
3) The task tracker needs to keep track of the username associated with
a task, so it can use it when establishing connections outside the
originating session.
This commit adds a fast shard pruning path for INSERTs on
hash-partitioned tables. The rationale behind this change is
that if there exists a sorted shard interval array, a single
index lookup on the array allows us to find the corresponding
shard interval. As mentioned above, we need a sorted
(wrt shardminvalue) shard interval array. Thus, this commit
updates shardIntervalArray to sortedShardIntervalArray in the
metadata cache. Then uses the low-level API that is defined in
multi_copy to handle the fast shard pruning.
The performance impact of this change is more apparent as more
shards exist for a distributed table. Previous implementation
was relying on linear search through the shard intervals. However,
this commit relies on constant lookup time on shard interval
array. Thus, the shard pruning becomes less dependent on the
shard count.
eren
Andres Freund
Onder Kalaci
Metin Doslu
Marco Slot