mirror of https://github.com/citusdata/citus.git
Fixes review comments
gindibay
parent
d9cecba67c
commit
48a5450d59
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@ -9,7 +9,6 @@
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#include "funcapi.h"
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#include "utils/plancache.h"
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#include "access/genam.h"
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#include "access/heapam.h"
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#include "access/htup.h"
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@ -102,8 +101,8 @@ static HeapTuple GetNodeByNodeId(int32 nodeId);
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static int32 GetNextGroupId(void);
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static int GetNextNodeId(void);
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static void InsertPlaceholderCoordinatorRecord(void);
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static void InsertNodeRow(int nodeid, char *nodename, int32 nodeport, NodeMetadata
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*nodeMetadata);
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static void InsertNodeRow(int nodeid, char *nodename, int32 nodeport,
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NodeMetadata *nodeMetadata);
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static void DeleteNodeRow(char *nodename, int32 nodeport);
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static void BlockDistributedQueriesOnMetadataNodes(void);
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static WorkerNode * TupleToWorkerNode(TupleDesc tupleDescriptor, HeapTuple heapTuple);
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@ -163,7 +162,6 @@ PG_FUNCTION_INFO_V1(citus_coordinator_nodeid);
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PG_FUNCTION_INFO_V1(citus_is_coordinator);
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PG_FUNCTION_INFO_V1(citus_internal_mark_node_not_synced);
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/*
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* DefaultNodeMetadata creates a NodeMetadata struct with the fields set to
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* sane defaults, e.g. nodeRack = WORKER_DEFAULT_RACK.
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@ -547,7 +545,8 @@ citus_disable_node(PG_FUNCTION_ARGS)
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"metadata is not allowed"),
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errhint("You can force disabling node, SELECT "
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"citus_disable_node('%s', %d, "
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"synchronous:=true);", workerNode->workerName,
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"synchronous:=true);",
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workerNode->workerName,
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nodePort),
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errdetail("Citus uses the first worker node in the "
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"metadata for certain internal operations when "
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@ -696,8 +695,7 @@ citus_set_node_property(PG_FUNCTION_ARGS)
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else
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{
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ereport(ERROR, (errmsg(
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"only the 'shouldhaveshards' property can be set using this function"
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)));
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"only the 'shouldhaveshards' property can be set using this function")));
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}
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TransactionModifiedNodeMetadata = true;
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@ -1178,6 +1176,81 @@ LockShardsInWorkerPlacementList(WorkerNode *workerNode, LOCKMODE lockMode)
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}
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BackgroundWorkerHandle *
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CheckBackgroundWorkerToObtainLocks(int32 lock_cooldown)
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{
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BackgroundWorkerHandle *handle = NULL;
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handle = StartLockAcquireHelperBackgroundWorker(MyProcPid, lock_cooldown);
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if (!handle)
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{
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/*
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* We failed to start a background worker, which probably means that we exceeded
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* max_worker_processes, and this is unlikely to be resolved by retrying. We do not want
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* to repeatedly throw an error because if citus_update_node is called to complete a
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* failover then finishing is the only way to bring the cluster back up. Therefore we
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* give up on killing other backends and simply wait for the lock. We do set
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* lock_timeout to lock_cooldown, because we don't want to wait forever to get a lock.
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*/
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SetLockTimeoutLocally(lock_cooldown);
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ereport(WARNING, (errmsg(
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"could not start background worker to kill backends with conflicting"
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" locks to force the update. Degrading to acquiring locks "
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"with a lock time out."),
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errhint(
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"Increasing max_worker_processes might help.")));
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}
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return handle;
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}
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/*
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* This function is used to lock shards in a primary node.
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* If force is true, we start a background worker to kill backends holding
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* conflicting locks with this backend.
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*
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* If the node is a primary node we block reads and writes.
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*
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* This lock has two purposes:
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*
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* - Ensure buggy code in Citus doesn't cause failures when the
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* nodename/nodeport of a node changes mid-query
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*
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* - Provide fencing during failover, after this function returns all
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* connections will use the new node location.
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*
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* Drawback:
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*
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* - This function blocks until all previous queries have finished. This
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* means that long-running queries will prevent failover.
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*
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* In case of node failure said long-running queries will fail in the end
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* anyway as they will be unable to commit successfully on the failed
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* machine. To cause quick failure of these queries use force => true
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* during the invocation of citus_update_node to terminate conflicting
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* backends proactively.
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*
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* It might be worth blocking reads to a secondary for the same reasons,
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* though we currently only query secondaries on follower clusters
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* where these locks will have no effect.
