irwinai opened a new issue, #21203:
URL: https://github.com/apache/shardingsphere/issues/21203
## Bug Report
when I do cross schema query ,maybe leads to bug
### Which version of ShardingSphere did you use?
5.1.1
### Which project did you use? ShardingSphere-JDBC or ShardingSphere-Proxy?
ShardingSphere-JDBC
### Expected behavior
query success
### Actual behavior
query failed with exception
### Reason analyze (If you can)
TablesContext#getDatabaseName not right ,can return Optional.empty
RemoveTokenGenerator#isGenerateSQLToken not right,`containsSchemaName` judge
need to be modify
### Steps to reproduce the behavior, such as: SQL to execute, sharding rule
configuration, when exception occur etc.
1. connect to a database with any schema,like `localhost:3306/testDb1`
2. write query like `select id from testDb2.testTable` do cross schema query
so the rewrite engine may get the actual sql like:`select id from
testTable`，the schema has been removed.
the 5.0.0 version is right.
### Example codes for reproduce this issue (such as a github link).
```java
TablesContext
public Optional<String> getDatabaseName() {
// return empty so the query with any schema in actual query usage
return Optional.empty();
}
```
```java
RemoveTokenGenerator
@Override
public boolean isGenerateSQLToken(final SQLStatementContext
sqlStatementContext) {
boolean containsRemoveSegment = false;
if (sqlStatementContext instanceof RemoveAvailable) {
containsRemoveSegment = !((RemoveAvailable)
sqlStatementContext).getRemoveSegments().isEmpty();
}
boolean containsSchemaName = false;
if (sqlStatementContext instanceof TableAvailable) {
TablesContext tablesContext = ((TableAvailable)
sqlStatementContext).getTablesContext();
// ignore sharding multiple schema rewrite sql
containsSchemaName = tablesContext.getDatabaseName().isPresent();
}
return containsRemoveSegment || containsSchemaName;
}
```
anyway,after I modify the code ,I got the right result.
But,this may leads to another proble ,this is `select * from
testDb2.testTable`.
the query with `select * from x` cross schema query may leads to a new
proble,I got code here.
this query may got and NPE with schema is null.
```java
private Collection<ColumnProjection>
getShorthandColumnsFromSimpleTableSegment(final TableSegment table, final
String owner) {
if (!(table instanceof SimpleTableSegment)) {
return Collections.emptyList();
}
String tableName = ((SimpleTableSegment)
table).getTableName().getIdentifier().getValue();
String tableAlias = table.getAlias().orElse(tableName);
Collection<ColumnProjection> result = new LinkedList<>();
if (null == owner) {
schema.getAllColumnNames(tableName).stream().map(columnName ->
new ColumnProjection(tableAlias, columnName, null)).forEach(result::add);
} else if (owner.equalsIgnoreCase(tableAlias)) {
schema.getAllColumnNames(tableName).stream().map(columnName ->
new ColumnProjection(owner, columnName, null)).forEach(result::add);
}
return result;
}
```
which code leads to this new problem?
the SelectStatementContext#getSchema
```java
private ShardingSphereSchema getSchema(final Map<String,
ShardingSphereMetaData> metaDataMap, final String defaultDatabaseName) {
String databaseName =
tablesContext.getDatabaseName().orElse(defaultDatabaseName);
ShardingSphereMetaData metaData = metaDataMap.get(databaseName);
if (null == metaData) {
if (tablesContext.getTables().isEmpty()) {
return new ShardingSphereSchema();
} else {
throw new SchemaNotExistedException(databaseName);
}
}
String schemaName =
tablesContext.getSchemaNames().stream().findFirst().orElse(databaseName);
return metaData.getSchemaByName(schemaName);
}
```
when this code in 5.0.0 like this
```java
private ShardingSphereSchema getSchema(final Map<String,
ShardingSphereMetaData> metaDataMap, final String defaultDatabaseName) {
String schemaName =
tablesContext.getSchemaName().orElse(defaultSchemaName);
ShardingSphereMetaData metaData = metaDataMap.get(schemaName);
if (null == metaData) {
throw new SchemaNotExistedException(schemaName);
}
return metaData.getSchema();
```
So,at last,the new version has a lot of problems,I can't modify the code
anymore....
help me,pls
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