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Mar 7, 2023
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sql-faq: add missing DELAYED priority (#12237) #12790

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sql-faq: add missing DELAYED priority
dveeden Jan 27, 2023
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Update faq/sql-faq.md
dveeden Jan 27, 2023
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Update faq/sql-faq.md
shichun-0415 Mar 7, 2023
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14 changes: 8 additions & 6 deletions faq/sql-faq.md
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Expand Up @@ -205,21 +205,23 @@ TiDB supports changing the priority on a [global](/system-variables.md#tidb_forc

- `LOW_PRIORITY`: this statement has a low priority, that is, TiDB reduces the priority of this statement during the execution period.

- `DELAYED`: this statement has normal priority and is the same as the `NO_PRIORITY` setting for `tidb_force_priority`.

You can combine the above two parameters with the DML of TiDB to use them. For example:

1. Adjust the priority by writing SQL statements in the database:

{{< copyable "sql" >}}

```sql
select HIGH_PRIORITY | LOW_PRIORITY count(*) from table_name;
insert HIGH_PRIORITY | LOW_PRIORITY into table_name insert_values;
delete HIGH_PRIORITY | LOW_PRIORITY from table_name;
update HIGH_PRIORITY | LOW_PRIORITY table_reference set assignment_list where where_condition;
replace HIGH_PRIORITY | LOW_PRIORITY into table_name;
SELECT HIGH_PRIORITY | LOW_PRIORITY | DELAYED COUNT(*) FROM table_name;
INSERT HIGH_PRIORITY | LOW_PRIORITY | DELAYED INTO table_name insert_values;
DELETE HIGH_PRIORITY | LOW_PRIORITY | DELAYED FROM table_name;
UPDATE HIGH_PRIORITY | LOW_PRIORITY | DELAYED table_reference SET assignment_list WHERE where_condition;
REPLACE HIGH_PRIORITY | LOW_PRIORITY | DELAYED INTO table_name;
```

2. The full table scan statement automatically adjusts itself to a low priority. `analyze` has a low priority by default.
2. The full table scan statement automatically adjusts itself to a low priority. [`ANALYZE`](/sql-statements/sql-statement-analyze-table.md) has a low priority by default.

## What's the trigger strategy for `auto analyze` in TiDB?

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