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updated SQL for DATA_LENGTH (#15432) (#15434)
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‎dm/dm-hardware-and-software-requirements.md

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@@ -56,18 +56,31 @@ The target TiKV cluster must have enough disk space to store the imported data.
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You can estimate the data volume by using the following SQL statements to summarize the `DATA_LENGTH` field:
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- Calculate the size of all schemas, in MiB. Replace `${schema_name}` with your schema name.
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{{< copyable "sql" >}}
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```sql
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select table_schema,sum(data_length)/1024/1024 as data_length,sum(index_length)/1024/1024 as index_length,sum(data_length+index_length)/1024/1024 as sum from information_schema.tables where table_schema = "${schema_name}" group by table_schema;
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```
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- Calculate the size of the largest table, in MiB. Replace ${schema_name} with your schema name.
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{{< copyable "sql" >}}
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```sql
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select table_name,table_schema,sum(data_length)/1024/1024 as data_length,sum(index_length)/1024/1024 as index_length,sum(data_length+index_length)/1024/1024 as sum from information_schema.tables where table_schema = "${schema_name}" group by table_name,table_schema order by sum desc limit 5;
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```
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```sql
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-- Calculate the size of all schemas
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SELECT
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TABLE_SCHEMA,
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FORMAT_BYTES(SUM(DATA_LENGTH)) AS 'Data Size',
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FORMAT_BYTES(SUM(INDEX_LENGTH)) 'Index Size'
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FROM
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information_schema.tables
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GROUP BY
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TABLE_SCHEMA;
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-- Calculate the 5 largest tables
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SELECT
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TABLE_NAME,
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TABLE_SCHEMA,
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FORMAT_BYTES(SUM(data_length)) AS 'Data Size',
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FORMAT_BYTES(SUM(index_length)) AS 'Index Size',
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FORMAT_BYTES(SUM(data_length+index_length)) AS 'Total Size'
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FROM
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information_schema.tables
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GROUP BY
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TABLE_NAME,
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TABLE_SCHEMA
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ORDER BY
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SUM(DATA_LENGTH+INDEX_LENGTH) DESC
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LIMIT
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5;
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```

‎migrate-large-mysql-to-tidb.md

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@@ -31,14 +31,33 @@ This document describes how to perform the full migration using Dumpling and TiD
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**Note**: It is difficult to calculate the exact data volume exported by Dumpling from MySQL, but you can estimate the data volume by using the following SQL statement to summarize the `DATA_LENGTH` field in the `information_schema.tables` table:
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{{< copyable "" >}}
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```sql
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/* Calculate the size of all schemas, in MiB. Replace ${schema_name} with your schema name. */
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SELECT table_schema,SUM(data_length)/1024/1024 AS data_length,SUM(index_length)/1024/1024 AS index_length,SUM(data_length+index_length)/1024/1024 AS SUM FROM information_schema.tables WHERE table_schema = "${schema_name}" GROUP BY table_schema;
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/* Calculate the size of the largest table, in MiB. Replace ${schema_name} with your schema name. */
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SELECT table_name,table_schema,SUM(data_length)/1024/1024 AS data_length,SUM(index_length)/1024/1024 AS index_length,SUM(data_length+index_length)/1024/1024 AS SUM from information_schema.tables WHERE table_schema = "${schema_name}" GROUP BY table_name,table_schema ORDER BY SUM DESC LIMIT 5;
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-- Calculate the size of all schemas
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SELECT
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TABLE_SCHEMA,
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FORMAT_BYTES(SUM(DATA_LENGTH)) AS 'Data Size',
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FORMAT_BYTES(SUM(INDEX_LENGTH)) 'Index Size'
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FROM
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information_schema.tables
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GROUP BY
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TABLE_SCHEMA;
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-- Calculate the 5 largest tables
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SELECT
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TABLE_NAME,
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TABLE_SCHEMA,
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FORMAT_BYTES(SUM(data_length)) AS 'Data Size',
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FORMAT_BYTES(SUM(index_length)) AS 'Index Size',
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FORMAT_BYTES(SUM(data_length+index_length)) AS 'Total Size'
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FROM
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information_schema.tables
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GROUP BY
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TABLE_NAME,
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TABLE_SCHEMA
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ORDER BY
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SUM(DATA_LENGTH+INDEX_LENGTH) DESC
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LIMIT
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5;
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```
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### Disk space for the target TiKV cluster

‎tidb-lightning/tidb-lightning-requirements.md

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Original file line numberDiff line numberDiff line change
@@ -86,16 +86,31 @@ The target TiKV cluster must have enough disk space to store the imported data.
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It is difficult to calculate the exact data volume exported by Dumpling from MySQL. However, you can estimate the data volume by using the following SQL statement to summarize the `DATA_LENGTH` field in the information_schema.tables table:
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Calculate the size of all schemas, in MiB. Replace ${schema_name} with your schema name.
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```sql
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SELECT table_schema, SUM(data_length)/1024/1024 AS data_length, SUM(index_length)/1024/1024 AS index_length, SUM(data_length+index_length)/1024/1024 AS sum FROM information_schema.tables WHERE table_schema = "${schema_name}" GROUP BY table_schema;
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```
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Calculate the size of the largest table, in MiB. Replace ${schema_name} with your schema name.
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-- Calculate the size of all schemas
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SELECT
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TABLE_SCHEMA,
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FORMAT_BYTES(SUM(DATA_LENGTH)) AS 'Data Size',
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FORMAT_BYTES(SUM(INDEX_LENGTH)) 'Index Size'
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FROM
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information_schema.tables
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GROUP BY
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TABLE_SCHEMA;
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{{< copyable "sql" >}}
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```sql
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SELECT table_name, table_schema, SUM(data_length)/1024/1024 AS data_length, SUM(index_length)/1024/1024 AS index_length,sum(data_length+index_length)/1024/1024 AS sum FROM information_schema.tables WHERE table_schema = "${schema_name}" GROUP BY table_name,table_schema ORDER BY sum DESC LIMIT 5;
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-- Calculate the 5 largest tables
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SELECT
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TABLE_NAME,
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TABLE_SCHEMA,
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FORMAT_BYTES(SUM(data_length)) AS 'Data Size',
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FORMAT_BYTES(SUM(index_length)) AS 'Index Size',
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FORMAT_BYTES(SUM(data_length+index_length)) AS 'Total Size'
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FROM
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information_schema.tables
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GROUP BY
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TABLE_NAME,
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TABLE_SCHEMA
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ORDER BY
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SUM(DATA_LENGTH+INDEX_LENGTH) DESC
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LIMIT
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5;
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```

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