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*/
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BackgroundWorkerHandle *
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LockPlacementsWithBackgroundWorkersInPrimaryNode(WorkerNode *workerNode, bool force, int32
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lock_cooldown)
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{
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BackgroundWorkerHandle *handle = NULL;
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if (NodeIsPrimary(workerNode))
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{
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if (force)
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{
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handle = CheckBackgroundWorkerToObtainLocks(lock_cooldown);
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}
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LockShardsInWorkerPlacementList(workerNode, AccessExclusiveLock);
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}
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return handle;
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}
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/*
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* citus_update_node moves the requested node to a different nodename and nodeport. It
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* locks to ensure no queries are running concurrently; and is intended for customers who
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@ -1243,63 +1316,8 @@ citus_update_node(PG_FUNCTION_ARGS)
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EnsureTransactionalMetadataSyncMode();
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}
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/*
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* If the node is a primary node we block reads and writes.
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*
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* This lock has two purposes:
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*
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* - Ensure buggy code in Citus doesn't cause failures when the
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* nodename/nodeport of a node changes mid-query
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*
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* - Provide fencing during failover, after this function returns all
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* connections will use the new node location.
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*
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* Drawback:
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*
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* - This function blocks until all previous queries have finished. This
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* means that long-running queries will prevent failover.
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*
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* In case of node failure said long-running queries will fail in the end
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* anyway as they will be unable to commit successfully on the failed
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* machine. To cause quick failure of these queries use force => true
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* during the invocation of citus_update_node to terminate conflicting
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* backends proactively.
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*
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* It might be worth blocking reads to a secondary for the same reasons,
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* though we currently only query secondaries on follower clusters
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* where these locks will have no effect.
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*/
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if (NodeIsPrimary(workerNode))
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{
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/*
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* before acquiring the locks check if we want a background worker to help us to
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* aggressively obtain the locks.
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*/
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if (force)
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{
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handle = StartLockAcquireHelperBackgroundWorker(MyProcPid, lock_cooldown);
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if (!handle)
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{
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/*
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* We failed to start a background worker, which probably means that we exceeded
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* max_worker_processes, and this is unlikely to be resolved by retrying. We do not want
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* to repeatedly throw an error because if citus_update_node is called to complete a
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* failover then finishing is the only way to bring the cluster back up. Therefore we
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* give up on killing other backends and simply wait for the lock. We do set
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* lock_timeout to lock_cooldown, because we don't want to wait forever to get a lock.
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*/
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SetLockTimeoutLocally(lock_cooldown);
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ereport(WARNING, (errmsg(
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"could not start background worker to kill backends with conflicting"
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" locks to force the update. Degrading to acquiring locks "
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"with a lock time out."),
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errhint(
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"Increasing max_worker_processes might help.")));
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}
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}
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LockShardsInWorkerPlacementList(workerNode, AccessExclusiveLock);
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}
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handle = LockPlacementsWithBackgroundWorkersInPrimaryNode(workerNode, force,
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lock_cooldown);
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/*
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* if we have planned statements such as prepared statements, we should clear the cache so that
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@ -1358,6 +1376,8 @@ citus_pause_node_within_txn(PG_FUNCTION_ARGS)
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CheckCitusVersion(ERROR);
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int32 nodeId = PG_GETARG_INT32(0);
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bool force = PG_GETARG_BOOL(1);
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int32 lock_cooldown = PG_GETARG_INT32(2);
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WorkerNode *workerNode = FindNodeAnyClusterByNodeId(nodeId);
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if (workerNode == NULL)
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@ -1366,10 +1386,7 @@ citus_pause_node_within_txn(PG_FUNCTION_ARGS)
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errmsg("node %u not found", nodeId)));
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}
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if (NodeIsPrimary(workerNode))
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{
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LockShardsInWorkerPlacementList(workerNode, AccessExclusiveLock);
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}
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LockPlacementsWithBackgroundWorkersInPrimaryNode(workerNode, force, lock_cooldown);
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PG_RETURN_VOID();
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}
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@ -1992,7 +2009,8 @@ ErrorIfNodeContainsNonRemovablePlacements(WorkerNode *workerNode)
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ereport(ERROR, (errmsg("cannot remove or disable the node "
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"%s:%d because because it contains "
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"the only shard placement for "
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"shard " UINT64_FORMAT, workerNode->workerName,
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"shard " UINT64_FORMAT,
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workerNode->workerName,
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workerNode->workerPort, placement->shardId),
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errdetail("One of the table(s) that prevents the operation "
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"complete successfully is %s",
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@ -2544,7 +2562,8 @@ ErrorIfCoordinatorMetadataSetFalse(WorkerNode *workerNode, Datum value, char *fi
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if (!valueBool && workerNode->groupId == COORDINATOR_GROUP_ID)
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{
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ereport(ERROR, (errmsg("cannot change \"%s\" field of the "
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"coordinator node", field)));
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"coordinator node",
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field)));
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}
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}
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