Plan to support information_schema

[RaigorJiang]

Hi community,

We are working on a plan for ShardingSphere-Proxy to support queries on information_schema to resolve some remaining issues. At the same time, this work can also solve the problem that some SQL clients cannot connect to the Proxy.

Since this is an important and complex feature, we need to implement it step by step.

Notice: Some tables or columns are not applicable in distributed scenarios and will not be fully supported.

First, we will start with MySQL.

If you have more related questions or suggestions, please comment in this issue.

Related issues:

• information_schema and sys relevant SQLs can't parse or route #6693
• ShardingSphere cannot resolve information_schema #11992
• Design for MySQL information_schema query #3572

Sample SQLs:

• SELECT SCHEMA_NAME, DEFAULT_CHARACTER_SET_NAME, DEFAULT_COLLATION_NAME FROM information_schema.SCHEMATA
• SELECT COUNT(*) AS support_ndb FROM information_schema.ENGINES WHERE Engine = 'ndbcluster'
• select * from information_schema.columns where table_schema = 'sharding_db';

Supported:

• information_schema.SCHEMATA Support information_schema.schemata query #12011

[lanchengx]

🥷

[RaigorJiang]

Supported by #16234.