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Simplify metadata lock acquisition for DML

pull/1474/head
Marco Slot 2017-07-03 14:17:10 +02:00
parent aa7ca81548
commit 4cc7c36596
3 changed files with 22 additions and 49 deletions
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45
src/backend/distributed/executor/multi_router_executor.c
View File

@ -73,7 +73,7 @@ bool AllModificationsCommutative = false;
bool EnableDeadlockPrevention = true;
/* functions needed during run phase */
static void ReacquireMetadataLocks(List *taskList);
static void AcquireMetadataLocks(List *taskList);
static ShardPlacementAccess * CreatePlacementAccess(ShardPlacement *placement,
ShardPlacementAccessType accessType);
static void ExecuteSingleModifyTask(CitusScanState *scanState, Task *task,
@ -100,22 +100,12 @@ static bool ConsumeQueryResult(MultiConnection *connection, bool failOnError,
/*
* ReacquireMetadataLocks re-acquires the metadata locks that are normally
* acquired during planning.
*
* If we are executing a prepared statement, then planning might have
* happened in a separate transaction and advisory locks are no longer
* held. If a shard is currently being repaired/copied/moved, then
* obtaining the locks will fail and this function throws an error to
* prevent executing a stale plan.
*
* If we are executing a non-prepared statement or planning happened in
* the same transaction, then we already have the locks and obtain them
* again here. Since we always release these locks at the end of the
* transaction, this is effectively a no-op.
* AcquireMetadataLocks acquires metadata locks on each of the anchor
* shards in the task list to prevent a shard being modified while it
* is being copied.
*/
static void
ReacquireMetadataLocks(List *taskList)
AcquireMetadataLocks(List *taskList)
{
ListCell *taskCell = NULL;
@ -130,28 +120,7 @@ ReacquireMetadataLocks(List *taskList)
{
Task *task = (Task *) lfirst(taskCell);
/*
* Only obtain metadata locks for modifications to allow reads to
* proceed during shard copy.
*/
if (task->taskType == MODIFY_TASK &&
!TryLockShardDistributionMetadata(task->anchorShardId, ShareLock))
{
/*
* We could error out immediately to give quick feedback to the
* client, but this might complicate flow control and our default
* behaviour during shard copy is to block.
*
* Block until the lock becomes available such that the next command
* will likely succeed and use the serialization failure error code
* to signal to the client that it should retry the current command.
*/
LockShardDistributionMetadata(task->anchorShardId, ShareLock);
ereport(ERROR, (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
errmsg("prepared modifications cannot be executed on "
"a shard while it is being copied")));
}
LockShardDistributionMetadata(task->anchorShardId, ShareLock);
}
}
@ -457,7 +426,7 @@ CitusModifyBeginScan(CustomScanState *node, EState *estate, int eflags)
}
/* prevent concurrent placement changes */
ReacquireMetadataLocks(taskList);
AcquireMetadataLocks(taskList);
/* assign task placements */
workerJob->taskList = FirstReplicaAssignTaskList(taskList);

