system-variables: Merge with tidb-specific-sysvars #3152
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This merges the two documents together.
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ghost
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This has been updated to resolve conflicts from #3215, and is ready for review. |
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@kissmydb, @yikeke, @SunRunAway, @zz-jason, PTAL. |
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Note for the reviewers: shard-row-id-bits.md is added back as a table attribute in #3239 (under review). @kissmydb @zz-jason @SunRunAway |
| - This variable is used to set whether to enable the `TABLE PARTITION` feature. | ||
| - `off` indicates disabling the `TABLE PARTITION` feature. In this case, the syntax that creates a partition table can be executed, but the table created is not a partitioned one. | ||
| - `on` indicates enabling the `TABLE PARTITION` feature for the supported partition types. Currently, it indicates enabling range partition, hash partition and range column partition with one single column. | ||
| - `auto` functions the same way as `on` does. |
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I recall that we have removed the auto value in TiDB 4.0.0, am I correct? @tiancaiamao
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It still seems to work when I set it:
mysql> show global variables like 'tidb_enable_table_partition';
+-----------------------------+-------+
| Variable_name | Value |
+-----------------------------+-------+
| tidb_enable_table_partition | on |
+-----------------------------+-------+
1 row in set (0.01 sec)
mysql> set global tidb_enable_table_partition='auto';
Query OK, 0 rows affected (0.02 sec)
mysql> show global variables like 'tidb_enable_table_partition';
+-----------------------------+-------+
| Variable_name | Value |
+-----------------------------+-------+
| tidb_enable_table_partition | auto |
+-----------------------------+-------+
1 row in set (0.00 sec)
| - Default value: `2` | ||
| - Controls the format version of the newly saved data in the table. In TiDB v4.0, the [new storage row format](https://github.com/pingcap/tidb/blob/master/docs/design/2018-07-19-row-format.md) version `2` is used by default to save new data. | ||
| - If you upgrade from a TiDB version earlier than 4.0.0 to 4.0.0, the format version is not changed, and TiDB continues to use the old format of version `1` to write data to the table, which means that **only newly created clusters use the new data format by default**. | ||
| - Note that modifying this variable does not affect the old data that has been saved, but applies the corresponding version format only to the newly written data after modifying this variable. |
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Can we safely set to a lower value in a newer versioned TiDB cluster? @coocood
| See [TiDB Specific System Variables](/tidb-specific-system-variables.md). | ||
| - Scope: SESSION | GLOBAL | ||
| - Default value: ON | ||
| - This variable controls whether to use the high precision mode when computing the window functions. |
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@SunRunAway Could you help us to explain more on the computing difference between on and off? Would it execute faster when it's set to off?
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There are 3 comments outstanding, but these are actually not new (they existed before the refactor here). Is it possible that we can merge this, and then address in a followup PR? (I have some of my own critiques about some of the descriptions, but I am trying not to mix a refactor with too any changes.) |
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That’s ok to me. |
ghost
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Thanks! I have forked questions to #3260 - we can handle followup from there. |
yikeke
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@kissmydb PTAL |
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Signed-off-by: ti-srebot <[email protected]>
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cherry pick to release-4.0 in PR #3261 |
Signed-off-by: ti-srebot <[email protected]>
ran-huang
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What is changed, added or deleted? (Required)
This PR proposes merging the system-variables and tidb-specific-system-variables documents together.
The motivation for this, is that they both have the same semantics. It is just a namespace that differs, but this can clearly be visible by sorting the variables in alphabetical order (something else I've done.)
In the process of creating this PR, I discovered that several sysvars are undocumented. I have created #3155 to handle separately.
Also,
SHARD_ROW_ID_BITSwas documented as a system variable but it is not. I have moved it to the statement reference forCREATE TABLEandALTER TABLE.Which TiDB version(s) do your changes apply to? (Required)
What is the related PR or file link(s)?
This is original work.