align pingcap/docs-cn#3770

pingcap · Jul 10, 2020 · 175c6cf · 175c6cf
1 parent e7bf6e2
commit 175c6cf
Show file tree

Hide file tree

Showing 5 changed files with 27 additions and 3 deletions.
diff --git a/TOC.md b/TOC.md
@@ -203,6 +203,7 @@
       + Attributes
         + [AUTO_INCREMENT](/auto-increment.md)
         + [AUTO_RANDOM](/auto-random.md)
+        + [SHARD_ROW_ID_BITS](/shard-row-id-bits.md)
       + [Literal Values](/literal-values.md)
       + [Schema Object Names](/schema-object-names.md)
       + [Keywords and Reserved Words](/keywords.md)

diff --git a/best-practices/high-concurrency-best-practices.md b/best-practices/high-concurrency-best-practices.md
@@ -181,7 +181,7 @@ In this case, the table is simple. In other cases, you might also need to consid
 
 **Problem one:**
 
-If a table does not have a primary key, or the primary key is not the `Int` type and you do not want to generate a randomly distributed primary key ID, TiDB provides an implicit `_tidb_rowid` column as the row ID. Generally, when you do not use the `SHARD_ROW_ID_BITS` parameter, the values of the `_tidb_rowid` column are also monotonically increasing, which might causes hotspots too. Refer to [`SHARD_ROW_ID_BITS` description](/tidb-specific-system-variables.md#shard_row_id_bits) for more details.
+If a table does not have a primary key, or the primary key is not the `Int` type and you do not want to generate a randomly distributed primary key ID, TiDB provides an implicit `_tidb_rowid` column as the row ID. Generally, when you do not use the `SHARD_ROW_ID_BITS` parameter, the values of the `_tidb_rowid` column are also monotonically increasing, which might causes hotspots too. Refer to [`SHARD_ROW_ID_BITS` description](/shard-row-id-bits.md) for more details.
 
 To avoid the hotspot problem in this situation, you can use `SHARD_ROW_ID_BITS` and `PRE_SPLIT_REGIONS` when creating a table. For more details about `PRE_SPLIT_REGIONS`, refer to [Pre-split Regions](/sql-statements/sql-statement-split-region.md#pre_split_regions).
 

diff --git a/faq/tidb-faq.md b/faq/tidb-faq.md
@@ -1089,7 +1089,7 @@ See [The TiDB Command Options](/command-line-flags-for-tidb-configuration.md).
 
 #### How to scatter the hotspots?
 
-In TiDB, data is divided into Regions for management. Generally, the TiDB hotspot means the Read/Write hotspot in a Region. In TiDB, for the table whose primary key (PK) is not an integer or which has no PK, you can properly break Regions by configuring `SHARD_ROW_ID_BITS` to scatter the Region hotspots. For details, see the introduction of `SHARD_ROW_ID_BITS` in [TiDB Specific System Variables and Syntax](/tidb-specific-system-variables.md#shard_row_id_bits).
+In TiDB, data is divided into Regions for management. Generally, the TiDB hotspot means the Read/Write hotspot in a Region. In TiDB, for the table whose primary key (PK) is not an integer or which has no PK, you can properly break Regions by configuring `SHARD_ROW_ID_BITS` to scatter the Region hotspots. For details, see the introduction of `SHARD_ROW_ID_BITS` in [TiDB Specific System Variables and Syntax](/shard-row-id-bits.md).
 
 ### TiKV
 

diff --git a/shard-row-id-bits.md b/shard-row-id-bits.md
@@ -0,0 +1,23 @@
+---
+title: SHARD_ROW_ID_BITS
+summary: Learn the SHARD_ROW_ID_BITS attribute.
+---
+
+# SHARD_ROW_ID_BITS
+
+This document introduces the `SHARD_ROW_ID_BITS` table attribute, which is used to set the number of bits of the implicit sharded `_tidb_rowid`.
+
+## Concept
+
+For the tables with a non-integer primary key or no primary key, TiDB uses an implicit auto-increment row ID. When a large number of `INSERT` operations are performed, the data is written into a single Region, causing a write hot spot.
+
+To mitigate the hot spot issue, you can configure `SHARD_ROW_ID_BITS`. The row IDs are scattered and the data are written into multiple different Regions. But setting an overlarge value might lead to an excessively large number of RPC requests, which increases the CPU and network overheads.
+
+- `SHARD_ROW_ID_BITS = 4` indicates 16 shards
+- `SHARD_ROW_ID_BITS = 6` indicates 64 shards
+- `SHARD_ROW_ID_BITS = 0` indicates the default 1 shard
+
+## Examples
+
+- `CREATE TABLE`: `CREATE TABLE t (c int) SHARD_ROW_ID_BITS = 4;`
+- `ALTER TABLE`: `ALTER TABLE t SHARD_ROW_ID_BITS = 4;`
diff --git a/sql-statements/sql-statement-create-table.md b/sql-statements/sql-statement-create-table.md
@@ -225,7 +225,7 @@ table_option:
   | STATS_PERSISTENT [=] {DEFAULT|0|1}
 ```
 
-The `table_option` currently only supports `AUTO_INCREMENT`, `SHARD_ROW_ID_BITS` (see [TiDB Specific System Variables](/tidb-specific-system-variables.md#shard_row_id_bits) for details), `PRE_SPLIT_REGIONS`, `CHARACTER SET`, `COLLATE`, and `COMMENT`, while the others are only supported in syntax. The clauses are separated by a comma `,`. See the following table for details:
+The `table_option` currently only supports `AUTO_INCREMENT`, `SHARD_ROW_ID_BITS` (see [TiDB Specific System Variables](/shard-row-id-bits.md) for details), `PRE_SPLIT_REGIONS`, `CHARACTER SET`, `COLLATE`, and `COMMENT`, while the others are only supported in syntax. The clauses are separated by a comma `,`. See the following table for details:
 
 | Parameters | Description | Example |
 | ---------- | ---------- | ------- |