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Improved limitations document

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Made the wording of the schemarouter limitations more clear.
This commit is contained in:
Markus Makela 2016-03-09 15:41:59 +02:00
parent 5ad11f2aac
commit 140bd1a3c4
1 changed files with 11 additions and 15 deletions
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Documentation/About/Limitations.md
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@ -34,7 +34,7 @@ Read queries are routed to the master server in the following situations:
### Limitations in multi-statement handling
When a multi-statemet query is executed through the readwritesplit router, it will always
When a multi-statement query is executed through the readwritesplit router, it will always
be routed to the master. With the default configuration, all queries after a
multi-statement query will be routed to the master to prevent possible reads of
false data.
@ -133,26 +133,22 @@ and routed. Here is a list of the current limitations.
the current database in use or to the first available database,
if none of the previous conditions are met.
* Queries without explicit databases that are not session commands
in them are either routed to the current or the first available
database. This means that, for example when creating a new database,
queries should be done directly on the node or the router should
be equipped with the hint filter and a routing hint should be used.
* Temporary tables are only created on the explicit database in the query
or the current database in use. If no database is in use and no database
is explicitly stated, the behavior of the router is undefined.
* Without a default database, queries without explicit databases that do not
modify the session state will be routed the first available server. This
means that, for example when creating a new database, queries should
be done directly on the node or the router should be equipped with
the hint filter and a routing hint should be used. Queries that
modify the session state e.g. `SET autocommit=1` will be routed
to all servers regardless of the default database.
* SELECT queries that modify session variables are not currently supported
because uniform results can not be guaranteed. If such a query is
executed, the behavior of the router is undefined. To work around this
limitation the query must be executed in separate parts.
* Queries targeting databases not mapped by the schemarouter router but
still exist on the database server are not blocked but routed to
the first available server. This possibly returns an error about
database rights instead of a missing database. The behavior of
the router is undefined in this case.
* If a query targets a database the schemarouter hasn't mapped to a server
the query will be routed to the first available server. This possibly
returns an error about database rights instead of a missing database.
## Dbfwfilter limitations