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functions-and-operators, releases: clarify TIDB_DECODE_SQL_DIGESTS wording #23686

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functions-and-operators, releases: clarify TIDB_DECODE_SQL_DIGESTS wo…
yahonda Sep 1, 2026
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Update functions-and-operators/tidb-functions.md
yahonda Sep 3, 2026
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Update functions-and-operators/tidb-functions.md
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Update releases/release-5.2.0.md
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Update functions-and-operators/tidb-functions.md
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6 changes: 3 additions & 3 deletions functions-and-operators/tidb-functions.md
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Expand Up @@ -17,7 +17,7 @@ The following functions are TiDB extensions, and are not present in MySQL:
| [`TIDB_DECODE_BINARY_PLAN()`](#tidb_decode_binary_plan) | Decodes binary plans. |
| [`TIDB_DECODE_KEY()`](#tidb_decode_key) | Decodes a TiDB-encoded key entry into a JSON structure containing `_tidb_rowid` and `table_id`. These encoded keys can be found in some system tables and logging outputs. |
| [`TIDB_DECODE_PLAN()`](#tidb_decode_plan) | Decodes a TiDB execution plan. |
| [`TIDB_DECODE_SQL_DIGESTS()`](#tidb_decode_sql_digests) | Queries the normalized SQL statements (a form without formats and arguments) corresponding to a set of SQL digests in the cluster. |
| [`TIDB_DECODE_SQL_DIGESTS()`](#tidb_decode_sql_digests) | Queries the normalized SQL statements (in which literal values are replaced with placeholders such as `?` or `...`) corresponding to a set of SQL digests in the cluster. |
| [`TIDB_ENCODE_INDEX_KEY()`](#tidb_encode_index_key) | Encodes an index key. |
| [`TIDB_ENCODE_RECORD_KEY()`](#tidb_encode_record_key) | Encodes a record key. |
| [`TIDB_ENCODE_SQL_DIGEST()`](#tidb_encode_sql_digest) | Gets a digest for a query string. |
Expand All @@ -42,7 +42,7 @@ The following functions are TiDB extensions, and are not present in MySQL:
| [`TIDB_DECODE_BINARY_PLAN()`](#tidb_decode_binary_plan) | Decodes binary plans. |
| [`TIDB_DECODE_KEY()`](#tidb_decode_key) | Decodes a TiDB-encoded key entry into a JSON structure containing `_tidb_rowid` and `table_id`. These encoded keys can be found in some system tables and logging outputs. |
| [`TIDB_DECODE_PLAN()`](#tidb_decode_plan) | Decodes a TiDB execution plan. |
| [`TIDB_DECODE_SQL_DIGESTS()`](#tidb_decode_sql_digests) | Queries the normalized SQL statements (a form without formats and arguments) corresponding to a set of SQL digests in the cluster. |
| [`TIDB_DECODE_SQL_DIGESTS()`](#tidb_decode_sql_digests) | Queries the normalized SQL statements (in which literal values are replaced with placeholders such as `?` or `...`) corresponding to a set of SQL digests in the cluster. |
| [`TIDB_ENCODE_INDEX_KEY()`](#tidb_encode_index_key) | Encodes an index key. |
| [`TIDB_ENCODE_RECORD_KEY()`](#tidb_encode_record_key) | Encodes a record key. |
| [`TIDB_ENCODE_SQL_DIGEST()`](#tidb_encode_sql_digest) | Gets a digest for a query string. |
Expand Down Expand Up @@ -294,7 +294,7 @@ SELECT tidb_decode_plan('8QIYMAkzMV83CQEH8E85LjA0CWRhdGE6U2VsZWN0aW9uXzYJOTYwCXR

## TIDB_DECODE_SQL_DIGESTS

The `TIDB_DECODE_SQL_DIGESTS()` function is used to query the normalized SQL statements (a form without formats and arguments) corresponding to the set of SQL digests in the cluster. This function accepts 1 or 2 arguments:
The `TIDB_DECODE_SQL_DIGESTS()` function is used to query the normalized SQL statements (in which literal values are replaced with placeholders such as `?` or `...`) corresponding to the set of SQL digests in the cluster. This function accepts 1 or 2 arguments:

* `digests`: A string. This parameter is in the format of a JSON string array, and each string in the array is a SQL digest.
* `stmtTruncateLength`: An integer (optional). It is used to limit the length of each SQL statement in the returned result. If a SQL statement exceeds the specified length, the statement is truncated. `0` means that the length is unlimited.
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2 changes: 1 addition & 1 deletion releases/release-5.2.0.md
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Expand Up @@ -112,7 +112,7 @@ In v5.2, the key new features and improvements are as follows:
In v5.2, the following enhancements are made to Lock View:

- In addition to the SQL digest column in the Lock View-related tables, add a column to these tables that shows the corresponding normalized SQL text. You do not have to manually query the statement corresponding to a SQL digest.
- Add the `TIDB_DECODE_SQL_DIGESTS` function to query the normalized SQL statements (a form without formats and arguments) corresponding to a set of SQL digests in the cluster. This simplifies the operation of querying the statements that have been historically executed by a transaction.
- Add the `TIDB_DECODE_SQL_DIGESTS` function to query the normalized SQL statements (in which literal values are replaced with placeholders such as `?` or `...`) corresponding to a set of SQL digests in the cluster. This simplifies the operation of querying the statements that have been historically executed by a transaction.
- Add a column in the `DATA_LOCK_WAITS` and `DEADLOCKS` system tables to show the table name, row ID, index value, and other key information interpreted from a key. This simplifies the operations such as locating the table to which a key belongs and interpreting the key information.
- Support collecting the information of retryable deadlock errors in the `DEADLOCKS` table, which makes it easier to troubleshoot issues caused by such errors. The error collection is disabled by default and can be enabled using the `pessimistic-txn.deadlock-history-collect-retryable` configuration.
- Support distinguishing query-executing transactions from idle transactions on the `TIDB_TRX` system table. The `Normal` state is now divided into `Running` and `Idle` states.
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