· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 1882 17 11.2.6 TiKV MVCC In-Memory Engine· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 1885 11.2.7 Tune · · · · · · · · · · · · · · · · · · · · · · · · · 6726 17.10.2 Multi-version concurrency control (MVCC) · · · · · · · · · · · · · · · · · · · · · · · · 6726 17.11 O · · · · · · · · · · · · · · · · · · to help you troubleshoot errors. 4.11.3.1 GC timeout TiDB’s transaction implementation uses the MVCC (Multiple Version Concurrency Con- trol) mechanism. When the newly written data overwrites the old

�→ ts.scan �→ -lock- �→ pool- �→ size Newly added The number of threads that TiKV uses to scan the MVCC (multi- version concurrency control) lock data when initializing the resolved- �→ ts. The default scheduler-pending �→ -write-threshold (100MB). You can verify the cause by viewing the metric corresponding to MVCC_CONFLICT_COUNTER. – Slow write causes write tasks to pile up. The data being written to TiKV ex- Coprocessor has processed. Compared with total_keys, processed_keys does not include the old versions of MVCC. A great difference between processed_keys and total_keys indicates that many old versions exist.

the cgroup information from some platforms #10980 – Fix the issue of poor scan performance because MVCC Deletion versions are not dropped by compaction filter GC #11248 • PD – Fix the issue that PD incorrectly scheduler-pending �→ -write-threshold (100MB). You can verify the cause by viewing the metric corresponding to MVCC_CONFLICT_COUNTER. – Slow write causes write tasks to pile up. The data being written to TiKV ex- Coprocessor has processed. Compared with total_keys, processed_keys does not include the old versions of MVCC. A great difference between processed_keys and total_keys indicates that many old versions exist.

scheduler-pending �→ -write-threshold (100MB). You can verify the cause by viewing the metric corresponding to MVCC_CONFLICT_COUNTER. – Slow write causes write tasks to pile up. The data being written to TiKV ex- Coprocessor has processed. Compared with total_keys, processed_keys does not include the old versions of MVCC. A great difference between processed_keys and total_keys indicates that many old versions exist. Coprocessor has processed. Compared with total_keys, processed_keys does not include the old versions of MVCC. A great difference between processed_keys and total_keys indicates that many old versions exist.

region �→ - �→ compact �→ -min �→ - �→ redundant �→ - �→ rows Modified Sets the number of redun- dant MVCC rows required to trigger RocksDB com- paction. Starting from v7.5.0, this configu- ration item takes compact �→ - �→ redundant �→ - �→ rows �→ - �→ percent �→ Modified Sets the percent- age of redun- dant MVCC rows required to trigger RocksDB com- paction. Starting from v7.5.0, this configu- ration item takes to help you troubleshoot errors. 4.10.3.1 GC timeout TiDB’s transaction implementation uses the MVCC (Multiple Version Concurrency Con- trol) mechanism. When the newly written data overwrites the old

to help you troubleshoot errors. 4.10.3.1 GC timeout TiDB’s transaction implementation uses the MVCC (Multiple Version Concurrency Con- trol) mechanism. When the newly written data overwrites the old periodic Garbage Collection (GC) to clean up the old data that is no longer needed. By default, each MVCC version (consistency snapshots) is kept for 10 minutes. Trans- actions that take longer than 10 minutes snapshots), you can adjust the value of tikv_gc_life_time in the mysql.tidb table in TiDB to increase the MVCC version retention time. Note that tikv_gc_life_time takes effect globally and immediately. Increasing

region- �→ compact �→ -min �→ - �→ redundant �→ - �→ rows Newly added Sets the number of redun- dant MVCC rows required to trigger RocksDB com- paction. The default value is 50000. TiKV region- �→ compact �→ - �→ redundant �→ - �→ rows �→ - �→ percent �→ Newly added Sets the percent- age of redun- dant MVCC rows required to trigger RocksDB com- paction. The default value is 20. 70 Configuration file Configuration to help you troubleshoot errors. 4.10.3.1 GC timeout TiDB’s transaction implementation uses the MVCC (Multiple Version Concurrency Con- trol) mechanism. When the newly written data overwrites the old

INDEX HASH JOIN returns the send on closed channel error #31129 • TiKV – Fix the issue that the MVCC deletion records are not cleared by GC #11217 – Fix the issue that retrying prewrite requests in the scheduler-pending �→ -write-threshold (100MB). You can verify the cause by viewing the metric corresponding to MVCC_CONFLICT_COUNTER. – Slow write causes write tasks to pile up. The data being written to TiKV ex- Coprocessor has processed. Compared with total_keys, processed_keys does not include the old versions of MVCC. A great difference between processed_keys and total_keys indicates that many old versions exist.

· · · · · · · · · · · · · · · · · · · · · · · · · 6702 17.7.2 Multi-version concurrency control (MVCC) · · · · · · · · · · · · · · · · · · · · · · · · 6702 17.8 O · · · · · · · · · · · · · · · · · · to help you troubleshoot errors. 4.11.3.1 GC timeout TiDB’s transaction implementation uses the MVCC (Multiple Version Concurrency Con- trol) mechanism. When the newly written data overwrites the old old data that is no longer needed. • For TiDB versions earlier than v4.0: 626 By default, each MVCC version (consistency snapshots) is kept for 10 minutes. Trans- actions that take longer than 10 minutes

configuring the maximum GC wait time The transaction of TiDB adopts the Multi-Version Concurrency Control (MVCC) mech- anism. When the newly written data overwrites the old data, the old data is not replaced, and provides a new Raw Key Value storage format and access interface, including: • The data is stored in MVCC and the change timestamp of the data is recorded. This feature will lay the foundation for implementing to help you troubleshoot errors. 4.10.3.1 GC timeout TiDB’s transaction implementation uses the MVCC (Multiple Version Concurrency Con- trol) mechanism. When the newly written data overwrites the old