system.metrics

### MergeJoinBlocksCacheCount[​](#mergejoinblockscachecount "Direct link to MergeJoinBlocksCacheCount")

Total cached blocks in MergeJoin

### MergeParts[​](#mergeparts "Direct link to MergeParts")

Number of source parts participating in current background merges

### MergeTreeAllRangesAnnouncementsSent[​](#mergetreeallrangesannouncementssent "Direct link to MergeTreeAllRangesAnnouncementsSent")

The current number of announcement being sent in flight from the remote server to the initiator server about the set of data parts (for MergeTree tables). Measured on the remote server side.

### MergeTreeBackgroundExecutorThreads[​](#mergetreebackgroundexecutorthreads "Direct link to MergeTreeBackgroundExecutorThreads")

Number of threads in the MergeTreeBackgroundExecutor thread pool.

### MergeTreeBackgroundExecutorThreadsActive[​](#mergetreebackgroundexecutorthreadsactive "Direct link to MergeTreeBackgroundExecutorThreadsActive")

Number of threads in the MergeTreeBackgroundExecutor thread pool running a task.

### MergeTreeBackgroundExecutorThreadsScheduled[​](#mergetreebackgroundexecutorthreadsscheduled "Direct link to MergeTreeBackgroundExecutorThreadsScheduled")

Number of queued or active jobs in the MergeTreeBackgroundExecutor thread pool.

### MergeTreeDataSelectExecutorThreads[​](#mergetreedataselectexecutorthreads "Direct link to MergeTreeDataSelectExecutorThreads")

Number of threads in the MergeTreeDataSelectExecutor thread pool.

### MergeTreeDataSelectExecutorThreadsActive[​](#mergetreedataselectexecutorthreadsactive "Direct link to MergeTreeDataSelectExecutorThreadsActive")

Number of threads in the MergeTreeDataSelectExecutor thread pool running a task.

### MergeTreeDataSelectExecutorThreadsScheduled[​](#mergetreedataselectexecutorthreadsscheduled "Direct link to MergeTreeDataSelectExecutorThreadsScheduled")

Number of queued or active jobs in the MergeTreeDataSelectExecutor thread pool.

### MergeTreeFetchPartitionThreads[​](#mergetreefetchpartitionthreads "Direct link to MergeTreeFetchPartitionThreads")

Number of threads for ALTER TABLE FETCH PARTITION

### MergeTreeFetchPartitionThreadsActive[​](#mergetreefetchpartitionthreadsactive "Direct link to MergeTreeFetchPartitionThreadsActive")

Number of threads for ALTER TABLE FETCH PARTITION fetching part

### MergeTreeFetchPartitionThreadsScheduled[​](#mergetreefetchpartitionthreadsscheduled "Direct link to MergeTreeFetchPartitionThreadsScheduled")

Number of queued or active part fetches in ALTER TABLE FETCH PARTITION

### MergeTreeOutdatedPartsLoaderThreads[​](#mergetreeoutdatedpartsloaderthreads "Direct link to MergeTreeOutdatedPartsLoaderThreads")

Number of threads in the threadpool for loading Outdated data parts.

### MergeTreeOutdatedPartsLoaderThreadsActive[​](#mergetreeoutdatedpartsloaderthreadsactive "Direct link to MergeTreeOutdatedPartsLoaderThreadsActive")

Number of active threads in the threadpool for loading Outdated data parts.

### MergeTreeOutdatedPartsLoaderThreadsScheduled[​](#mergetreeoutdatedpartsloaderthreadsscheduled "Direct link to MergeTreeOutdatedPartsLoaderThreadsScheduled")

Number of queued or active jobs in the threadpool for loading Outdated data parts.

### MergeTreePartsCleanerThreads[​](#mergetreepartscleanerthreads "Direct link to MergeTreePartsCleanerThreads")

Number of threads in the MergeTree parts cleaner thread pool.

### MergeTreePartsCleanerThreadsActive[​](#mergetreepartscleanerthreadsactive "Direct link to MergeTreePartsCleanerThreadsActive")

Number of threads in the MergeTree parts cleaner thread pool running a task.

### MergeTreePartsCleanerThreadsScheduled[​](#mergetreepartscleanerthreadsscheduled "Direct link to MergeTreePartsCleanerThreadsScheduled")

Number of queued or active jobs in the MergeTree parts cleaner thread pool.

### MergeTreePartsLoaderThreads[​](#mergetreepartsloaderthreads "Direct link to MergeTreePartsLoaderThreads")

Number of threads in the MergeTree parts loader thread pool.

