system-databases: Refactor/Improve clarity (pingcap#3178)

* WIP - refactor system tables

* Add missing items

* WIP

* Add redirects from old locations

* Split information_schema table

* Remove category meta data from files

* Update .github/assign-by-files.yml

Co-authored-by: Keke Yi <[email protected]>

* Update information-schema.md

Co-authored-by: Keke Yi <[email protected]>

* Update information-schema/information-schema-metrics-tables.md

Co-authored-by: Keke Yi <[email protected]>

* Update mysql-schema.md

Co-authored-by: Keke Yi <[email protected]>

* Update mysql-schema.md

Co-authored-by: Keke Yi <[email protected]>

* Manual merge conflicts from master

* Update information-schema/information-schema-collations.md

Co-authored-by: Zhang Jian <[email protected]>

* Update information-schema/information-schema-collation-character-set-applicability.md

Co-authored-by: Zhang Jian <[email protected]>

Co-authored-by: Keke Yi <[email protected]>
Co-authored-by: Zhang Jian <[email protected]>

Author: 3 people

.github/assign-by-files.yml

@@ -83,9 +83,9 @@
 #   - TomShawn
 #   - 
 
-# 'system-tables/**/*.md':
-#   - TomShawn
-#   - 
+'information-schema/**/*.md':
+  - TomShawn
+  - nullnotnil
 
 'ticdc/**/*.md':
   - WangXiangUSTC

TOC.md

@@ -81,7 +81,7 @@
 + Troubleshoot
   + [TiDB Troubleshooting Map](/tidb-troubleshooting-map.md)
   + [Identify Slow Queries](/identify-slow-queries.md)
-  + [SQL Diagnostics](/system-tables/system-table-sql-diagnostics.md)
+  + [SQL Diagnostics](/information-schema/information-schema-sql-diagnostics.md)
   + [Identify Expensive Queries](/identify-expensive-queries.md)
   + [Statement Summary Tables](/statement-summary-tables.md)
   + [Troubleshoot Hotspot Issues](/troubleshoot-hot-spot-issues.md)
@@ -378,20 +378,48 @@
     + [Partitioning](/partitioned-table.md)
     + [Character Set and Collation](/character-set-and-collation.md)
     + System Tables
-      + [`mysql`](/system-tables/system-table-overview.md)
-      + [`information_schema`](/system-tables/system-table-information-schema.md)
-      + sql-diagnosis
-        + [`cluster_info`](/system-tables/system-table-cluster-info.md)
-        + [`cluster_hardware`](/system-tables/system-table-cluster-hardware.md)
-        + [`cluster_config`](/system-tables/system-table-cluster-config.md)
-        + [`cluster_load`](/system-tables/system-table-cluster-load.md)
-        + [`cluster_systeminfo`](/system-tables/system-table-cluster-systeminfo.md)
-        + [`cluster_log`](/system-tables/system-table-cluster-log.md)
-        + [`metrics_schema`](/system-tables/system-table-metrics-schema.md)
-        + [`metrics_tables`](/system-tables/system-table-metrics-tables.md)
-        + [`metrics_summary`](/system-tables/system-table-metrics-summary.md)
-        + [`inspection_result`](/system-tables/system-table-inspection-result.md)
-        + [`inspection_summary`](/system-tables/system-table-inspection-summary.md)
+      + [`mysql`](/mysql-schema.md)
+      + `INFORMATION_SCHEMA`
+        + [Overview](/information-schema.md)
+        + [`ANALYZE_STATUS`](/information-schema/information-schema-analyze-status.md)
+        + [`CHARACTER_SETS`](/information-schema/information-schema-character-sets.md)
+        + [`CLUSTER_CONFIG`](/information-schema/information-schema-cluster-config.md)
+        + [`CLUSTER_HARDWARE`](/information-schema/information-schema-cluster-hardware.md)
+        + [`CLUSTER_INFO`](/information-schema/information-schema-cluster-info.md)
+        + [`CLUSTER_LOAD`](/information-schema/information-schema-cluster-load.md)
+        + [`CLUSTER_LOG`](/information-schema/information-schema-cluster-log.md)
+        + [`CLUSTER_SYSTEMINFO`](/information-schema/information-schema-cluster-systeminfo.md)
+        + [`COLLATIONS`](/information-schema/information-schema-collations.md)
+        + [`COLLATION_CHARACTER_SET_APPLICABILITY`](/information-schema/information-schema-collation-character-set-applicability.md)
+        + [`COLUMNS`](/information-schema/information-schema-columns.md)
+        + [`DDL_JOBS`](/information-schema/information-schema-ddl-jobs.md)
+        + [`ENGINES`](/information-schema/information-schema-engines.md)
+        + [`INSPECTION_RESULT`](/information-schema/information-schema-inspection-result.md)
+        + [`INSPECTION_RULES`](/information-schema/information-schema-inspection-rules.md)
+        + [`INSPECTION_SUMMARY`](/information-schema/information-schema-inspection-summary.md)
+        + [`KEY_COLUMN_USAGE`](/information-schema/information-schema-key-column-usage.md)
+        + [`METRICS_SUMMARY`](/information-schema/information-schema-metrics-summary.md)
+        + [`METRICS_TABLES`](/information-schema/information-schema-metrics-tables.md)
+        + [`PARTITIONS`](/information-schema/information-schema-partitions.md)
+        + [`PROCESSLIST`](/information-schema/information-schema-processlist.md)
+        + [`SCHEMATA`](/information-schema/information-schema-schemata.md)
+        + [`SEQUENCES`](/information-schema/information-schema-sequences.md)
+        + [`SESSION_VARIABLES`](/information-schema/information-schema-session-variables.md)
+        + [`SLOW_QUERY`](/information-schema/information-schema-slow-query.md)
+        + [`STATISTICS`](/information-schema/information-schema-statistics.md)
+        + [`TABLES`](/information-schema/information-schema-tables.md)
+        + [`TABLE_CONSTRAINTS`](/information-schema/information-schema-table-constraints.md)
+        + [`TABLE_STORAGE_STATS`](/information-schema/information-schema-table-storage-stats.md)
+        + [`TIDB_HOT_REGIONS`](/information-schema/information-schema-tidb-hot-regions.md)
+        + [`TIDB_INDEXES`](/information-schema/information-schema-tidb-indexes.md)
+        + [`TIDB_SERVERS_INFO`](/information-schema/information-schema-tidb-servers-info.md)
+        + [`TIFLASH_REPLICA`](/information-schema/information-schema-tiflash-replica.md)
+        + [`TIKV_REGION_PEERS`](/information-schema/information-schema-tikv-region-peers.md)
+        + [`TIKV_REGION_STATUS`](/information-schema/information-schema-tikv-region-status.md)
+        + [`TIKV_STORE_STATUS`](/information-schema/information-schema-tikv-store-status.md)
+        + [`USER_PRIVILEGES`](/information-schema/information-schema-user-privileges.md)
+        + [`VIEWS`](/information-schema/information-schema-views.md)
+      + [`METRICS_SCHEMA`](/metrics-schema.md)
   + UI
     + TiDB Dashboard
       + [Overview](/dashboard/dashboard-intro.md)

