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Document a few more system variables #6492

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Sep 30, 2021
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Document a few more system variables #6492

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7fea7a7
Document a few more system variables
dveeden Sep 16, 2021
b02e351
Plugin vars are instance scoped
dveeden Sep 16, 2021
696e734
Update system-variables.md
dveeden Sep 16, 2021
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Apply suggestions from code review
dveeden Sep 29, 2021
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Merge branch 'master' into missing_sysvars_2
TomShawn Sep 30, 2021
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40 changes: 40 additions & 0 deletions system-variables.md
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Expand Up @@ -193,6 +193,12 @@ mysql> SELECT * FROM t1;
- Default value: `Apache License 2.0`
- This variable indicates the license of your TiDB server installation.

### log_bin

- Scope: NONE
- Default value: `OFF`
- This variable indicates if [TiDB Binlog](/tidb-binlog/tidb-binlog-overview.md) is used.
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### max_execution_time

- Scope: SESSION | GLOBAL
Expand All @@ -205,6 +211,18 @@ mysql> SELECT * FROM t1;
>
> Unlike in MySQL, the `max_execution_time` system variable currently works on all kinds of statements in TiDB, not only restricted to the `SELECT` statement. The precision of the timeout value is roughly 100ms. This means the statement might not be terminated in accurate milliseconds as you specify.

### plugin_dir
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- Scope: SESSION
- Default value: ""
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pingcap/tidb#28084

- The directory to load plugins from as set by the commandline flag.
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### plugin_load

- Scope: SESSION
- Default value: ""
- Wait for loading of named plugins on startup. Plugins are separated by commas. This is set by a commandline flag.
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### port

- Scope: NONE
Expand All @@ -218,6 +236,16 @@ mysql> SELECT * FROM t1;
- Default value: ""
- The local unix socket file that the `tidb-server` is listening on when speaking the MySQL protocol.

### sql_log_bin
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pingcap/tidb#9159


- Scope: SESSION | GLOBAL
- Default value: `ON`
- This indicates if changes should be written to the [TiDB Binlog](/tidb-binlog/tidb-binlog-overview.md) or not.
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> **Note:**
>
> Setting `sql_log_bin` as a global variable is not recommended. Future versions may only allow setting this as a session variable.
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### sql_mode

- Scope: SESSION | GLOBAL
Expand Down Expand Up @@ -1381,6 +1409,18 @@ SET tidb_slow_log_threshold = 200;
- This variable returns the current time zone. Values can be specified as either an offset such as '-8:00' or a named zone 'America/Los_Angeles'.
- The value `SYSTEM` means that the time zone should be the same as the system host, which is available via the [`system_time_zone`](#system_time_zone) variable.

### timestamp

- Scope: SESSION
- Default value: ""
- If set to a non-empty value this is the UNIX epoch that is used as timestamp for `CURRENT_TIMESTAMP()`, `NOW()` and other functions. This can be used when restoring or replicating data.
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### tmp_table_size
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This variable is deleted in #6775.


- Scope: SESSION | GLOBAL
- Default value: 16777216
- The maximum size of a temporary table in bytes
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### transaction_isolation

- Scope: SESSION | GLOBAL
Expand Down