sql: add a note about FULLTEXT

sql-statements/sql-statement-add-index.md

@@ -85,7 +85,9 @@ mysql> EXPLAIN SELECT * FROM t1 WHERE c1 = 3;
 
 ## MySQL compatibility
 
-* `FULLTEXT`, `HASH` and `SPATIAL` indexes are not supported.
+* TiDB accepts index types such as `HASH`, `BTREE` and `RTREE` in syntax for compatibility with MySQL, but ignores them.
+* `SPATIAL` indexes are not supported.
+* TiDB supports parsing the `FULLTEXT` syntax but does not support using the `FULLTEXT` indexes.
 * Descending indexes are not supported (similar to MySQL 5.7).
 * Adding the primary key of the `CLUSTERED` type to a table is not supported. For more details about the primary key of the `CLUSTERED` type, refer to [clustered index](/clustered-indexes.md).
 

sql-statements/sql-statement-alter-table.md

@@ -39,7 +39,7 @@ AlterTableSpec ::=
 |   'ORDER' 'BY' AlterOrderItem ( ',' AlterOrderItem )*
 |   ( 'DISABLE' | 'ENABLE' ) 'KEYS'
 |   ( 'MODIFY' ColumnKeywordOpt IfExists | 'CHANGE' ColumnKeywordOpt IfExists ColumnName ) ColumnDef ColumnPosition
-|   'ALTER' ( ColumnKeywordOpt ColumnName ( 'SET' 'DEFAULT' ( SignedLiteral | '(' Expression ')' ) | 'DROP' 'DEFAULT' ) | 'CHECK' Identifier EnforcedOrNot | 'INDEX' Identifier IndexInvisible )
+|   'ALTER' ( ColumnKeywordOpt ColumnName ( 'SET' 'DEFAULT' ( SignedLiteral | '(' Expression ')' ) | 'DROP' 'DEFAULT' ) | 'CHECK' Identifier EnforcedOrNot | 'INDEX' Identifier ("VISIBLE" | "INVISIBLE") )
 |   'RENAME' ( ( 'COLUMN' | KeyOrIndex ) Identifier 'TO' Identifier | ( 'TO' | '='? | 'AS' ) TableName )
 |   LockClause
 |   AlgorithmClause

sql-statements/sql-statement-create-index.md

@@ -43,7 +43,7 @@ IndexOption ::=
 |   IndexType
 |   'WITH' 'PARSER' Identifier
 |   'COMMENT' stringLit
-|   IndexInvisible
+|   ("VISIBLE" | "INVISIBLE")
 
 IndexTypeName ::=
     'BTREE'
@@ -349,7 +349,8 @@ The system variables associated with the `CREATE INDEX` statement are `tidb_ddl_
 
 ## MySQL compatibility
 
-* TiDB supports parsing the `FULLTEXT` and `SPATIAL` syntax but does not support using the `FULLTEXT`, `HASH`, and `SPATIAL` indexes.
+* TiDB supports parsing the `FULLTEXT` syntax but does not support using the `FULLTEXT`, `HASH`, and `SPATIAL` indexes.
+* TiDB accepts index types such as `HASH`, `BTREE` and `RTREE` in syntax for compatibility with MySQL, but ignores them.
 * Descending indexes are not supported (similar to MySQL 5.7).
 * Adding the primary key of the `CLUSTERED` type to a table is not supported. For more details about the primary key of the `CLUSTERED` type, refer to [clustered index](/clustered-indexes.md).
 * Expression indexes are incompatible with views. When a query is executed using a view, the expression index cannot be used at the same time.

sql-statements/sql-statement-create-table.md

@@ -76,6 +76,7 @@ KeyPart ::=
 IndexOption ::=
     'COMMENT' String
 |   ( 'VISIBLE' | 'INVISIBLE' )
+|   ('USING' | 'TYPE') ('BTREE' | 'RTREE' | 'HASH')
 
 ForeignKeyDef
          ::= ( 'CONSTRAINT' Identifier )? 'FOREIGN' 'KEY'
@@ -239,7 +240,8 @@ mysql> DESC t1;
 ## MySQL compatibility
 
 * All of the data types except spatial types are supported.
-* `FULLTEXT`, `HASH` and `SPATIAL` indexes are not supported.
+* TiDB accepts index types such as `HASH`, `BTREE` and `RTREE` in syntax for compatibility with MySQL, but ignores them.
+* TiDB supports parsing the `FULLTEXT` syntax but does not support using the `FULLTEXT` indexes.
 
 <CustomContent platform="tidb">
 

sql-statements/sql-statement-show-indexes.md

@@ -53,6 +53,8 @@ mysql> SHOW KEYS FROM t1;
 2 rows in set (0.00 sec)
 ```
 
+Note that TiDB accepts index types such as `HASH`, `BTREE` and `RTREE` in syntax for compatibility with MySQL, but ignores them.
+
 ## MySQL compatibility
 
 The `SHOW INDEXES [FROM|IN]` statement in TiDB is fully compatible with MySQL. If you find any compatibility differences, [report a bug](https://docs.pingcap.com/tidb/stable/support).