Set Lindorm SQL Session Variables for Query Optimization - Lindorm

Session variables let you control SQL engine behavior on a per-connection basis. Changes take effect immediately for the current session and do not affect other sessions.

Prerequisites

Before you begin, ensure that you have:

Lindorm SQL version 2.8.4.0 or later. To check your version, see SQL versions.

Applicable engines

LindormTable and LindormTSDB (all versions).

Syntax

Set a session variable:

SET [SESSION] variable_identifier = literal

Query a session variable:

SELECT @@variable_identifier

Variable names follow the same lexical rules as common identifiers. For details, see Lexical structure of Lindorm SQL.

Session variables reference

Session-level parameters set by SET take precedence over global parameters set by ALTER SYSTEM. When the two conflict, the session-level value always wins.

Important

Modifying session-level parameters affects SQL engine behavior for the duration of the session. Understand each parameter before changing it.

TIME_ZONE

Attribute	Value
Data type	String
Default	`+08:00` (UTC+8)
Applicable engine	LindormTable
Protocol constraint	MySQL protocol only

Sets the time zone for the current session. Only available when connecting via the MySQL protocol.

SQL_MODE

Attribute	Value
Data type	String
Applicable engine	LindormTable, LindormTSDB
Introduced in	Lindorm SQL 2.8.4.8

Controls the SQL engine parsing behavior. To set multiple modes, separate them with a comma (,).

Only supported value:

NO_BACKSLASH_ESCAPES — Backslashes (\) are treated as literal characters rather than escape characters when parsing string literals.

Examples

Change the session time zone

Query the current session time zone:

SELECT @@TIME_ZONE;

Expected output:

+-------------+
| @@TIME_ZONE |
+-------------+
| +08:00      |
+-------------+

Change the time zone to UTC:
```
SET TIME_ZONE='UTC';
```

Verify the change:

SELECT @@TIME_ZONE;

Expected output:

+-------------+
| @@TIME_ZONE |
+-------------+
| UTC         |
+-------------+

Note

For details on how the session time zone affects timestamp data, see Specify a time zone for a LindormTable connection.

Disable backslash escaping

Query a string literal to observe the default escape behavior:

SELECT '{\"key\":\"va\\lu\'e\r\n\"}';

Expected output:

+---------------------+
| EXPR$0              |
+---------------------+
| {"key":"va\lu'e
"} |
+---------------------+

Set NO_BACKSLASH_ESCAPES to disable backslash escaping:
```
SET SQL_MODE='NO_BACKSLASH_ESCAPES';
```

Run the same query to verify the change:

SELECT '{\"key\":\"va\\lu\'e\r\n\"}';

Expected output:

+-----------------------------+
| EXPR$0                      |
+-----------------------------+
| {\"key\":\"va\\lu\'e\r\n\"} |
+-----------------------------+

With NO_BACKSLASH_ESCAPES active, backslashes are no longer treated as escape characters, so the string is returned as-is.