Update exasolrouter documentation

Author: jhnwkmn

maxscale/reference/maxscale-routers/maxscale-exasolrouter.md

@@ -37,6 +37,19 @@ connection_string=127.0.0.1/340F511A5A5179FF44A6828CC140FAEBAF1F2E2ECD73FBCD7EDD
 The latter alternative illustrates the case when the Exasol server uses a
 self-signed certificate.
 
+### `appearance`
+
+* Type: [enum](../../maxscale-management/deployment/maxscale-configuration-guide.md#enumerations)
+* Mandatory: No
+* Dynamic: No
+* Values: `read_only`, `read_write`
+* Default: `read_only`
+
+Specifies how the Exasol router appears to other components of MaxScale.
+
+**Note** Irrespective of the value, the router does not in any way restrict
+what kind of queries can be run through the router.
+
 ### `install_preprocessor_script`
 
 * Type: [boolean](../../maxscale-management/deployment/maxscale-configuration-guide.md#booleans)
@@ -93,6 +106,39 @@ data directory.
 Specifies whether the preprocessor script should be used. If `true`, the
 session creation will fail unless the script is present.
 
+## Transformations
+
+The Exasol Router transparently translates some MariaDB constructs to
+equivalent Exasol constructs.
+
+### `COM_INIT_DB`
+
+The MariaDB COM_INIT_DB packet, using which the default database is changed,
+is transformed into the statement `OPEN SCHEMA <db>`.
+
+### SQL
+
+Currently a transformation will be made **only** if there is an **exact**
+match (apart from case) with the MariaDb SQL. At this point the goal is
+to match what the MariaDB command line client sends.
+
+| MariaDb | Exasol  |
+| ------- | ------- |
+| SELECT @@VERSION_COMMENT LIMIT 1 | SELECT 'Exasol' AS '@@version_comment' LIMIT 1 |
+| SELECT DATABASE() | SELECT TABLE_NAME AS 'Database()' FROM EXA_ALL_TABLES WHERE TABLE_SCHEMA = CURRENT_SCHEMA |
+| SHOW DATABASES | SELECT SCHEMA_NAME AS 'Database' FROM EXA_SCHEMAS ORDER BY SCHEMA_NAME |
+| SHOW TABLES | SELECT TABLE_NAME AS 'Tables' FROM SYS.EXA_ALL_TABLES WHERE TABLE_SCHEMA = CURRENT_SCHEMA ORDER BY TABLE_NAME |
+
+## Limitations
+
+The following is assumed regarding the data returned by Exasol:
+* The value in a column of a row is assumed to be no more than 1024 bytes, and
+* the complete returned result set will fit in a 16MB MariaDB protocol packet.
+
+If these limitations are exceeded, the router may malfunction or crash.
+
+These limitations are temporary and will be removed before Dec 8.
+
 ## SmartRouter
 
 The primary purpose of the Exasol router is to be used together with