_index.md

@@ -78,7 +78,7 @@ Designed for the cloud, TiDB provides flexible scalability, reliability and secu
 
 - [TiDB Troubleshooting Map](/tidb-troubleshooting-map.md)
 - [Identify Slow Queries](/identify-slow-queries.md)
-- [SQL Diagnostics](/system-tables/system-table-sql-diagnostics.md)
+- [SQL Diagnostics](/information-schema/information-schema-sql-diagnostics.md)
 - [Troubleshoot Hotspot Issues](/troubleshoot-hot-spot-issues.md)
 - [Troubleshoot the TiDB Cluster](/troubleshoot-tidb-cluster.md)
 - [Troubleshoot TiCDC](/ticdc/troubleshoot-ticdc.md)

check-cluster-status-using-sql-statements.md

@@ -10,18 +10,18 @@ TiDB offers some SQL statements and system tables to check the TiDB cluster stat
 
 The `INFORMATION_SCHEMA` system database offers system tables as follows to query the cluster status and diagnose common cluster issues:
 
-- [`TABLES`](/system-tables/system-table-information-schema.md#tables-table)
-- [`TIDB_INDEXES`](/system-tables/system-table-information-schema.md#tidb_indexes-table)
-- [`ANALYZE_STATUS`](/system-tables/system-table-information-schema.md#analyze_status-table)
-- [`TIDB_HOT_REGIONS`](/system-tables/system-table-information-schema.md#tidb_hot_regions-table)
-- [`TIKV_STORE_STATUS`](/system-tables/system-table-information-schema.md#tikv_store_status-table)
-- [`TIKV_REGION_STATUS`](/system-tables/system-table-information-schema.md#tikv_region_status-table)
-- [`TIKV_REGION_PEERS`](/system-tables/system-table-information-schema.md#tikv_region_peers-table)
+- [`TABLES`](/information-schema/information-schema-tables.md)
+- [`TIDB_INDEXES`](/information-schema/information-schema-tidb-indexes.md)
+- [`ANALYZE_STATUS`](/information-schema/information-schema-analyze-status.md)
+- [`TIDB_HOT_REGIONS`](/information-schema/information-schema-tidb-hot-regions.md)
+- [`TIKV_STORE_STATUS`](/information-schema/information-schema-tikv-store-status.md)
+- [`TIKV_REGION_STATUS`](/information-schema/information-schema-tikv-region-status.md)
+- [`TIKV_REGION_PEERS`](/information-schema/information-schema-tikv-region-peers.md)
 
 You can also use the following statements to obtain some useful information for troubleshooting and querying the TiDB cluster status.
 
