GavinRay97 opened a new issue, #17020:
URL: https://github.com/apache/shardingsphere/issues/17020
# Proposal
I would like to propose adding two new executors to `ShardingSphere Proxy`:
- `Postgres` Frontend, `Calcite` JDBC Executor
- `MySQL` Frontend, `Calcite` JDBC Executor
This would allow using any tool/client that is compatible with either the
MySQL or Postgres wire protocols to query across datasources:
```mermaid
flowchart LR
MySQL_or_PG_Client
subgraph ShardingSphere_Proxy
direction LR
oracle[(Oracle)]
mongo[(Mongo)]
mysql[(MySQL)]
spark[(Spark)]
Calcite_JDBC
Calcite_JDBC<-->oracle
Calcite_JDBC<-->mongo
Calcite_JDBC<-->mysql
Calcite_JDBC<-->spark
end
MySQL_or_PG_Client-. "SELECT ... FROM mysql.db1 \n INNER JOIN oracle.db2
\n INNER JOIN mongo.db3 " .->ShardingSphere_Proxy
```
# Design
> Disclaimer: I have spent a few hours on the source code of ShardingSphere,
but do not understand it very well
- Two new frontend executors should be created:
- `shardingsphere-proxy-frontend-calcite-mysql`
- `shardingsphere-proxy-frontend-calcite-postgres`
- These executors should re-use all of the wire protocol/serialization code
(like the `openGauss` executor does with Postgres)
- What is different is that instead of querying MySQL/PG, the executor will
hold a single internal connection to a `jdbc://calcite` source
- Multiple datasources can be added to this (what Calcite calls) `root
Schema`
- This could be done with YAML configuration or programmatically
IE:
```yaml
dataSources:
calcite_postgres:
# Purposefully empty, this is a virtual schema that exists only
in-memory to aggregate other datasources
url: "jdbc:calcite:fun=postgresql;"
meta:
schemas:
mysql1:
url: jdbc:calcite:schemaType=JDBC;
schema.jdbcUrl=jdbc:mysql://foo:bar@url/db
postgres1:
url: jdbc:calcite:schemaType=JDBC;
schema.jdbcUrl=jdbc:postgresql://baz:qux@url/db
mongo1:
url:
jdbc:calcite:schemaFactory=org.apache.calcite.adapter.mongodb.MongoSchemaFactory;
schema.host=localhost; schema.db=somedb
calcite_mysql:
url: "jdbc:calcite:lex=MYSQL;fun=mysql;"
meta:
schemas:
# ...
```
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