20
src/test/regress/expected/isolation_dml_vs_repair.out
View File

@ -78,7 +78,7 @@ step s2-invalidate-57638:
UPDATE pg_dist_shard_placement SET shardstate = '3' WHERE shardid = (SELECT shardid FROM pg_dist_shard WHERE logicalrelid = 'test_dml_vs_repair'::regclass) AND nodeport = 57638;
step s1-display:
SELECT * FROM test_dml_vs_repair WHERE test_id = 1;
SELECT * FROM test_dml_vs_repair WHERE test_id = 1 ORDER BY test_id;
test_id data
@ -90,7 +90,7 @@ step s2-revalidate-57638:
UPDATE pg_dist_shard_placement SET shardstate = '1' WHERE shardid = (SELECT shardid FROM pg_dist_shard WHERE logicalrelid = 'test_dml_vs_repair'::regclass) AND nodeport = 57638;
step s1-display:
SELECT * FROM test_dml_vs_repair WHERE test_id = 1;
SELECT * FROM test_dml_vs_repair WHERE test_id = 1 ORDER BY test_id;
test_id data
@ -122,15 +122,15 @@ step s2-commit:
COMMIT;
step s1-prepared-insertone: <... completed>
error in steps s2-commit s1-prepared-insertone: ERROR: prepared modifications cannot be executed on a shard while it is being copied
step s2-invalidate-57638:
UPDATE pg_dist_shard_placement SET shardstate = '3' WHERE shardid = (SELECT shardid FROM pg_dist_shard WHERE logicalrelid = 'test_dml_vs_repair'::regclass) AND nodeport = 57638;
step s1-display:
SELECT * FROM test_dml_vs_repair WHERE test_id = 1;
SELECT * FROM test_dml_vs_repair WHERE test_id = 1 ORDER BY test_id;
test_id data
1 1
1 1
step s2-invalidate-57637:
UPDATE pg_dist_shard_placement SET shardstate = '3' WHERE shardid = (SELECT shardid FROM pg_dist_shard WHERE logicalrelid = 'test_dml_vs_repair'::regclass) AND nodeport = 57637;
@ -139,10 +139,11 @@ step s2-revalidate-57638:
UPDATE pg_dist_shard_placement SET shardstate = '1' WHERE shardid = (SELECT shardid FROM pg_dist_shard WHERE logicalrelid = 'test_dml_vs_repair'::regclass) AND nodeport = 57638;
step s1-display:
SELECT * FROM test_dml_vs_repair WHERE test_id = 1;
SELECT * FROM test_dml_vs_repair WHERE test_id = 1 ORDER BY test_id;
test_id data
1 1
1 1
starting permutation: s2-invalidate-57637 s1-insertone s1-prepared-insertall s2-begin s2-repair s1-prepared-insertall s2-commit s2-invalidate-57638 s1-display s2-invalidate-57637 s2-revalidate-57638 s1-display
@ -174,17 +175,18 @@ step s2-commit:
COMMIT;
step s1-prepared-insertall: <... completed>
error in steps s2-commit s1-prepared-insertall: ERROR: prepared modifications cannot be executed on a shard while it is being copied
step s2-invalidate-57638:
UPDATE pg_dist_shard_placement SET shardstate = '3' WHERE shardid = (SELECT shardid FROM pg_dist_shard WHERE logicalrelid = 'test_dml_vs_repair'::regclass) AND nodeport = 57638;
step s1-display:
SELECT * FROM test_dml_vs_repair WHERE test_id = 1;
SELECT * FROM test_dml_vs_repair WHERE test_id = 1 ORDER BY test_id;
test_id data
1 1
1 2
1 2
1 3
step s2-invalidate-57637:
UPDATE pg_dist_shard_placement SET shardstate = '3' WHERE shardid = (SELECT shardid FROM pg_dist_shard WHERE logicalrelid = 'test_dml_vs_repair'::regclass) AND nodeport = 57637;
@ -192,9 +194,11 @@ step s2-revalidate-57638:
UPDATE pg_dist_shard_placement SET shardstate = '1' WHERE shardid = (SELECT shardid FROM pg_dist_shard WHERE logicalrelid = 'test_dml_vs_repair'::regclass) AND nodeport = 57638;
step s1-display:
SELECT * FROM test_dml_vs_repair WHERE test_id = 1;
SELECT * FROM test_dml_vs_repair WHERE test_id = 1 ORDER BY test_id;
test_id data
1 1
1 2
1 2
1 3

6
src/test/regress/specs/isolation_dml_vs_repair.spec
View File

@ -47,7 +47,7 @@ step "s1-prepared-insertall"
step "s1-display"
{
SELECT * FROM test_dml_vs_repair WHERE test_id = 1;
SELECT * FROM test_dml_vs_repair WHERE test_id = 1 ORDER BY test_id;
}
step "s1-commit"
@ -102,8 +102,8 @@ permutation "s1-insertone" "s2-invalidate-57637" "s1-begin" "s1-insertall" "s2-r
# verify that modifications wait for shard repair
permutation "s2-invalidate-57637" "s2-begin" "s2-repair" "s1-insertone" "s2-commit" "s2-invalidate-57638" "s1-display" "s2-invalidate-57637" "s2-revalidate-57638" "s1-display"
# verify that prepared plain modifications wait for shard repair (and then fail to avoid race)
# verify that prepared plain modifications wait for shard repair
permutation "s2-invalidate-57637" "s1-prepared-insertone" "s2-begin" "s2-repair" "s1-prepared-insertone" "s2-commit" "s2-invalidate-57638" "s1-display" "s2-invalidate-57637" "s2-revalidate-57638" "s1-display"
# verify that prepared INSERT ... SELECT waits for shard repair (and then fail to avoid race)
# verify that prepared INSERT ... SELECT waits for shard repair
permutation "s2-invalidate-57637" "s1-insertone" "s1-prepared-insertall" "s2-begin" "s2-repair" "s1-prepared-insertall" "s2-commit" "s2-invalidate-57638" "s1-display" "s2-invalidate-57637" "s2-revalidate-57638" "s1-display"