 - `ADMIN SHOW DDL`: obtains the ID of TiDB with the `DDL owner` role and `IP:PORT`.
-- The feature of `SHOW ANALYZE STATUS` is the same with that of [the `ANALYZE_STATUS` table](/system-tables/system-table-information-schema.md#analyze_status-table).
+- The feature of `SHOW ANALYZE STATUS` is the same with that of [the `ANALYZE_STATUS` table](/information-schema/information-schema-analyze-status.md).
 - Specific `EXPLAIN` statements
     - `EXPLAIN ANALYZE`: obtains some detailed information for execution of a SQL statement.
     - `EXPLAIN FOR CONNECTION`: obtains the execution plan for the query executed last in a connection. Can be used along with `SHOW PROCESSLIST`.

dashboard/dashboard-diagnostics-report.md

@@ -62,7 +62,7 @@ The fields in the table above are described as follows:
 
 #### Cluster Topology Info
 
-The `Cluster Info` table shows the cluster topology information. The information in this table are from TiDB [information_schema.cluster_info](/system-tables/system-table-cluster-info.md) system table.
+The `Cluster Info` table shows the cluster topology information. The information in this table are from TiDB [information_schema.cluster_info](/information-schema/information-schema-cluster-info.md) system table.
 
 ![Cluster info](/media/dashboard/dashboard-diagnostics-cluster-info.png)
 
@@ -78,7 +78,7 @@ The fields in the table above are described as follows:
 
 ### Diagnostic information
 
-TiDB has built-in automatic diagnostic results. For the description of each field, see [information_schema.inspection-result](/system-tables/system-table-inspection-result.md) system table.
+TiDB has built-in automatic diagnostic results. For the description of each field, see [information_schema.inspection-result](/information-schema/information-schema-inspection-result.md) system table.
 
 ### Load Info
 

faq/tidb-faq.md

@@ -540,7 +540,7 @@ No. Currently, TiDB only supports the distributed storage engine and the Golevel
 
 #### Can the `Information_schema` support more real information?
 
-As part of MySQL compatibility, TiDB supports a number of `INFORMATION_SCHEMA` tables. Many of these tables also have a corresponding SHOW command. For more information, see [Information Schema](/system-tables/system-table-information-schema.md).
+As part of MySQL compatibility, TiDB supports a number of `INFORMATION_SCHEMA` tables. Many of these tables also have a corresponding SHOW command. For more information, see [Information Schema](/information-schema.md).
 
 #### What's the explanation of the TiDB Backoff type scenario?
 

identify-slow-queries.md

@@ -106,7 +106,7 @@ TiKV Coprocessor Task fields:
 
 ## Memory mapping in slow log
 
-You can query the content of the slow query log by querying the `INFORMATION_SCHEMA.SLOW_QUERY` table. Each column name in the table corresponds to one field name in the slow log. For table structure, see the introduction to the `SLOW_QUERY` table in [Information Schema](/system-tables/system-table-information-schema.md#information-schema).
+You can query the content of the slow query log by querying the `INFORMATION_SCHEMA.SLOW_QUERY` table. Each column name in the table corresponds to one field name in the slow log. For table structure, see the introduction to the `SLOW_QUERY` table in [Information Schema](/information-schema/information-schema-slow-query.md).
 
 > **Note:**
 >
@@ -158,7 +158,7 @@ For TiDB 4.0, `SLOW_QUERY` supports querying the slow log of any period of time,
 >
 > If the slow log files of the specified time range are removed, or there is no slow query, the query returns NULL.
 
-TiDB 4.0 adds the [`CLUSTER_SLOW_QUERY`](/system-tables/system-table-information-schema.md#cluster_slow_query-table) system table to query the slow query information of all TiDB nodes. The table schema of the `CLUSTER_SLOW_QUERY` table differs from that of the `SLOW_QUERY` table in that an `INSTANCE` column is added to `CLUSTER_SLOW_QUERY`. The `INSTANCE` column represents the TiDB node address of the row information on the slow query. You can use `CLUSTER_SLOW_QUERY` the way you do with [`SLOW_QUERY`](/system-tables/system-table-information-schema.md#slow_query-table).
+TiDB 4.0 adds the [`CLUSTER_SLOW_QUERY`](/information-schema/information-schema-slow-query.md#cluster_slow_query-table) system table to query the slow query information of all TiDB nodes. The table schema of the `CLUSTER_SLOW_QUERY` table differs from that of the `SLOW_QUERY` table in that an `INSTANCE` column is added to `CLUSTER_SLOW_QUERY`. The `INSTANCE` column represents the TiDB node address of the row information on the slow query. You can use `CLUSTER_SLOW_QUERY` the way you do with [`SLOW_QUERY`](/information-schema/information-schema-slow-query.md).
 
 When you query the `CLUSTER_SLOW_QUERY` table, TiDB pushes the computation and the judgment down to other nodes, instead of retrieving all slow query information from other nodes and executing the operations on one TiDB node.