### MergeTreePartsLoaderThreadsActive[​](#mergetreepartsloaderthreadsactive "Direct link to MergeTreePartsLoaderThreadsActive")

Number of threads in the MergeTree parts loader thread pool running a task.

### MergeTreePartsLoaderThreadsScheduled[​](#mergetreepartsloaderthreadsscheduled "Direct link to MergeTreePartsLoaderThreadsScheduled")

Number of queued or active jobs in the MergeTree parts loader thread pool.

### MergeTreeReadTaskRequestsSent[​](#mergetreereadtaskrequestssent "Direct link to MergeTreeReadTaskRequestsSent")

The current number of callback requests in flight from the remote server back to the initiator server to choose the read task (for MergeTree tables). Measured on the remote server side.

### MergeTreeSnapshotCommitThreads[​](#mergetreesnapshotcommitthreads "Direct link to MergeTreeSnapshotCommitThreads")

Number of threads used to commit snapshot

### MergeTreeSnapshotCommitThreadsActive[​](#mergetreesnapshotcommitthreadsactive "Direct link to MergeTreeSnapshotCommitThreadsActive")

Number of active threads used to commit snapshot

### MergeTreeSnapshotCommitThreadsScheduled[​](#mergetreesnapshotcommitthreadsscheduled "Direct link to MergeTreeSnapshotCommitThreadsScheduled")

Number of scheduled threads used to commit snapshot

### MergeTreeSubcolumnsReaderThreads[​](#mergetreesubcolumnsreaderthreads "Direct link to MergeTreeSubcolumnsReaderThreads")

Number of threads in the thread pool used for subcolumns reading in MergeTree.

### MergeTreeSubcolumnsReaderThreadsActive[​](#mergetreesubcolumnsreaderthreadsactive "Direct link to MergeTreeSubcolumnsReaderThreadsActive")

Number of threads in the thread pool used for subcolumns reading in MergeTree running a task.

### MergeTreeSubcolumnsReaderThreadsScheduled[​](#mergetreesubcolumnsreaderthreadsscheduled "Direct link to MergeTreeSubcolumnsReaderThreadsScheduled")

Number of queued or active jobs in the thread pool used for subcolumns reading in MergeTree.

### MergeTreeUnexpectedPartsLoaderThreads[​](#mergetreeunexpectedpartsloaderthreads "Direct link to MergeTreeUnexpectedPartsLoaderThreads")

Number of threads in the threadpool for loading Unexpected data parts.

### MergeTreeUnexpectedPartsLoaderThreadsActive[​](#mergetreeunexpectedpartsloaderthreadsactive "Direct link to MergeTreeUnexpectedPartsLoaderThreadsActive")

Number of active threads in the threadpool for loading Unexpected data parts.

### MergeTreeUnexpectedPartsLoaderThreadsScheduled[​](#mergetreeunexpectedpartsloaderthreadsscheduled "Direct link to MergeTreeUnexpectedPartsLoaderThreadsScheduled")

Number of queued or active jobs in the threadpool for loading Unexpected data parts.

### MergesMutationsMemoryTracking[​](#mergesmutationsmemorytracking "Direct link to MergesMutationsMemoryTracking")

Total amount of memory (bytes) allocated by background tasks (merges and mutations).

### MetadataFromKeeperCacheObjects[​](#metadatafromkeepercacheobjects "Direct link to MetadataFromKeeperCacheObjects")

Number of objects in disk metadata cache.

### Move[​](#move "Direct link to Move")

Number of currently executing moves

### MySQLConnection[​](#mysqlconnection "Direct link to MySQLConnection")

Number of client connections using MySQL protocol

### NamedCollection[​](#namedcollection "Direct link to NamedCollection")

Number of named collections

### NetworkReceive[​](#networkreceive "Direct link to NetworkReceive")

Number of threads receiving data from network. Only ClickHouse-related network interaction is included, not by 3rd party libraries.

### NetworkSend[​](#networksend "Direct link to NetworkSend")

Number of threads sending data to network. Only ClickHouse-related network interaction is included, not by 3rd party libraries.

### ObjectStorageAzureThreads[​](#objectstorageazurethreads "Direct link to ObjectStorageAzureThreads")

Number of threads in the AzureObjectStorage thread pool.

### ObjectStorageAzureThreadsActive[​](#objectstorageazurethreadsactive "Direct link to ObjectStorageAzureThreadsActive")

Number of threads in the AzureObjectStorage thread pool running a task.