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FAQ: update slow log, DDL and Syncer related questions #854
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@@ -257,6 +257,8 @@ You can use Docker Compose to build a TiDB cluster locally, including the cluste | |||||
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2. If a slow query occurs, you can locate the `tidb-server` instance where the slow query is and the slow query time point using Grafana and find the SQL statement information recorded in the log on the corresponding node. | ||||||
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3. Besides the log, you can also view the slow query using the `admin show slow` command. For details, see [`admin show slow` command](sql/slow-query.md#admin-show-slow-command). | ||||||
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#### How to add the `label` configuration if `label` of TiKV was not configured when I deployed the TiDB cluster for the first time? | ||||||
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The configuration of TiDB `label` is related to the cluster deployment architecture. It is important and is the basis for PD to execute global management and scheduling. If you did not configure `label` when deploying the cluster previously, you should adjust the deployment structure by manually adding the `location-labels` information using the PD management tool `pd-ctl`, for example, `config set location-labels "zone, rack, host"` (you should configure it based on the practical `label` level name). | ||||||
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@@ -749,6 +751,10 @@ CREATE TABLE if not exists mysql.user ( | |||||
INSERT INTO mysql.user VALUES ("%", "root", "", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y"); | ||||||
``` | ||||||
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#### 4.1.5 Can TiDB provide services while Loader is running? | ||||||
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There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. We do not use the heading number in English FAQ :) |
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Since Loader inserts the data logically, TiDB can provide services while it's running. But do not perform the related DDL operations. | ||||||
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#### How to export the data in TiDB? | ||||||
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Currently, TiDB does not support `select into outfile`. You can use the following methods to export the data in TiDB: | ||||||
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@@ -788,6 +794,10 @@ Two solutions: | |||||
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- You can also increase the limited number of statements in a single TiDB transaction, but this will consume more memory. | ||||||
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#### Does TiDB have a function like the Flashback Query in Oracle? Does it support DDL? | ||||||
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Yes, it does. And it supports DDL as well. For details, see [how TiDB reads data from history versions](op-guide/history-read.md). | ||||||
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### Migrate the data online | ||||||
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#### Syncer | ||||||
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@@ -829,6 +839,11 @@ Two solutions: | |||||
- Put the `syncer.meta` file in a relatively secure disk. For example, use disks with RAID 1. | ||||||
- Restore the location information of history synchronization according to the monitoring data that Syncer reports to Prometheus regularly. But the location information might be inaccurate due to the delay when a large amount of data is synchronized. | ||||||
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##### If the downstream TiDB data is not consistent with the MySQL data during Syncer's synchronization process, will DML operations cause exits? | ||||||
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- If data exists in the upstream MySQL and doesn't exist in the downstream TiDB, and the upstream MySQL performs the `UPDATE` or `DELETE` operation on this piece of data, it will not cause errors or exits and the data will not exist during Syncer's synchronization process. | ||||||
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- If conflicts exist in the primary key indexes or the unique indexes in the downstream, preforming `UPDATE` will cause exits while performing `INSERT` will not. | ||||||
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### Migrate the traffic | ||||||
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#### How to migrate the traffic quickly? | ||||||
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Please try to avoid using the word "besides". Reference: #505