[GitHub] [incubator-shardingsphere] ssxlulu opened a new issue #3572: Design for MySQL information_schema query

[GitBox <gi...@apache.org>]

ssxlulu opened a new issue #3572: Design for MySQL information_schema query
URL: https://github.com/apache/incubator-shardingsphere/issues/3572
 
 
   Query from information_schema is a common scene, some MySQL management client like Navicat will send such queries at the beginning of connection to ShardingSphere.
   
   But ShardingSphere doesn't support information_schema query well for now.
   
   For example, Navicat will send the following sql to SS:
   
   `SELECT COUNT(*) FROM information_schema.TABLES WHERE TABLE_SCHEMA = 'sharding_db' UNION SELECT COUNT(*) FROM information_schema.COLUMNS WHERE TABLE_SCHEMA
    = 'sharding_db' UNION SELECT COUNT(*) FROM information_schema.ROUTINES WHERE ROU
   TINE_SCHEMA = 'sharding_db';`
   
   But this sql will cause NPE exception for SS:
   
   ```
   java.lang.NullPointerException: null
   	at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.datasource.JDBCBackendDataSource.createConnection(JDBCBackendDataSource.java:150)
   	at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.datasource.JDBCBackendDataSource.getConnections(JDBCBackendDataSource.java:123)
   	at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.connection.BackendConnection.getConnectionFromUnderlying(BackendConnection.java:198)
   	at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.connection.BackendConnection.getConnectionsWithoutTransaction(BackendConnection.java:181)
   	at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.connection.BackendConnection.getConnections(BackendConnection.java:150)
   	at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.execute.callback.ProxyJDBCExecutePrepareCallback.getConnections(ProxyJDBCExecutePrepareCallback.java:56)
   	at org.apache.shardingsphere.core.execute.sql.prepare.SQLExecutePrepareTemplate.getSQLExecuteGroups(SQLExecutePrepareTemplate.java:89)
   	at org.apache.shardingsphere.core.execute.sql.prepare.SQLExecutePrepareTemplate.getSynchronizedExecuteUnitGroups(SQLExecutePrepareTemplate.java:67)
   	at org.apache.shardingsphere.core.execute.sql.prepare.SQLExecutePrepareTemplate.getExecuteUnitGroups(SQLExecutePrepareTemplate.java:59)
   	at org.apache.shardingsphere.shardingproxy.backend.communication.jdbc.execute.JDBCExecuteEngine.execute(JDBCExecuteEngine.java:80)
   ……
   ```
   
   What's more, Navicat will not only send one sql, above is just an example.
   
   

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